: In this study, high-velocity oxygen-fuel (HVOF) process was applied to create a composite coating on the surface of stainless steel 420 samples. The effect of graphite addition as solid lubricant on properties of HVOF sprayed NiCrBSi-Gr coatings was investigated. Various amounts of graphite powder 0%, 5% and 10% were mixed with NiCrBSi powder for 1 hour. Then, powders deposited on stainless steel 420 substrate with HVOF method. Evaluation of microstructure and properties of obtained composite coatings was done by X-ray diffraction (XRD) and scanning electron microscope (SEM). Vickers micro hardness test was used to evaluate the hardness of coatings. Cyclic oxidation test in 800?C for 50 hours were performed to evaluate the oxidation resistance of coatings. Also, the ball-on-disk tests with 15N load and 1000m sliding distance at 25?C and 450?C were used to cold and hot wear resistance assessment of coatings. The results indicated that the NiCrBSi and NiCrBSi-10wt%Gr coatings exhibit maximum wear resistance at room temperature and high temperature, respectively. Friction coefficient of coatings containing solid lubricant was lower than NiCrBSi coating. The NiCrBSi-10wt%Gr coating exhibited high porosity (3.2%), but NiCrBSi coating had the lowest porosity of all. The ?-Ni was the main phase in all coatings. Further more, carbide phases (Cr 7 C 3 and Cr 23 C 6 ) and boride phases (Ni 3 B and CrB) were observed in all coatings. High temperature oxidation test indicated that NiCrBSi coating exhibits the best behaviour in comparision to other samples. Keywords: NiCrBSi coating, friction coefficient, HVOF method, graphite, solid lubricant, wear, high temperature oxidation
