Revealing fretting wear resistance mechanism under liquid lead-bismuth eutectic of Cr-Al-C composite coatings fabricated by laser cladding

Abstract

Laser cladding technology was utilized to construct protective coatings on the surfaces of service materials and to study the mechanical and fretting wear properties of the coatings. The coating mainly consists of diffuse Cr2AlC phase, interdendritic Cr7C3 phase and dendritic Cr-based solid solution. The hardness of the coating was enhanced to 690 HV, which is 3.1 times higher than the hardness of the substrate. The change in H3/Er2 values of the coating and the substrate were calculated by nanoindentation to be 0.04 and 0.024, respectively, and the anti-fretting wear properties of the coating was excellent. The statistical distribution of the Schmidt factor of the coatings is between 0.41 and 0.5, which indicates that the coatings have a high probability of initiating slip and high plastic deformation capacity. For those grains with large Schmidt factors, dislocations can be easily activated in response to applied stresses. Strength is the first element of wear resistance, and with sufficiently high strength, the plasticity enhancement can be very effective in improving the fretting damage resistance. After the fretting wear test in liquid LBE, the Cr-Al-C composite coating has a huge increase in wear resistance compared to the substrate. The wear resistance of the coating was 33 times that of the 316 stainless steel substrate at a test temperature of 450 °C