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Machined Surface Quality in Nano Aluminum Mixed Electrical Discharge Machining

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Abstract

The development of implants in biomedical engineering application nowadays requires materials with good mechanical and physical properties. Conventional machining of high strength alloy materials is a challenge. Non-conventional machining processes such as electrical discharge machining (EDM) of high strength material have its limitations. Among the limitations are surface modification, induced corrosion, residual stress and reducing of fatigue performance during the EDM process. Nano aluminum mixed electrical discharge machining (PMEDM) is envisaged able to address some of the above mentioned problems. In this study, PMEDM machining performance on biomedical grade titanium alloy workpiece using nano aluminum powder is assessed to establish its improvement for biomedical application. The characteristics analyzed are surface roughness (Ra) and surface morphology. Process variable machining parameters used are peak current, ON-time (pulse duration), gap voltage and nano aluminum concentration. Results of nano aluminum PMEDM on titanium alloy material show slight improvement in terms of surface roughness (Ra) and surface morphology as compared to conventional EDM. PMEDM results show fewer defects in terms of cracks, craters and voids.
2351-9789 © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of SMPM 2017
doi: 10.1016/j.promfg.2016.12.061
Procedia Manufacturing 7 (2017) 510 – 517
Available online at www.sciencedirect.com
ScienceDirect
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© 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of SMPM 2017
511
A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517

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  +  +   FG -9   )   
+ -33333))
#DFG()) ))+ +,
   )) *  ) # ,
 #+  >    )     , -
) ) -   # )  )   +,  7 
 ) 7))   
5,    ))  7 + 
),10)99 +&H2#
H2F!G () ) 3 0 )* 
)))  7)))+
++ 2)FCG)  ))- 
 + +,(),+))- ,))
)  +,
()+7-) ),))
 ) ) )  )  9 )         #
#)) ),F"G*,)))7 +D
- ))))  ) +) +   )  FG 
 )- 3   )3   +,    + 3 )3
- > ()
-  )  )    -FGI7J   F%G
   F&G  ) - )  )      )  )  
,
(  ) + - 3   9   ) )
-), )0  -),  
)-),* )) 7))+() 7
+)   )), 7
73   ) 7 ) F$G - +, ) ) 
    =  
 +#+ +,+ + , ) K3
) +D  ) ),   3 ,  ,)0 -  + 
,: ),)

-@9))
-@-))
:@*)
512 A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517

-9     #7 -  ) (#*#C/ 7  )  # 
()(#*#C/7  09$ 9" )7)) )
-) !* 7)) ++)
*,)) 7
9 ) )   ),    
 )   -  )  ,  +     
)  ):3   ,L-- ,
) ),())  (+
(+-) 
  M ,+ :
72 F*G 1  %#"
= /
F/G
= /
&#"
?6#( FNG ?6 C#&
?LL# FNG ?LL &
6  
0  C
6 
 FG  !
O7  (#*#C/
- 2 #

)!)&,&
LL )):--+
, ,L )1 3?6# ::))
1?6#,)): ),) &
/+"/()+))), ) ,
)))7 :5,7P7QFG))
)) 7    ))  )   )) )   ) 7  

1+,L): ))-) )
-+)))),+),
) 7()),)):)13+)
1 : ) 1 %* "*:   ?6#3   
) O) 3)) 
 :  - ,  L  :    - 
,+!&CR :-,
513
A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517
L:-,)
L:-,)
))&,(
-,     , -   ) )0     , 
 #  L! L!+  ,L C))  ),
 )    , (#*#C/ 7   -   L C  )) )
< )  
)))LC
K)) 
)))LC+
<) 
)))L
K)) 
)))L+
514 A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517
 L C+     L  23   #7     
)))31 3?6#= )LC+6#+)
LC++ ))) -) )))
 +  ))  ) ,   )   #)  7

 
L!- ,3+ #
  
LC ),<) B1 S%*3?6SC3= /S&/3+K)) B1 S"*3?6#
S&T3= /S"/
:)+   + )+   ) + FG
))   +)++ 
23   #7      )     F%G -,#
   ,,  -)  +) L "  )) L "+ )
,),++39,3 3 ,
) ,7  )L!()+) )
  ) #    L !+ ))  ,  -
))# +&H2H2#) 7+
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A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517
+ O) + ) ,+, )) ,) + 
+  )  , )     7  ()  +
), 

