High-temperature wear properties of gradient microstructure induced by ultrasonic impact treatment

•A gradient microstructure is formed by ultrasonic impact on low-carbon steel.•The gradient microstructure can increase high-temperature wear properties.•The wear mechanism becomes different under different applied loads. The high-temperature wear properties of the gradient microstructure formed by ultrasonic impact treatment (UIT) on the surface of low-carbon steel are investigated. The dominant wear mechanism of the sample is oxidation wear and adhesive wear as the temperature increased from 300 °C to 500 °C. The wear mechanism of the sample changed from abrasive wear to fatigue wear as the applied load increased from 15 N to 95 N. The improvement in the high-temperature wear properties is due to the gradient nanocrystallization, which is helpful for forming an oxide film during wearing. As well as due to presence of the grain boundary wetting phase transitions of cementite, which can effectively delay the crack initiation.