Preparation and Wear Resistance of Composite Coating on Surface of Mechanical Hydraulic Rod

Mo-(NiCr-Cr₃C₂) composite coatings with different Mo content were prepared by plasma spraying on the surface of mechanical hydraulic rod made of 45 steel. The morphology, mechanical properties and wear resistance of the composite coatings were tested by scanning electron microscopy, tensile testing and friction-wear testing. The friction and wear mechanism was also analyzed. The results show that the cross-sections of Mo-(NiCr-Cr₃C₂) composite coatings displayed layered structure. The white phase in the coatings was Mo, the black-gray phase was Cr₃C₂, and the gray phase was adhesive phase NiCr. With the increase of Mo content, the porosity and micro-hardness of the composite coatings decreased gradually, the bonding strength first increased and then decreased, and the bonding strength of 80NCC coating was the highest. The wear volume of the composite coatings was smaller than that of pure Mo coating. And the 80NCC coating had low friction coefficient, minimum wear volume and small wear loss of abrasive part. The wear resistance of Mo-(NiCr-Cr₃C₂) composite coatings with different Mo content was linearly related to the ratio of hardness to elastic modulus of the coatings. The 80NCC coating had the largest value of ratio of hardness to elastic modulus and the best wear resistance in the composite coatings.