Characterization and Evaluation of Tribological Properties of NiCrBSi-Gr Composite Coatings Deposited on Stainless Steel 420 by HVOF.

Ni-based alloys are resistant against wear and corrosion, and are widely applied in surface engineering. In this study, different amounts of graphite (0, 5 and 10 wt.%) are added to NiCrBSi powder as a solid lubricant. The pure and composite powders are deposited on 420 stainless steel through the high-velocity oxygen fuel process. The microstructure and properties of the coatings are examined through x-ray diffraction and scanning electron microscope. Vickers microhardness test is run for the coatings' hardness measurement. NiCrBSi has the highest hardness of 650HV. Hardness of the coatings decreases with the increase in the graphite content. The porosity measurement by ImageJ analyzer indicates that the NiCrBSi coating has the lowest porosity. To assess the ambient and high-temperature wear resistance of the coatings, ball-on-disk wear tests were run with 15 N load and the sliding distance of 1000 m at 25 °C and 450 °C. The results indicate that the NiCrBSi and NiCrBSi-10 wt.%Gr coatings have the highest wear resistance at ambient and high temperatures, respectively. The friction coefficient of the coatings containing lubricant is lower than that of the NiCrBSi coating. [ABSTRACT FROM AUTHOR]