Microstructure and Wear Resistance of High Volume Fraction Carbide (Cr,Fe)₇C₃ Reinforced Fe Based Coating

An anti-wear coating with high volume fraction hexagonal prism carbide (Cr,Fe)₇C₃ as the reinforcing phase was fabricated by in-situ reaction method on a low carbon steel Q235 plate by plasma cladding process with FeCrNiBSi and Cr₃C₂ powders. Microstructure of the coating was characterized by using optical microscopy, scanning election microscopy, X-ray diffraction, energy dispersive spectrometer. Wear tests were conducted on a M-2000 tester with the constant load and variable load. The results show that the coating mainly consisted of primary carbide (Cr,Fe)₇C₃, α-Fe and the uncompletely dissolved Cr₃C₂. The hexagonal prism carbide (Cr,Fe)₇C₃ had high volume fraction (about 75.5%), high microhardness (about HV_0.5 1 218～1 524) and uniformly distributed in the coating. The carbide was resposible for the relative wear resistance of the (Cr,Fe)₇C₃ coating 9 times and 14 times as that of FeCrNiBSi coating under constant and variable load. The main wear mechanism of the (Cr,Fe)₇C₃ carbide reinforced coating was cracked and spalled brittlely of the carbide under high tangential stress. Then, with the increasing loads, the wear mechanism of coating was transformed from abrasive wear to oxidation wear.