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Wear characteristics of FeW/FeW-B4C coatings produced by TIG process
Abstract
In this study, wear properties of FeW-B 4 C coatings produced by tungsten inert gas (TIG) process on the AISI 1060 steel were investigated. TIG process was selected because it is a cost-effective approach for melting-based coatings. The treated surfaces were evaluated and characterized by means of scanning electron microscope (SEM), X-ray diffraction analysis, and electron dispersive spectrometry (EDS). The microhardness and wear experiment were also performed by using a microhardness machine and ball-on-disk tribometer. SEM observations showed that the obtained coating had a smooth and uniform surface. According to XRD analysis, borides and carbides phases formed in the coatings. The wear behavior of the coatings was compared with ball-on-disc configuration wear tests, at the same conditions. Average coefficient of friction values of the coatings were obtained at relatively low levels.
In this work, the surface of AISI 430 stainless steel was coated with a hyper-eutectic FeCrC and pure B 4 C powders using the plasma transferred arc (PTA) welding method. Further, the microstructure, microhardness, and abrasive wear resistance of the coated layer were evaluated in this work. Hard coating layers were formed between 750[Formula: see text]HV and 1000[Formula: see text]HV from the PTA melting coating process with high energy input (due to PTA). Due to the addition of FeCrC and B 4 C, the martensite, austenite, M 7 (C-B) 3 , M[Formula: see text](C-B) 6 , Cr(C-B), FeCr, Fe 2 B, Fe 3 C, Fe 2 C, SiC, and Fe 3 (C-B) phases were formed in the coating layer which makes the layer very hard. The abrasive wear resistance of the coated layer was evaluated using the Taguchi method with L[Formula: see text] mixed-level orthogonal index. Samples, wear distance (m), applied load (N), and abrasive grain size (grid) were chosen as input parameters. The mass loss due to wearing was evaluated based on “the smaller the better”. All input parameters significantly influence the wear, but the highest effect was found with the wear (slip) distance. Also, a linear regression equation was obtained to estimate the mass loss between the parameters and the levels used.
Friction stir processing has evolved as a novel method to fabricate surface metal matrix composites. The feasibility to make B 4 C particulate reinforced copper surface matrix composite is detailed in this paper. The B 4 C powders were compacted into a groove of width 0.5 mm and depth 5 mm on a 9.5 mm thick copper plate. A tool made of high carbon high chromium steel; oil hardened to 63 HRC, having cylindrical profile was used in this study. A single pass friction stir processing was carried out using a tool rotational speed of 1500 rpm, processing speed of 40 mm/min and axial force of 10 kN. A defect free interface between the matrix and the composite layer was achieved. The optical and scanning electron micrographs revealed a homogeneous distribution of B 4 C particles which were well bonded with the matrix. The hardness of the friction stir processed zone increased by 26% higher to that of the matrix material.
The purpose of this work was to investigate the coatings made of Cr3 C2 and SiC powder manufactured on AISI 304 stainless steel applied by the plasma transferred arc (PTA) welding process. SiC content in the produced coated layer was varied between 0–100 wt.% and the effect of SiC concentration on the microstructure and hardness of the coating was measured experimentally. SEM analyses revealed that the composite coatings had a homogeneous, nonporous, and crack-free microstructure. Dendrites and interdendrite eutectics formed on the coating layer, subject to the temperature gradient and the solidification ratio. There was a significant increase in the hardness of coating layers with the effect of the γ -(Fe,Ni), Cr7 C3, Cr23 C6, Fe5 C2, Cr3 Si, CrSi2, Fe>0.64 Ni0.36, CFe15.1, C-(Fe,Cr)-Si phases formed in the microstructure. In comparison to the substrate, the microhardness of the coatings produced by PTA were 2.5–3.5 times harder.
