Investigation of the Fretting Friction and Wear Characteristics of G20Mn5QT Cast Steel Laser Cladding 316L Layer

Fretting wear is widely existed in the field of rail transportation, surface engineering technology can effectively improve the anti-fretting wear performance of parts and components, which is of great theoretical significance and industrial value to guarantee the safe service of rolling stock. In this paper, 316L stainless steel powder cladding layer was prepared on the surface of G20Mn5QT cast steel substrate by laser cladding technology. The tangential fretting wear tests of G20Mn5QT cast steel substrate and 316L cladding layer were carried out by using a self-developed fretting wear tester. The tests were performed in ball/plane contact mode, examining the tangential fretting damage mechanism and damage evolution rules under various displacement amplitudes (10, 20 and 40 μm) with a fixed normal load of 30 N. The surface phase and wear area surface morphology of the cast steel substrate and 316L cladding layer were analyzed using X-ray diffractometer (XRD), scanning electron microscope (SEM), white light interferometer, electron energy dispersive spectrometer (EDS) and other equipment. Additionally, the chemical elements of the wear marks were analyzed and characterized. The results indicated that after laser cladding of 316L coating, the Cr-containing hard phases, such as Cr_0.19Fe_0.7Ni_0.11 generated during the laser cladding as well as the homogeneous metallographic organization increased the hardness of the coating surface by 14.3%. Under normal load of 30 N, the fretting operating state of the cast steel substrate and the cladding coating transitions from the partial slip zone to the mixed zone to the complete slip zone as the displacement amplitude increased. During the stable stage, the friction coefficient gradually rised, leading to an escalation in wear scar damage. The damage mechanisms in the partial slip zone involved adhesive wear for both the cast steel substrate and cladding layer. In contrast, the mixed zone and complete slip zone experienced abrasive wear, delamination, and oxidation wear. The damage degree of 316L cladding layer was slightly lower than that of cast steel substrate. In the mixed zone and slip zone, the wear rate of 316L cladding layer was about 4.26% and 19.1% lower than that of G20Mn5QT cast steel substrate. Compared with G20Mn5QT cast steel substrate, 316L cladding layer showed higher fretting wear resistance.