Effects of Fuel Type and Spraying Parameters on Microstructure and Mechanical Properties of HVOF Sprayed WC10Co4Cr Coatings

HVOF sprayed WC-based cermet coatings have been widely used in industries for wear, corrosion and cavitation protection of the metallic components. WC10Co4Cr coatings were deposited by gas fuel-HVOF (GF-HVOF) and liquid fuel-HVOF (LF-HVOF) processes at 9 different spraying conditions to investigate the effect of fuel type on microstructure, residual stress and mechanical properties of HVOF cermet coatings. For the coatings prepared at optimized conditions, residual stress raised in the coatings was in-situ monitored by testing the curvature evolution of the substrate during spraying. Vickers microhardness, indentation and ball-on-disc wear test were performed to evaluate mechanical properties of the resultant cermet coatings. The results show that cermet particles have higher velocity and lower surface temperature in LF-HVOF than those in GF-HVOF. A compressive residual stress is formed in the LF-HVOF WC10Co4Cr coating while a residual stress is detected in the GF-HVOF coating. Because of combination of more compact microstructure and compressive residual stress, the LFHVOF cermet coating (1280 HV0.3, 7.3 MPa.m(0.5)) shows both higher hardness and higher fracture toughness and thereby higher wear resistance than that of CF-HVOF coating (1032 HV0.3, 4.5 MPa.m(0.)(5)).