Research Progress on Fatigue Life of HVOF Tungsten Carbide Cermet Coating

High velocity oxygen fuel (HVOF) sprayed WC cermet coating possesses high hardness, high bonding strength and nearly full-density, which are the candidates of EHC (electrolytic hard chromium). In the present paper, the research status quo of the influence of HVOF sprayed WC coating on the fatigue life of the substrate was summarized and the reasons of crack initiation and fatigue life decrease were also analyzed. The factors affecting the fatigue life are as follows: the difference between the coating and the substrate in properties, the defects introduced by grit blasting, residual stress and coating preparation. The improvement measures include coating gradient design, change of the pre-treatment such as shot peening replacing grit blasting, obtaining or increasing the coating compressive stress, reducing the decomposition of carbide, reasonable process parameters (such as high speed), proper coating thickness, applying WC powder with high content of binder, appropriate post-treatment of the coating.