Tungsten inert gas (TIG) welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on substrates. Surface melting was conducted by TIG welding to produce Al-SiC layer on the surface. Microstructural evolution was investigated by X-ray diffractometry (XRD), optical and scanning electron microscopy (SEM) and elemental microanalysis (EDS). Properties of clad layers were studied by microhardness and sliding wear testing. The results showed a uniform distribution of SiC particles in dendritic aluminum matrix. Addition of excess silicon caused the formation of eutectic crystals and coarse silicon particles in the clad layer which resulted in higher hardness and wear resistance of clad layers.
The Ni60A and Ni60A/SiC coatings were obtained by laser cladding on 0.45% C steel. The microstructure and hardness of the coatings were studied by SEM and XRD. The erosion resistances of Ni60A and Ni60A/SiC coatings were also investigated. The results show that the structure of different coatings is up to the temperature gradient and solidifying velocity in metal-melting region during laser cladding process. The coatings consist of a cladding layer, in which dendritic crystal and bulky cell-like crystal exist mainly, and a thermo-affected layer. Ni60A/SiC coating has higher microhardness than that of Ni60A coating, which is mainly caused by SiC and complicated phases formed by Ni, Cr, Fe, C and Si. It is obvious from the erosion test that the Ni60A/SiC coating has high erosion resistance.
To enhance the wear resistance of mechanical components, laser cladding has been applied to deposit in situ TiB2/Fe composite coating on steel using ferrotitanium and ferroboron as the coating precursor. The phase constituents and microstructure of the composite coating were investigated using X-ray diffraction (XRD), scanning electron micrograph (SEM) and electron probe microanalysis (EPMA). Microhardness tester and block-on-ring wear tester were employed to measure the microhardness and dry-sliding wear resistance of the composite coating. Results show that defect-free composite coating with metallurgical joint to the steel substrate can be obtained. Phases presented in the coating consist of TiB2 and α-Fe. TiB2 particles which are formed in situ via nucleation-growth mechanism are distributed uniformly in the α-Fe matrix with blocky morphology. The microhardness and wear properties of the composite coating improved significantly in comparison to the as-received steel substrate due to the presence of the hard reinforcement TiB2.
The metallurgical behavior of B4C in the iron-based surfacing alloy during plasma transferred-arc (PTA) Fe–B4C composite powder surfacing was investigated and discussed in this paper. Based on the experiment results it is found that Fe–B4C composite coatings can only be prepared by PTA powder surfacing in the case that the employed surfacing current is little enough. The metallurgical reactions between Fe and B4C are limited in a very narrow region at their contacting interface in this case. With the increasing of employed surfacing current more and more B4C particles will be fully melted and reacted with the liquid iron-based alloys. However, the products of the metallurgical reactions between them are various for the different powder compositions and surfacing conditions. Most of the B4C particles will be fully melted during the PTA powder surfacing while 200A or greater surfacing current is used. Furthermore, most of the C element in B4C particles is tending to be graphite rather than reacting with Fe to be carbides during the processing under the Fe–B4C composite powder PTA surfacing conditions.
Laser surface alloying of Mo, WC and Mo–WC powders on the surface of Ti6Al4V alloys using a 2 kW Nd-YAG laser was performed. The dilution effect upon the microstructure, microhardness and wear resistance of the surface metal matrix composite (MMC) coating was investigated. With a constant thickness of pre-placed powder, the dilution levels of the alloyed layers were found to increase with the incident laser power. The fabricated surface MMC layer was metallurgically bonded to the Ti6Al4V substrate. The microhardness of the fabricated surface layer was found to be inversely proportional to the dilution level. The EDAX and XRD spectra results show that new intermetallic compounds and alloy phases were formed in the MMC layer. With the existence of Mo content in the pre-placed powder, the β-phase of Ti in the MMC coating can be retained at the quenching process. With increasing weight percentage content of WC particles in the Mo–WC pre-pasted powder, the microhardness and sliding wear resistance of the laser surface coating were increased by 87% and 150 times, respectively, as compared with the Ti6Al4V alloy. The surface friction of the laser-fabricated MMC coatings was also decreased as compared with the worn Ti6Al4V substrate.
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Fig. 10. SEM image and EDS data of worn surface of FeW-10 B 4 C coating
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