Microstructure and Tribological Performances of Laser Cladded Ni–Mo–Cr3C2 Coatings Under Grease-Lubrication Condition

Ni–Mo–Cr 3 C 2 system coatings with the different Cr 3 C 2 mass fractions were prepared on GCr15 bearing steel by laser cladding (LC). The microstructure and phases of obtained coatings were analyzed using an ultra-depth of field microscope (UDFM) and X-ray diffractometer (XRD), respectively. The friction-wear performance of Ni–Mo–Cr 3 C 2 coatings under the grease-lubrication condition was investigated using a ball-disc-wear test, and the wear mechanism was also discussed. The results show that the Ni–Mo–Cr 3 C 2 coatings have a strong dendritic structure, in which the Cr 3 C 2 with the spherical shape is distributed on the coatings. The hardness of Ni–Mo–5Cr 3 C 2 , –15Cr 3 C 2 and –25Cr 3 C 2 coatings is 990 ± 29, 1018 ± 33, and 1316 ± 27 HV 0.5 , respectively, higher than 540 ± 30 HV 0.5 of substrate. The average coefficients of friction (COFs) of Ni–Mo–5Cr 3 C 2 , –15Cr 3 C 2 and –25Cr 3 C 2 coatings are 0.12 ± 0.07, 0.11 ± 0.05, and 0.10 ± 0.04, respectively, and the corresponding wear rates are 71.9 ± 3.3, 40.1 ± 2.4, and 19.9 ± 2.7 μ m 3 s −1 N −1 , respectively, which decrease with the increase of Cr 3 C 2 mass fraction. The reinforcing phase of Cr 3 C 2 exhibits the excellent performance of friction reduction, which also further improves the wear resistance. Moreover, the grease storage in the pores plays the role of friction reduction, in which the lubrication effect of round-edged pores is better than that of sharp-edged pores.