Robert Bidulský

• Professor at Polytechnic University of Turin

This review describes the process of metal additive manufacturing and focuses on the possibility of correlated input parameters that are important for this process. The correlation of individual parameters in the metal additive manufacturing process is considered using simulation tools that allow the prediction of various defects, thus making the r...

The main goal of this contribution is to evaluate the mechanical properties, strengthening contributions and microstructure development of austenitic stainless steel AISI 316 LN with high nitrogen content in the states characterized as the initial state and the states after rolling with different thickness deformations. The initial state was repres...

The L-PBF process belongs to the most modern methods of manufacturing complex-shaped parts. It is used especially in the automotive, aviation industries, and in the consumer products industry as well. Numerical simulation in the powder sintering process is a means of optimizing time efficiency, accuracy and predicting future errors. It is one of th...

Vedecká monografia predstavuje súhrnné poznatky o technológií práškovej metalurgie (PM) v oblasti kovových práškov. Vyzdvihuje výnimočnosť tejto technológie a prednosti, ktoré umožnili PM zaujať popredné miesto v oblasti výroby súčastí a súčiastok pre široké spektrum koncových užívateľov.

Formability and its prediction of high-strength steels is an important research subject for forming specialists and researchers in this field. Springback and its accurate prediction of high-strength steels are very common issues in metal forming processes. In this article, the impact of blank holding force and friction on the parts springback made...

The aim of the article is to examine the workability of sintered powder material of aluminum alloy (Alumix 321) through severe plastic deformations under the conditions of the equal channel angular rolling (ECAR) process. Accordingly, the stress–strain analysis of the ECAR was carried out through a computer simulation using the finite element metho...

Additive manufacturing is recognized as a potential technology to design and create complex geometries as well as a fast track to build prototype components. Different materials are possible to use, depending on the specific requirements of an application. Superconducting applications like magnets or rotating machines are demanding for the structur...

To design a reliable forming process it is necessary to determine the mechanical and formability properties of the processed material, which are used as input parameters for forming simulations. High-strength steel is irreplaceable as a material for producing the deformation zones of current automobiles. This type of steel can be processed by conve...

In this work, AA1070 aluminium alloy sheets are joined using TIG and MIG welding after three different edge preparations. Shearing, water jet and plasma-cut processes were used to cut sheets, subsequently welded using ER5356 and ER4043 filler metals for TIG and MIG, respectively. Mechanical properties of the obtained sheets were assessed through te...

In the last years, functionalized powders are becoming of increasing interest in additive manufacturing (particularly in laser powder bed fusion processing, L-PBF), due to their improved flowability and enhanced processability, particularly in terms of laser absorbance. Functionalized powders may also provide higher final mechanical or physical pro...

During the past 50 years, the aim to reduce the eddy current losses in magnetic cores to a minimum led to the formulation of new materials starting from electrically insulated iron powders, today called Soft Magnetic Composites (SMC). Nowadays, this promising branch of materials is still held back by the mandatory tradeoff between energetic, electr...

In recent years, innovative magnetic materials have been introduced in the field of electrical machines. In the ambit of soft magnetic materials, laminated steels guarantee good robustness and high magnetic performance but, in some high-frequency applications, can be replaced by Soft Magnetic Composite (SMC) materials. SMC materials allow us to red...

In this study, the efficacy of an innovative ultra-fast sintering technique called electro-sinter-forging (ESF) was evaluated in the densification of Fe-Cr-C steel. Although ESF proved to be effective in densifying several different metallic materials and composites, it has not yet been applied to powder metallurgy Fe-Cr-C steels. Pre-alloyed Astal...

This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UH...

The main idea of the co-organize the Slovak space tech day and Slovak aviation industry days was to prove the position of Košice self-governing region (KSK), as a space in which suitable conditions are created for development in the areas of the space industry and aviation. The basis is a long-term historical context in the form of educational and...

In this study one of the most innovative sintering techniques up to date was evaluated: Electro-Sinter-Forging (ESF). Despite it has been proved to be effective in densifying several different metallic materials and composites, bearing steels such as 100Cr6 have never been processed so far. Pre-alloyed Astaloy CrM powders have been ad-mixed with ei...

Additive manufacturing is a key enabling technology in the manufacture of highly complex shapes, having very few geometric limitations compared to traditional manufacturing processes. The present paper aims at investigating mechanical properties at cryogenic temperatures for a 316L austenitic stainless steel, due to the wide possible cryogenic appl...