L"--,@<) @1 S%*3?6SCT3= /S&/3+K)) @1 S"*3
?6S&T3= /S"/
 
L ),-,)@@1 S%*3?6SCT3= /S&/3S3+@
1 S"*3?6#S&T3= /S"/3S!
L  ) )  ),  )  )     L   )) L +
)+L ) )))
   ()    )   ,  ))      )
7  )  - 6  9  ) #7  )
-)69)+)
, )7 + 0 )) L%
) -  ) )L% )) L%+ 
)  *   - ) 3      
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+
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516 A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517
7 - 1+ )   33 + 9,* +3
     ))  (), , )
73+ ))  ,) 

L%--,<) @1 S%*3?6SCT3= /S&/3S3+
K)) @1 S"*3?6S&T3= /S"/3S!
'
1)))- ) >,),
+ - ) )3 #73  ))
() + ,  +  
   ) )  ()  + )  ,    )
 ), )L) ,) 
+ )  +)) -
+
()"
*)  7  7 )     ) ) 7  M (7
-(:?6*M(
!
FG K:*.)3U2, + +,3U&9
%3 !#3
FG .V3:7353345 W3U  # 
)<-6),3U:)))&,)!3 C#"3$
F!G K-#K,3$$3$$(*$@=K3"
FCG #< 2)3 #K <3 2#2 2)3  5#< ?3 U-  #) + + ,  
3U:&,($+&$C"3 C!#C&3&
F"G L 573  )3 * 573  /3  * 5 3 U1  - ) )  .+
). +,3U$+%"3 &&#$!3!
FG 4I7J34W73K+3.73<O3U() (*C/
,-   ) 3U:&, *,*$
C3 $""#$3
+

