Enhancement of the wear resistance of Ni-diamond composite coatings via glycine modification

Abstract

Experimental research on the modification of glycine to enhance the wear resistance of nickel-based diamond composite coatings was conducted in this paper. Ni-diamond composite coatings, fabricated from a plating bath, were modified by adding glycine with different contents through co-electrodeposition technology. The surface morphology, diamond content, surface roughness, nickel grain size and microhardness of the composite coatings were investigated by using scanning electron microscopy, energy dispersive spectroscopy, three-dimensional profiler, X-ray diffraction analysis and microhardness tester measurements, respectively. The tribological properties of the composite coatings were evaluated using a reciprocating ball-on-disk tester. The results revealed that the Ni-diamond composite coating with improved diamond content and optimal nickel grain size was modified by a glycine content of 10 g l−1, further increasing its microhardness by 66% to 580 HV. Simultaneously, the surface roughness was also decreased by glycine modification. Owing to the increased diamond content and the reduced surface roughness, the friction coefficient of the composite coating was effectively reduced by 33%. With increasing microhardness and decreasing friction coefficient, the wear rate of the composite coating was reduced by 53%, and the cutting volume was increased by 60%, thus significantly enhancing the wear resistance of the coatings.