Effect of Ni-Cr-Si-B alloy based composite powder content, production technology and spraying methods on the wear resistance of gas-thermal coatings.

Abstract

The main goal of this work is to investigate the effect of self-fluxing alloy based composite powder with TiB2 and WC particles additives production and spraying technology on the gas-thermal coating microstructure and wear-resistance under dry sliding conditions. The comparative analysis of wear resistance of plasma-sprayed and HVAF-sprayed coatings was performed. The NiCrSiB-based composite powders with 20wt.% of TiB2 particles additives were produced by various tech-nologies: NTB-20C powder was fabricated by the method of conglomeration with organic binder and NTB-20S powder was produced by bulk composite material sintering in vacuum and crushing. Commercially available powder ПС-12НВК-01 was used to deposit the composite gas-thermal coating of (Ni-Cr-Si-B)-WC system. It was determined that composite powder production technology influence significantly on the coatings wear resistance. The wear-resistance of NTB-20S coatings was 1,5 - 2,5 times better than NTB-20C coatings wear-resistance. Using scanning electron microscopy it has been found that during sintering process of NiCrSiB-20%wt.TiB2 bulk composite material the chromium-titanium boride and carbide grains are formed. The microhardness of chromium-titanium boride and carbide grains is equal to 22,9 - 25,4 GPa. It was determined that NTB-20S coatings has highest wear-resistance. Regardless of the spraying method their wear rates were in the range of 22 - 28 μm/km. Under dry sliding conditions the friction coefficient rates of the NTB coatings were within the range of 0,2 - 0,6. However, the friction coefficient rates of NTB HVAF-sprayed coatings were higher as compared with NTB plasma-sprayed coatings.