Comparison of tribological properties of HVOF sprayed coatings with different composition

Abstract

This paper presents the results of a comparative study conducted to compare the friction and wear behavior of five high velocity oxy fuel (HVOF) sprayed coatings sliding against Al2O3 counter body under dry conditions. Single way ball-on-disk tests were performed on NiCrBSi/WC (50/50), NiCr (80/20), WC/Co (88/12), WC/CoCr and Cr3C2/NiCr (75/25) coatings, deposited on stainless steel substrates, under normal load of 5, 15N and sliding speed of 10, 20cm/s. To understand the wear process, detailed XRD and SEM analysis in combination with EDS of the worn coatings were performed. The results show that the most suitable HVOF sprayed coating to prolong the lifetime of components working at high temperature and wear conditions is WC/CoCr coating owing to its lowest friction coefficient and highest wear resistance. It is followed by WC/Co, Cr3C2/NiCr and NiCrBSi/WC. The NiCr coating exhibited the worst performance at all conditions. Wear volume of the coatings generally increased with the increase in both normal load and sliding speed, while WC/CoCr coating is adversely affected from the normal load. Wear rate decreased with decreasing sliding speed and increasing normal load. The coatings were generally worn by abrasion wear, including particle pull-out and scratching. Plastic deformation was also observed on the surface of softer coatings such as NiCr.