(
+
(
+
517
A.M. Abdul-Rani et al. / Procedia Manufacturing 7 (2017) 510 – 517
F%G 4I7J3 4KX7I3 <.WI7I3 K+3 )3 4W73 U2)0 ))3
+>) )#    )  3U $&,  &3 %!#%&3
!
F&G = 3 )73  *:D73 U.  @2   # 3U 
+3 C#"C3
F$G Y#L(02#Y<3U- ))),3U%:&,
$$&,&(%3 "&#"$3
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... The research outcome claims that the mixture of MWCNT/HAp produces enhanced biocompatibility and surface integrity due to the uniform spark propagation during the machining process. Abdul-Rani et al. [71] analyzed the treated surface of Ti-alloy in terms of surface roughness and morphology by employing tungsten and copper as a tool and nano-Al particles as an additive to the dielectric fluid. The addition of nano-Al powder by 3 g/L provided an exceptional increase in surface roughness by about 38.46% due to its high conductivity. ...
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Since the inception of electric discharge machining (EDM), it has facilitated the production industries, for instance, die & mold, automotive, aerospace, etc., by providing an effective solution for machining hard-to-cut materials and intricate geometries. However, achieving high machining rates and a fine surface finish is an inherent issue with the traditional EDM process. The emergence of the powder mixed electric discharge machining (PMEDM) process has not only provided the opportunity for enhancing productivity and surface finish but also opened a window for its potential application in surface modification/coating of biomaterials. The process incorporates simultaneous machining and coating of bioimplants, i.e., lacking in the already available chemical and physical coating methods while requiring costly post-treatment procedures. This study comprehends the influence of powder characteristics and EDM process parameters on the performance parameters. The impact of tool electrodes and additive powders on the machined and coated surface of commonly used biomaterials. Furthermore, the study depicts the most frequently used methods for optimizing the PMEDM process, future research directions, challenges, and research trends over the past decade.
... Abdul-Rani AM et al. [10] made a PMEDC process with nano powder shows a better surface finish with lesser defects. Prakash C et al. [11] developed a coating with bioactive material like hydroxyapatite by the PMEDC process, and improved the substrate's biological response. ...
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This paper reports solid lubricant coating on the M2 high-speed steel substrate with MoS2:Cu (50:50) green compact electrode by electric discharge coating (EDC) process. The influence of input parameters (peak current(I) and pulse duration(ton)) on the coating responses (thickness, microhardness, and surface roughness) have been investigated. The coated materials atomic weight percentage and chemical compounds are examined through EDS and XRD analysis. The maximum coating thickness (695.3µm) reported at ton - 750 µs and I- 5A. The coated samples microhardness exhibit between 217.8 HV – 669.43 HV, which is lesser than the substrate (750 HV). The adhesive strength of the coating surface was examined using scratch test with progressive load. The result shows, adhesive strength increased at higher current level.
... These can be implanted into the body and allowed to develop naturally through the process of biological self-bone development to improve the quality of a person's life and longevity. The best choice of biomaterials for a given biomedical application depends on a variety of factors, including mechanical properties, surface morphology, surface chemistry, biodegradability, nontoxicity, and corrosion or wear resistance [70,71]. The biomaterial implant must not alter plasma proteins (including enzymes) in such a way that unfavourable immune responses are elicited. ...
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Surface modifications play a vital role in the performance of bio-implants. Powder mixed electric discharge machining (PM-EDM), a recently developed advanced machining method, can machine and coat the surface of conductive materials at the same time. Hydroxyapatite is a bio-ceramic with a bone-like composition and excellent biocompatibility. Several coating techniques are used to deposit a bio-ceramic layer on the implant surface; however, hydroxyapatite powder mixed-EDM (HAp-EDM) is an electro-thermal process that can be used for surface coating as well as machining of metallic biomaterials. In this review article, surface characteristics such as surface morphology/topography, micro-hardness, phase analysis, recast layer, elemental composition, corrosion/wear resistance, and biocompatibility of the coated surface of an implant after HAp-EDM have been meticulously reviewed. This review also looks at future research opportunities for the HAp-EDM process to meet the high standards required for biomedical materials and their applications in bio-implant manufacturing. ARTICLE HISTORY
... Nanimina et. al. [107]. Experimental results showed that using nano aluminium powder as a matrix in EDM to machine Ti6Al4V workpieces with a copper-tungsten electrode improved SF by reducing micro cracks and crates. ...
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In this study, silicon carbide mixed electrical discharge machining (SCMEDM) process has been developed and later on modelled also using an artificial neural network (ANN) based technique as well as response surface methodology (RSM). Experiments were conducted with Al LM-25/SiC metal matrix composites as per Box Behnken design (BBD). Discharge current, pulse-on-time, servo-voltage, powder concentration, tool material and varying reinforcement levels were considered as machining input parameters. Material removal rate, tool wear rate and surface roughness were taken to be the response parameters. Analysis of variance (ANOVA) method was used to investigate the significant effect of parameters on the response measures. The experimental data was trained using a back-propagation ANN technique. Research shows that the influence of current, pulse length and tool material on the machining characteristics of Al LM-25 MMCs is significant. Surrogated models were also developed for proposed process using RSM. However, the accuracy of ANN models was found to be better than that of RSM models.
