Effects of various laser cladding materials on the tribological properties of damaged wheel treads under various temperatures and humidities

Laser cladding technology is used to repair damaged wheels and plays an important role in prolonging their service life. Additionally, the temperature and humidity of the environment have important effects on the operation of the repaired wheels. In this study, widely used 316 L and 420 stainless steel alloy powders were selected as cladding materials, and three environmental conditions (25℃-RH60 %, 50℃-RH60 %, and 50℃-RH90 %) were set according to changes in temperature and humidity in different areas of China. Friction and wear tests were performed under different temperature and humidity conditions on a damaged wheel after local repair by laser cladding. The results clearly show that there are demarcated equiaxed and directional columnar grain regions in the 316 L cladding, whereas there are uniform plate and strip martensite structures in the 420 cladding, which are well formed by the metallurgical bonding of the wheel substrate. From 25℃-RH60 % to 50℃-RH90 %, the friction coefficient, plastic deformation thickness, and wear rate of the wheel–rail tended to decrease. However, the wear rates of the 420-coated wheels increased as the environmental conditions increased from 25 °C-RH60 % and 50 °C-RH60 %, and the wear rates of the corresponding rail samples remained high. The main forms of surface damage are fatigue cracks and material spalling. With increasing temperature and humidity, the damage to the bonding zone between the cladding and substrate surface decreases. The damage to the cladding profile is caused mainly by cracks at different angles and spalling pits. In the 25 °C-RH60 % environment, cracks initiate in the profile of the bonding zone and propagate along the plastic rheological line to the interior of the material. In comparison, the locally repaired wheel with 316 L stainless steel alloy powder as the laser cladding material has better tribological properties and is more suitable for repairing damaged wheels.