The main aim of the present paper is evaluated the mechanical properties, microstructures and porosity of Ti6Al4V and CoCrW alloys produced by Laser Powder Bed Fusion (L-PBF) as an additive manufacturing (AM) technology. The mechanical properties were follows: For Ti6Al4V alloy the UTS was 1180 MPa; the YS was in the range <600; 745 MPa>. For CoCrW...

The influence of rolling temperatures performed at ambient and cryogenic conditions in the interval of deformations ε = <10; 50> (%) on structural development and mechanical properties of steel grade AISI 316LN was studied. The evaluations of microstructures were studied by optical and transmission electron microscopy. The initial strength properti...

p class="AMSmaintext">The goal of the present work is to evaluate mechanical properties and to analyse the microstructure of 316L stainless steel produced by Laser Powder Bed Fusion (L-PBF) follow by rolling with different thickness reduction under ambient and cryogenic conditions. The samples before rolling were heat treated. The static tensile te...

In powder metallurgy (PM), severe plastic deformation (SPD) is a well-known technological solution to achieve interesting properties. However, the occurrence of pores in the final product may limit these properties. Also, for a given type of microstructure, the stereometric parameters of the pore structures, such as shape (represented by Aspect and...

Aluminum alloys are widely used to produce automotive components, thanks to their great mechanical properties–to–density ratio. Engine components such as pistons are conventionally produced by casting of Al–Si eutectic alloys (Silumin alloys) such as EN AC 48000. Due to the harsh working conditions and the lower ductility if compared to aluminum–si...

This work deals with comparing the mechanical properties of OFHC copper and CuCrZr alloys processed by asymmetric ambient rolling (ASaR) and asymmetric cryorolling (AScR). The conditions for asymmetrical rolling were ensured by different diameters of the main rolls. The thickness of samples was reduced about 20% - 70% at ambient temperature and at...

Electrical machines cover a very wide range of applications in many industrials sectors and the research to improve the performance of those applications is recently leading to the development of new solutions. Those devices are generally equipped with magnetic circuits made of laminated ferromagnetic steel, but in the last decade, new magnetic mat...

p class="AMStitle"> The interest around the adoption of Soft Magnetic Composite materials (SMC) in the realization of electric machines, or parts of electric machines, is continuously increasing. The main reason lies on the opportunity to realize magnetic circuits following a 3D design procedure, which is not allowed with the adoption of the tradit...

p class="AMSmaintext">The aim of this study is to analyze and to summarize the results of the processing of aluminum alloys, and in particular of the Al-Si-Mg alloys, by means of the Additive Manufacturing (AM) technique defined as Laser Powder Bed Fusion (L-PBF). This process is gaining interest worldwide thanks to the possibility of obtaining a f...

Derivation, validity testing and usage in practice of the powder compaction Eq. P = P0.exp(− K.pⁿ) is presented. P is the porosity at pressure p, P0 the porosity at p = 0, parameters K and n represent the synergistically acting compaction parameters. The relationship between K and n, ln(K) = 1.2952–7.3349.n or K = 3.6517.exp(− 7.3349.n), was found...

p class="AMSmaintitle"> Ultrafine grained materials are capable of superplastic elongation at strain rates faster than those currently employed for commercial superplastic forming operations. However, such operations require the material in the form of thin sheets. Asymmetric rolling (ASR), as one of severe plastic deformation (SPD) methods, was us...

The present paper deals with a study on formation of specific substructural features in OFHC copper processed by equal-channel angular pressing (ECAP) considering different strain rate conditions. Since two mechanical tensile testing equipments were being used, strain rate response could be studied in a wide range (both in static and dynamic regime...

This article deals with the analysis of formability of heat resistant steel type 9Cr-1Mo by physical laboratory simulation - hot compression test. The 9Cr-1Mo steel belongs to modern 9% Cr tempered martensitic steel for high-temperature applications in advanced thermal power plants. The shape of the sample was defined based on numerical simulations...

The goal of the present work is to compare progressive technology — rolling at cryogenic temperature and classical rolling at ambient temperature followed by an investigation of their impact on the final microstructure and the magnetic properties of non-oriented electrical steel. Non-oriented electrical steel is characterized by high magnetic induc...

Wear (pin-on-disk) tests of low-alloy powder steels (with 0.5 and 0.65% C) are performed after vacuum sintering combined with hardening. The studied alloying systems are 0.65% C + 1.5% Cr + 0.2% Mo, 0.65% C + 0.9% Ni + 0.9% Mo + 0.2% Mn and 0.5% C + 4% Ni + 1.5% Cu + 0.5% Mo. The wear resistance of the steels after the hardening sintering is an ord...