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Electric discharge coating (EDC) process is a competitive surface coating technology that alters the desired surface characteristics. EDC process deposits the material on the substrates from the sacrificial electrode by spark erosion process with the potential advantage of depositing any materials. This paper extensively reviews the work carried out in the EDC process and suggests areas of improvement for easy adaptability in industrial applications. Here, the variants of the EDC process, the route map for process parameter selection, the advantage over conventional methods, and coating characterization are discussed. The review sequentially presents the fundamental process, detailed analysis of tool and workpiece materials used, process parameters, and applications. EDC process has continued to be a key solution for many industrial needs, with the critical advantage of enhancing the substrate's serviceability and protecting against corrosion, thermal stress, and other adverse environmental conditions. The scope of the work is discussed in detail, with potential industrial and biomedical applications suggesting avenues for researchers and industrialists.
Chapter
Electric discharge machining (EDM) nowadays a major frequently used non-traditional machining processes for machining electrically conductive materials. It can machine even the hardest of known conductive materials; however, this process lacks on the sustainable scale due to its high power consumption, emission of fumes and other harmful waste materials. An operator may develop respiratory problems and skin related infections due to the harmful gaseous emission, odor and chemical nature of dielectrics. Besides this the non-degradable sludge is also a threat to our environment as it can damage our soil and water. In this paper, dielectrics have been studied and reviewed in terms of their developments and alternate. The authors have studied the problems associated with the conventionally used hydrocarbon dielectrics mainly kerosene; power mixed electric discharge machining (PMEDM), a variant of EDM has been studied to understand the effects of adding abrasive powder particles in the dielectrics and its consequences on the improvement of various response parameters along with the environmental effects. Similar kind of study has been performed by using the water-based liquid dielectrics and the gaseous phase dielectrics. Issues related to sustainability and the development in biodegradable dielectrics have also been discussed. Based on these reviews, some future recommendations have been suggested.
Chapter
Electro-discharge Machining (EDM) advantages are limited by its limitations caused by the process instability. Powder Mixed EDM (PMEDM) is one of the processes which is used to maintain/improve the process stability by providing the space for effective removal of debris from the machining zone. The process improvement mainly depends on the thermophysical properties of the added powders. Therefore, in this work, an attempt is made to study the effect of addition of the conductive and semi-conductive powders with 1:1 proportion, i.e. 1 g/l Graphite (Gr) and 1 g/l Boron Carbide (B4C) together in the dielectric fluid on EDM outputs such as Material Removal Rate (MRR), Surface Roughness (SR), Tool Wear Rate (TWR), and Percentage of Over Cut (OC). These responses are compared with the results obtained by adding 2 g/l powder to the dielectric fluid individually. It was observed that the addition of combination of powders results in moderate MRR, better SR, TWR, and percentage of OC compared to the addition of individual powders. In addition to this, the machined surface features and the possible elemental compositions of the machined surfaces were analysed using FESEM, EDS and XRD.
Chapter
The present work is an extension of the work carried out by the authors previously. In the present study, the optimization of input parameters for wire-EDM cutting of a 2.5 mm thick Ti6Al4V alloy sheet was carried out to have desired cut quality and cutting speed. The experiments were statistically designed using an L8 orthogonal array. Voltage, current, capacitance, duty cycle, frequency, wire tension, and wire feed, were chosen as the input parameters. Kerf width, taper angle, surface roughness, and cutting speed were considered as the outputs. A newly developed, nature-inspired algorithm, called the Mayfly optimization algorithm, was used to minimize the kerf width, taper angle, and surface roughness, along with maximization of cutting speed. The minimum value of current, duty cycle, and frequency were found to be favorable to predict the desired output due to lower spark-energy generation. At the same time, the maximum value of voltage, wire feed, and wire tension were formulated by the algorithm for obtaining desired output. Upon confirmation test using the optimized process parameters, satisfactory experimental results were found for the predicted results within acceptable error.
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Al and V ion release from the Ti-6Al-4 V implants due to the long-term interactions with body fluids can cause diseases such as Alzheimer’s, neuropathy, and osteomalacia. Therefore, it is aimed to increase the bonding and biocompatibility between bone and implant by changing the surface roughness, topography, and chemical composition of Ti-6Al-4 V alloy with different physical, chemical, and mechanical methods. The study proposes to obtain a porous surface coated with Ag-Ca-P on a Ti-6Al-4 V workpiece by the use of sintered silver-hydroxyapatite powder added to electrodes in Electrical Discharge Machining. Micronized silver and hydroxyapatite powders were mixed in different proportions by volume using the powder metallurgy method to achieve the proposed aims. A parametric experimental study was conducted and the surface properties of the treated samples were analyzed by optical microscopy, scanning electron microscopy, energy dispersion spectroscopy, and X-ray diffractometry. The results have confirmed the formation of a porous silver-hydroxyapatite-rich layer on the electrical discharged machined Ti-6Al-4 V surfaces. Therefore, it has been concluded that electrical discharge machining is a promising alternative method for obtaining biocompatible functional surfaces.
