Key Engineering Materials Vol. 604

Abstract: The aim of the current study was to elaborate and compare abrasive wear resistance of thick metal matrix based deposited coatings. To produce metal matrix composite (MMC) coatings, experimental powders made by mixing commercial nickel and iron based powders with recycled hardmetal powder were used. The usage of recycled hardmetal as an initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Based on structural studies the optimal content of 40 vol% hard phase was selected. Plasma transferred arc (PTA) hardfacing and high velocity oxyfuel (HVOF) spraying were used as deposition technologies. The behavior of coatings by abrasive rubber wheel wear (ARWW ) (based on G 65 standard), abrasive impact wear (AIW) and abrasive erosion wear (AEW) (based on GOST standard) was investigated. The results showed that the wear resistance of experimental PTA hardfacings at high angle impact wear conditions is notably higher than of HVOF sprayed coatings.

Abstract: The investigated brush-plated silver and gold coatings are used for refining the surface properties of electric apparatuses. Tensile residual stresses generated in the plated coatings were determined with a thin-walled ring substrate using the curvature and instrumented indentation techniques. These stresses relax over time; the dependence of relaxation time was approximated by a linear-fractional function. The modulus of elasticity and the nanohardness of the coatings were determined by nanoindentation. The surface morphology and structure in cross-section of the coated substrates are presented.

Abstract: Present study focuses on investigating the hot dip galvanizing effect on the mechanical properties of high strength steel. The effect of chemical pre-treatment (hydrogen diffusion) and the effect of hot dip galvanizing temperature on mechanical properties was studied with high strength steel S650MC. Additional tests were made with widely used structural steel S355J2. A batch type hot dip galvanizing process was used and zinc bath temperature was 450 °C and 550 °C. Results of the study show the behaviour of high strength steel during hot dip galvanizing process.

Abstract: The main goal of this work is to study dry sliding wear behavior of NiCrSiB-TiB₂ plasma sprayed coating against NiCrSiB coating. NiCrSiB-based powders with 10, 20, 40 wt.% TiB₂ particles content were deposited on steel substrates by plasma spraying. The structure of NiCrSiB-TiB₂ coatings consists of Ni-based matrix and TiB₂ and CrB grains. Among the coatings studied, the NiCrSiB-20wt.%TiB₂ shows excellent wear-resistance. The worn surfaces were observed using scanning electron microscopy and Auger electron spectroscopy to determine the wear mechanisms.

Abstract: In this study the influence of the TiB₂, ZrB₂, and CrB₂ additives into NiAl-intermetallics on their wear behavior under friction conditions at the high temperature in the pair with steel has been investigated. It was shown, that the borides additives have influenced on the wear mechanism, significantly increasing the wear resistance of composite coatings pointed out. Among the coatings studied the NiAl-15 wt. % CrB₂ coating showed the best result.

Abstract: Laser texturing of the surface layer of materials is a modern technology with its significant prospects for production of engineering machinery. Produced with this technology oil micro-containers have a major impact on the tribological cooperation improving. The article presents methodology and results of laser texturing of surface layer of alloy steel 40NiCrMo6. The material is usually applied for foot rod of combustion engines production. Application of the laser ablation micro treatment on the side surfaces the foot of the rod allowed to fabricate desired texture in the surface layer, made of hemi-spherical and oil micro-containers.

Abstract: In the present article, the laser hardening of the carbon steel C45, previously coated by the physical vapour deposition (PVD) process, is studied. The (Al,Ti)N-G and nACo® (nc-Al_xTi_1-xN/α-Si₃N₄) coatings were applied. Nd:YAG laser with the laser beam power density of 1945 W/cm² and scan speed of 300 mm/min was used for hardening process. Laser hardening lead to the formation of hardened layer under both coatings, consisting of austenite and ferrite. The approximate depth of the hardened layer and maximal microhardness was approximately 0.2 mm and 955 HV0.05 and 0.1 mm and 520 HV0.05 in the case of the (Al,Ti)N-G and the nACo® coating, respectively. After laser hardening the sliding wear of the (Al,Ti)N-G coating decreased by 1.25 times and of the nACo® coating by 1.05 times.

Abstract: This paper presents analysis of the influence of the laser hardening bearing 100CrMnSi6-4 steel on the selected properties: hardness and microstructure. The best process parameters were selected by: radiation impulse length λ = 1064 nm, different radiation power density and repetition frequency, as well as different variants of geometric surface texture. The process was carried out in a air environment, mainly in the field of ablation texturing with "thermal effect." As a result of laser hardening, the obtained martensitic microcrystalline microstructure in the superficial zone and in the middle of the hardened zone, and martensitic - bainite and bainite in the transition zone. The microstructures with high microhardness in the range of 580 850 HV0.01 are resulting from ultrafast phase transformation occurring during the crystallization of the Fe-C-Cr-Mn-Si alloy from the liquid phase. The microstructures are in the area directly adjacent to the lubricant microchannels produced during laser texturing. It was clearly noticeable on highly fragmented microstructure and confirmed by increased microhardness. There were no micro-cracks on the surface layer, what promises great technological opportunities. The results are promising and may have a significant impact on improving the tribological associations friction pair: roller - large-size track roller bearing.

Abstract: One of the main problems with the operation of spiral bevel gears is related to very severe conditions in the contact of the meshing teeth; therefore, lubrication is very difficult, which increases the risk of scuffing occurrence. One of the ways to achieve better scuffing resistance is by the deposition of a low-friction coating on the bevel gears teeth. Gear scuffing tests were performed using a bevel gear test rig designed and manufactured at ITeE-PIB. The authorial bevel gear scuffing test was performed. Specially designed, spiral bevel gears were used for testing. Two material combinations were tested: uncoated pinion - coated wheel and, for reference, both gears without coatings. The a-C:H:W (trade name WC/C) coating of DLC type was deposited on the wheel teeth. A mineral, automotive gear oil of API GL-5 performance level was used for lubrication. It is shown that the resistance to scuffing may be significantly improved when the a-C:H:W coating is deposited on the spiral bevel gear teeth.