The specimens manufactured using principle LS (Laser sintering) by the additive manufacturing technologies from the Ti-6Al-4V (Grade 5) titanium alloy are investigated. The powder Ti-6Al-4V is well-known for its slightness and high strength. Metal additive manufacturing processes produce parts with porosity. The possibility of changes in a porosity...

This study is focused on the evaluation of mechanical properties and microstructure of fabricating Ni-free CoCrW-alloy. Samples were prepared by additive manufacturing technology–selective laser melting. The chemical composition of used metal powder was–60.5% Co, 28% Cr and 9%W. Parameters of SLM were given by powder supplier. The shape of thesampl...

This paper is focused on the evaluation of formability of heat resistant steel type 9Cr-1Mo by laboratory numerical simulation – hot compression test confirmed by laboratory hot compression test. The 9Cr-1Mosteel represents modern 9%Cr tempered martensitic steel for high temperature applications in advanced thermal power plants. Numerical simulatio...

This study reports on an investigation of factors affect the process of compacting Al chips which are used to direct scrap processing through the forward extrusion method. EN AW 6060 chips of different geometry and types were mainly used as the experimental material. The chips were compacted in a die with a vertical channel (10.3mm in diameter). To...

Goal of the present paper is the analysis of the interparticle neck connections in a system made of insulated iron powder compounds with dierent additions of an AlMgSiCu alloy (0.25, 0.5 and 0.75 wt%). The introduction of the aluminium alloy powder has been made in order to improve the mechanical properties, evaluated as the transverse rupture stre...

The contribution deals with dry sliding wear behaviour of different Fe–Cr–Mo–[Mn]–[Cu] sintered powder metallurgy systems using a pin on disc test. The effect of chemical composition and two different processing conditions, industrial atmosphere at 1453 K (1180°C) and vacuum atmosphere at 1513 K (1240°C) related to a new proposed type of sinterhard...

In this paper is evaluated workability of rolled aluminium alloy based AIMgSi. Static tension test was used for obtained the mechanical properties, such as tensile strength, yield strength, elongation, the strain hardening exponent and coefficient of surface anisotropy. Rolled samples used for a tensile test were taken in three different directions...

The experimental and theoretical investigation deals with laser welding of automotive thin steel sheets. As tested materials were used Interstitial Free Steel (IF) from type of Hight Strength Low Alloy (HSLA) and the second is S420 steel (Micro-Alloyed Steel). Weld quality has been measured with the help of microhardness test and microstructure. Ch...

A die setup for direct hot extrusion of extra-short aluminium alloys billets used in semi-pilot plant tests was simulated using DEFORM ™ 2D/3D software and results were compared with experiment. A die setup without welding chamber proved to shorten charge-weld to such extend that most of material could be recovered as usable samples. Having good ag...

In this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was sub...

The present paper is focused on the effect of manganese on microstructure development of admixed Fe-Mn-C sintered steels along with diffusion characteristics of manganese in the iron matrix. Admixed systems were prepared on the base of sponge iron powder, with addition of 0.3% C and 3% Mn added as ferromanganese. Sintering at 1,023, 1,173, 1,323, 1...

The production of electrical energy from nuclear fusions is currently highly advanced field of the interest in an international scientific cooperation in the International Thermonuclear Experimental Reactor programme (ITER). Alloys based on Cu are used in the ITER project however from the future perspective in terms of the physical and mechanical p...

The present paper focused on the effects of aluminium alloy addition on the behaviour of soft magnetic materials at low frequencies. The microstructure investigation reveals that for materials with high aluminium contents, the pores are oriented near or surrounding the aluminium particles. The microstructure investigation reveals that for materials...

This article deals with the analysis and comparison of the conditions for solid state welding during extrusions by means of numerical simulation. Numerical simulations made on four different matrices, such as square die without integrated extrusion and equal channel angular pressing (iECAP), porthole die whit one and four square profile. Maximum vo...

Goal of the present paper is the analysis of the fracture surfaces of an Insulated Iron Powder Compound (IIPC) with different additions of aluminium alloy (0.25, 0.5 and 0.75 wt.%), in order to improve the mechanical properties, evaluated as the transverse rupture strength (TRS) with sufficient magnetic properties (mainly represented by the iron lo...