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AISI D3 die steel is extensively used in long-run dies for blanking, forming, deep drawing, and thread rolling. Among all the non-traditional machining processes, the Electric Die Sinking Process (EDSP) is mostly employed to manufacture these long-run dies. The EDSP method produces a surface of high quality, which impacts product performance significantly. The surface roughness of AISI D3 die steel is examined in relation to a number of parameters, including peak current, pulse-on duration, gap voltage, and powder concentration. Copper is selected as the tool. Orthogonal array concept coined by Taguchi has been deployed to execute the experiments. It is clearly understood from the results that powder concentration has a key impact on machined surface quality by lessening the generated cracks and enhancing the surface finish by 20%. Further, peak current has more impact on the performance characteristics than pulse-on time and the gap voltage.
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Biodegradable implants are in the focus of recent research approaches in the medical engineering sector for the treatment of many different defects. In comparison to permanent implants the risk of inflammatory reactions is significantly reduced and no foreign material is left in the body using degradable materials. Due to the extraordinary biocompatibility and initial structural stability, similar to the human bone, magnesium alloys are best suited for degradable orthopedic implants. But up until now the degradation of magnesium inside the human body is too fast and therefore the structural stability is lost too early. Newest research suggests that the degradation kinematic as well as the cell response of the implant can be improved by adjusting certain surface properties, e.g. complex micro- and macrostructures. Since these structures are very difficult to be machined with conventional processes, especially for complex and filigree 3D-structures, alternative manufacturing processes need to be developed. Electro Discharge Machining in combination with a Plasma Electrolytic Conversion of the surface is very well suited for the creation of geometries with high aspect ratios and microstructures. The focus of this paper lies on the investigation of the influence of the production processes on the biocompatibility of the machined part. The process chain for such implants will therefore be analyzed in regard to macro and micro surface properties using SEM and EDX-analysis. These results are then compared to biocompatibility testing concerning cell viability and toxicity.
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In the area of materials science, corrosion of biomaterials is of paramount importance as biomaterials are required for the survival of the human beings suffering from acute heart diseases, arthritis, osteoporosis and other joint complications. The present article discusses various issues associated with biological corrosion of different kinds of implants used as cardio stents, orthopedic and dental implants. As the materials used for these implants are manifold starting from metallic materials such as stainless steel (SS), cobalt chromium, titanium and its alloys, bioceramics, composites and polymers are in constant contact with the aggressive body fluid, they often fail and finally fracture due to corrosion. The corrosion behavior of various implants and the role of the surface oxide film and the corrosion products on the failure of implants are discussed. Surface modification of implants, which is considered to be the best solution to combat corrosion and to enhance the life span of the implants and longevity of the human beings is dealt in detail and the recent advances in the coating techniques which make use of the superior properties of nanomaterials that lead to better mechanical properties and improved biocompatibility are also presented.
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Purpose: Research and development of modern medical implants is complex and demanding process focused on fulfilling requirements regarding materials, machining technologies and functionality. Typical example of modern medical implant is elbow nail for fixation of Caput radii fractures. It could be manufactured with classical machining technologies and with advanced Rapid Prototyping technologies such as highly targeted metal deposition technology LENS (Laser Engineered Net Shaping).Design/methodology/approach: Development of modern medical implants is a multi-stage design and manufacturing process primarily based on computer aided design (CAD), computer simulations, machinability of certificated biomaterials, in-vitro biofunctionality and in-vivo tests.Findings: LENS technology enables rapid and agile manufacturing, improved design flexibility, repair and re-manufacture. Material built with LENS technology has equal or even better mechanical and material properties. In medical application LENS technology enables development and rapid prototyping of special surgical instruments, trauma and orthopaedic high-performance implants which are hollow and thin walled.Research limitations/implications: To confirm assumption regarding better material and mechanical properties of products made with LENS technology additional static, dynamic (the High-Cycle-Fatigue test) and material (porosity and microstructure) tests will be carried out in the near future.Practical implications: Three different designs of bone fixation nail prototype made of titanium alloy had been manufactured with conventional machining techniques where some disadvantages due to the technology had been identified. To solve those problems LENS technology had been applied. As fourth design hollow thin walled fixation bone nail prototype made of titanium alloy powder (grain size 45μm) had been manufactured and tested.Originality/value: Paper presents case study where LENS technology is being applied to manufacture modern medical implants. Particular focus of the paper is on material quality and quality benefits obtained in current and future medical application.
