Micro-Structures and High-Temperature Friction-Wear Performances of Laser Cladded Cr-Ni Coatings

Cr-Ni coatings with the mass ratios of 17% Cr-83% Ni, 20% Cr-80% Ni and 24% Cr-76% Ni were fabricated on H13 hot work mould steel using a laser cladding (LC). The surface-interface morphologies, chemical elements, surface roughness and phase composition of the obtained Cr-Ni coatings were analysed using a scanning electron microscope (SEM), energy disperse spectroscopy (EDS), atomic force microscope (AFM) and X-ray diffractometer (XRD), respectively. The friction-wear properties and wear rates of Cr-Ni coatings with the different mass ratios of Cr and Ni at 600 °C were investigated, and the worn morphologies and wear mechanism of Cr-Ni coatings were analysed. The results show that the phases of Cr-Ni coatings with mass ratios of 17% Cr-83% Ni, 20% Cr-80% Ni and 24% Cr-76% Ni are composed of Cr + Ni single-phases and their compounds at the different stoichiometry, the porosities on the Cr-Ni coatings increase with the Cr content increasing. The average coefficient of friction (COF) of 17% Cr-83% Ni, 20% Cr-80% Ni and 24% Cr-76% coatings are 1.10, 0.33 and 0.87, respectively, in which the average COF of 20% Cr-80% Ni coating is the lowest, exhibiting the better anti-friction performance. The wear rate of 17% Cr-83% Ni, 20% Cr-80% Ni and 24% Cr-76% Ni coatings is 4.533 × 10^-6, 5.433 × 10^-6, and 1.761 × 10^-6 N^-1·s^-1, respectively, showing the wear resistance of Cr-Ni coatings at a high temperature increases with the Cr content, in which the wear rate is 24% Cr-76% Ni coating with the better reducing wear. The wear mechanism of 17% Cr-83% Ni and 20% Cr-80% Ni and 24% Cr-76% coatings at 600 °C is primarily adhesive wear, and that of 24% Cr-76% coating is also accompanied by oxidative wear.