Non grain oriented isotropic electrical steels, commercially called NGOES, were investigated in cryogenic temperature conditions. At cryogenic temperatures plastic deformations form strong structural heterogeneities in the sample thickness. Samples processed by cryo rolling show a bigger storage energy. To achieve abnormal grain growth through the...

The present paper deals with the sliding wear behaviour of prealloyed chromium sintered steel (Fe-1.5Cr-0.2Mo) with graphite powder added in the amount of 0.7%. The wear characteristics, such as profilograms, wear tracks morphology and wear curves of the as sintered specimens and TiCN coating were investigated through pin-on-disk tests. The specime...

The main aim of this paper is to investigate the effects of different processing conditions on the behavior of a P/M (Powder Metallurgy) aluminum alloy with respect to the microstructure, fracture and mechanical properties. Moreover, the evolution of porosity as a consequence of pressing, sintering and ECAPing processes was investigated. A commerci...

The influence of thermo-plastic processes through methods of severe plastic deformations (SPD) and rolling carried out at ambient and cryogenic temperatures on recovery of two materials was investigated. The aim of this study was to insert strains to materials having middle and high stacking fault energy (SFE) in ambient and cryogenic temperature c...

The paper is focused on the role of the pressing pressure on the densification behaviour of PM aluminium alloys. Commercially aluminium based powders Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn were used as materials to be investigated. The apparent density of the powder mixes was determined according to MPIF St. 04. A set of cylinder test specimen 55 x 10 x...

The paper focuses on the effect of both the aluminium alloy addition and microstructural inhomogeneties on the magnetic behaviour of soft magnetic materials tested at low frequencies. The IIPC material (base on the commercial Somaloy 1P powder) has been blended with different amounts of commercially aluminium alloy Alumix 321 (0, 5 and 10 wt %). Sp...

The aluminium alloy with chemical conception AlMgSi prepared by PM (powder metallurgy) technology was used. The experiments such as a ring and compression test, ECAR (equal channel angular rolling) for determination of friction coefficient, stress-strain curves and material workability based on analytical methods (Freudenthal, Cockcroft-Latham and...

The main aim of this paper is to investigate, by means of comparison of experimental studies and mathematical models, the evolution of porosity as consequence of pressing, sintering and ECAPping an aluminium based powder (6xxx). After applying the compacting pressure, specimens were dewaxed in a ventilated furnace at 400 degrees C for 60 min. Sinte...

The present paper deals with the evaluation of different vacuum heat treatments on the fracture surfaces of a low alloyed sintered steel in correlation with the mechanical and plastic properties achieved. The heat treatment conditions consist of the sintering process in vacuum furnace at 1393 K for 1800 s with an integrated final tempering at 473 K...

The main aim of this paper is to investigate the evolution of porosity as consequence of pressing, sintering and ECAPping an aluminium based powder, by means of comparison of calculated and experimental results. After applying compacting pressure, specimens were dewaxed in a ventilated furnace at 400 °C for 60 min. Sintering was carried out in a va...

The main aim of the paper are analysis the effect of the processing conditions on the magnetic behaviour of iron insulated powder compound (IIPC) materials admixed by aluminium alloy at low frequencies. Results show that the higher applied compactive pressures cause a greater reduction of volumes and of present porosities. The behaviour of powders...

The main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (Al-Mg-Si-Cu-Fe) was used as investigated material. After applying different pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventil...

The present paper deals with the evaluation of the effect of different vacuum heat treatments on the microstructure and fracture surfaces of a low alloyed sintered Fe-[1.5Cr-0.2Mo]-0.6C steel, in correlation with the mechanical and plastic properties achieved. The heat treatment consists of the sintering process in vacuum furnace at 1393 K for 1800...

The mechanical properties and substructure formation of high purity aluminium (99.999%) processed by severe plastic deformation method (equal channel angular pressing) were studied. The equal channel angular pressing process was carried out at room temperature by route C (sample rotation around the axis about 180 ° after each pass) in a die with tw...

The main aim of this paper is the analysis of the effects of various processing conditions on the magnetic, mechanical, and energetic properties of mixture systems consisting of insulated iron powder compound and aluminum alloy. Specimens with a different green density (obtained with compacting pressures of 400, 600, and 800 MPa) were treated in di...

The present paper deals with the tribological behaviour of the boride and carbide hardmetals evaluated by performing comparative dry sliding pin-on-disc experiments using normal contact loads. Analyses of the wear performance results, microstructural evaluation and processing conditions effect indicate that microstructure inhomogenities play an imp...

