Effects of temperature on the friction-wear properties of 40Cr steel by warm extrusion

A forming experiment of 40Cr steel was conducted by using a warm extrusion technology, and the friction-wear behavior of the samples at different extrusion temperatures were observed. The wear morphologies, distributions of chemical elements and phase compositions were analyzed by scanning electronic microscopy (SEM), energy diffusive spectrometry (EDS), and X-ray diffraction (XRD), respectively, and the wear mechanism of warm extrusion on 40Cr steel was discussed. The results show that the grains are samll by warm extrusion at 550℃, the content of retained austenite is higher, and the hardness is the highest, showing that the wear resistance is the best. The size of grains is bigger and the contents of retained austenite decrease at the extrusion temperature of 650℃ and 750℃. The coefficient of friction is 0.7667 at the extrusion temperature of 550℃ under the load of 5 N, while that is 0.8587 at the extrusion temperatures of 650℃, which increases by 12.01%, and the wear performance decreases. At the extrusion temperature of 750℃, the coefficient of friction is 0.8764, which increases by 14.31% compared with 550℃, and the wear performance is worse. The wear forms of the samples at 550, 650 and 750℃ are common abrasive wear.