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Electrical discharge machining (EDM) is one of the important non-traditional machining processes and it is widely accepted as a standard machining process in the manufacture of forming tools to produce molds and dies. Since its introduction to manufacturing industry in late 1940s, EDM became a well-known machining method. The method is based on removing material from a workpiece by means of a series of repeated electrical discharges, produced by electric pulse generators at short intervals, between an electrode (tool) and a part being machined in dielectric fluid medium. This paper is devoted to a study of the influences of EDM parameters on surface roughness for machining of 40CrMnNiMo864 tool steel (AISI P20) which is widely used in the production of plastic mold and die. The selected EDM parameters were pulsed current (8, 16 and 24 A), pulse time (2, 3, 4, 6, 12, 24, 48 and 100 μs) and pulse pause time (2 and 3 μs). It was observed that surface roughness of workpiece and electrode were influenced by pulsed current and pulse time, higher values of these parameters increased surface roughness. Lower current, lower pulse time and relatively higher pulse pause time produced a better surface finish.
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This paper presents the effects of various powder characteristics on the efficiency of electrodischarge machining (EDM) SKD-11. The additives examined include aluminium (Al), chromium (Cr), copper (Cu), and silicon carbide (SiC) powders that have significant differences in their thermophysical properties. The machining mechanism with the addition of the foreign particles, the tool wear rate (TWR), and the material removal rate (MRR) have been investigated. It was found experimentally that the particle concentration, the particle size, the particle density, the electrical resistivity, and the thermal conductivity of powders were important characteristics that significantly affected the machining performance in the EDM process. Proper addition of powders to the dielectric fluid increased the MRR and, thus, decreased the TWR. Under the same particle concentration experiments, the smallest suspended particle size led to the greatest MRR and, thus, the lowest TWR. Of the additives investigated, chromium powder produced the greatest MRR and the lowest TWR, whereas the process without foreign particles has the converse effects. The addition of copper powder to the dielectric fluid was found to make almost no difference to the pure kerosene EDM system.
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This investigation elucidates the biocompatibility and microstructural variation of Fe–Al–Mn and electro-discharged Fe–Al–Mn alloys. A recast layer was formed on the alloy surface, following electro-discharged machining. γ-Phase and Fe0.6Mn5.4C2 carbide (κ-carbide) were formed on the recast layer following electro-discharging. The γ-phase and κ-carbide are nanostructures. The nano-(γ-phase + κ-carbide) has important roles in forming nanostructured oxide layer. Furthermore, electro-discharging not only generates a nanostructural recast layer, but also converts the alloy surface into a nanostructured oxide surface, increasing the alloy biocompatibility.
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This study investigated the properties of Ti-6Al-4V alloy after surface treatment by the electric discharge machining (EDM) process. The EDM process with high peak currents proved to induce surface macro-roughness and to cause chemical changes to the surface. Evaluations were made of the mechanical properties by means of tensile tests, and of surface roughness for different peak currents of the EDM process. The EDM process with peak current of 29 A was found to induce sufficient surface roughness, and to have a low adverse effect on tensile properties. The chemical changes were studied by scanning electron microscopy equipped with an energy dispersive X-ray analyser (EDX). The surface of the benchmark samples was obtained by plasma-spraying a titanium dioxide coating. An investigation of the biocompatibility of the surface-treated Ti-6Al-4V samples in cultures of human osteoblast-like MG 63 cells revealed that the samples modified by EDM provided better substrates for the adhesion, growth and viability of MG 63 cells than the TiO2 coated surface. Thus, EDM treatment can be considered as a promising surface modification to orthopaedic implants, in which good integration with the surrounding bone tissue is required.
Article
Three different microstructures--equiaxed, bi-modal and coarse lamellar--are prepared from Ti-6Al-4V alloy. Electric discharge machining (EDM) with a high peak current (29 A) is performed in order to impose surface roughness and modify the chemical composition of the surface. Detailed scanning electron microscopy (SEM) investigation revealed a martensitic surface layer and subsurface heat affected zone (HAZ). EDX measurements showed carbon enriched remnants of the EDM process on the material surface. Rotating bending fatigue tests are undertaken for EDM processed samples for all three microstructures and also for electropolished-benchmark-samples. The fatigue performance is found to be rather poor and not particularly dependent on microstructure. The bi-modal microstructure shows a slightly superior high cycle fatigue performance. This performance can be further improved by a suitable heat treatment to an endurance limit of 200 MPa.