The main aim of this paper is to show how porosity evolves, in terms of morphology and distribution, considering that pores represent potential fracture initiation sites under applied loads. An aluminium based powder (Al-Mg-Si-Cu-Fe) was used as material to be investigated. After applying different compacting pressures (400 and 600 MPa), specimens...

R. Bidulsky(a), J. Bidulska(b) and M. Actis Grande(a) ((a)Politecnico di Torino, Department of Applied Science and Technology, Alessandria, Italy, (TU)-T-b of Kosice, Faculty of Metallurgy, Dpt. of Metals Forming, Slovakia): Geometrical and Microhardness Aspects of Aluminium PM Alloys as Function of Local Plastic Deformation The paper deals with th...

The main aim of this work is to evaluate the possible application of powder metallurgy (PM) for the production of armour elements. Different materials were used, as starting base, consisting of pre-alloyed powders and powder mixtures with alloying elements like Mn, Mo, Cr, Ni and C. Disc (ASTM G 99) specimens were compacted by applying a pressure o...

The main preparation way of PM aluminium alloys are presently conventional press-and-sintering methods. The first stage of rigid die compaction is a basic forming technique used in the production of a lot of PM materials. It is primarily uniaxial compaction and the forming operation employs either a mechanical or a hydraulic press. A classical way...

The high-temperature behaviour of aluminium alloy EN AW 2014 was investigated in a wide range of deformation temperatures and strain rates. The influence of strain rate and temperature on the peak stress was analysed using the conventional constitutive equation (relating strain rate, flow stress, and temperature) and by means of precise definition...

The present paper deals with the evaluation of different vacuum heat treatments on the microstructure of a low alloyed sintered Fe-[1.5 Cr-0.2 Mo]-0.6 C steel. Different gas pressures were applied on the material during cooling from the sintering temperature. The average cooling rates were calculated in the range of 1453K to 673K and were varying f...

The main aim of the paper is to evaluate the influence of high temperature sintering and of cooling rates on the wear resistance of Fe (Cr-Mo) - [0-2% Cu] - 0.65% C systems. The wear behaviour of the sintered steels was investigated through pin-on-disk tests. Two different processing conditions were used, involving different cooling rates from the...

The paper deals with the influence of processing conditions on tensile properties, hardness and structure development of the aluminium alloy EN AW 2014, depending on various processing conditions (as-rolling, quenching, severe plastic deformation - SPD by equal channel angular pressing - ECAP and ageing). The evaluated tensile properties showed tha...

The prediction of evaluation a U-and V-shaped cracks on the surface and subsurface of a continuously cast steel slab, is investigated during hot rolling. The numerical simulation is carried out by means of FE-code DEFORM 3D. Therefore, an algorithmic decision tree was developed by the C 4.5 program and applied in prediction of surface and subsurfac...

The paper focused on the effect of high-temperature sintering along with the back pressure equal channel angular pressing (ECAP-BP) on the porosity distribution in powder metallurgy (PM) aluminium alloys. Analyses of the dimensional and morphological parameters indicate that high-temperature sintering couples to ECAP-BP lead to porosity reduction a...

The high-temperature deformation of EN AW 2014 stabilized by zirconium was investigated in a wide range of deformation temperatures and strain rates. The influence of strain rate and temperature on the peak stress was analysed using the conventional constitutive equation (relating strain rate, flow stress, and temperature) and by means of precise d...

The paper is focused on the wear mechanism of a chromium pre-alloyed Fe (Cr - Mo) - C sintered steel. The wear behaviour of the sintered steel is investigated through pin-on-disk tests. Two different processing conditions have been used, involving a slow cooling rate of 0.05 K/s and a process called sinter hardening with an average cooling rate of...

The paper deals with the influence of severe plastic deformation on the typical powder metallurgy (PM) microstructural characteristics, such as porosity, of a PM aluminum alloy. A commercial ready-to-press aluminum based powder was used as material to be investigated. After applying different compacting pressures (400, 500, 600 and 700 MPa), specim...

The effect of high temperature sintering and high cooling rate on shifting the microstructural composition to the favourably of martensite-bainite structures and thus effective improvement of mechanical properties of sintered steels based on Astaloy CrL powder with an addition of 1 and 2% Cu or 50% Distaloy AB powder and 0.65% C was investigated. A...

The aim of the presented paper is to describe the sintered duplex stainless steels manufactured in sinter-hardening process and their structural and mechanical properties. Duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed base powders by controlled addition of alloying elements...