Microstructure and Wear Properties of Friction Induced Nano-crystalline Surface Layers of Carbon Steels

Pin-on-disc sliding friction tests were carried out for 0.45 mass % carbon steels, and TEM microstructure and hardness of the sub-surfaces of the friction specimens were investigated. Particularly effects of friction conditions on the microstructure at the surfaces and wear properties of the friction induced microstructure were studied. It was found that ultra-fine equi-axed grains in the 30 - 50 nm size range were produced in the case of a high friction speed of 5.0 m/s in an air atmosphere. Moreover, nano-crystalline microstructure can be produced in a vacuum atmosphere even if the friction speed was low. The friction induced nano-crystalline surface layers, which exhibited significant high hardness, showed good wear resistance.