Dry Sliding Wear Behavior of (Cr, Fe)7C3-γ(Cr, Fe) Metal Matrix Composite (MMC) Coatings: The Influence of High Volume Fraction (Cr, Fe)7C3 Carbide

The high volume fraction (Cr, Fe)(7)C-3 carbide particle-reinforced metal matrix composite (MMC) coatings with different Cr/C ratios were produced by flux-cored arc welding (FCAW). The in situ synthesized effectiveness of (Cr, Fe)(7)C-3 carbide in the coatings was studied by the aid of CALPHAD and differential scanning calorimeter. The microstructure of the coatings was observed by optical microscope and field emission scanning electron microscope, and their phases were determined by the X-ray diffraction. Meanwhile, the hardness and wear resistance of the coatings were measured. The results show that the (Cr, Fe)(7)C-3 carbide can be in situ synthesized in the coatings. With decreased Cr/C ratio, the in situ synthesized effectiveness of (Cr, Fe)(7)C-3 carbide is improved and the mass fraction of the (Cr, Fe)(7)C-3 carbide is increased. The microstructure of the coatings consists of in situ synthesized (Cr, Fe)(7)C-3 carbide and eutectic (Cr, Fe)(7)C-3/ gamma (Cr, Fe) matrix. The hexagonal-rod-form (Cr, Fe)(7)C-3 carbide can be fractured and segregated from austenite-matrix under a relatively high load force (50 N), and transforms the wear state from two-body-abrasion to three-body-abrasion, which facilitates the coating be seriously abraded and even adhered. The wear resistance of the MMC coatings can be effectively improved by the formation of high volume fraction of (Cr, Fe)(7)C-3 carbide.