Investigation of anti-galling and low friction properties of laser processed co-based materials

Abstract

The anti-galling and low friction properties of a CO2-laser processed Co-based material (Stellite 21) was investigated under high-load sliding conditions. Dry sliding tests were carried out at both room temperature and at 250 °C. The tests were carried out by sliding two identical specimens against each other in a dedicated test.A low and stable friction coefficient at a level of about 0.20, and relatively independent on load and sliding speed, was obtained after a short running-in period. No tendency to galling was observed in any test.During sliding, the superficial fcc material transforms to hcp with the {0001} planes preferentially orientated parallel to the surface of the wear track. Since these planes are easily sheared, and supported by a deformation hardened zone, a surface layer is generated with low friction properties and high resistance to galling. Thus, the laser processed Co-based alloy exhibits the functional ability to generate a surface with unique properties during sliding contact.The anti-galling and low friction properties of a CO2-laser processed Co-based material (Stellite 21) was investigated under high-load sliding conditions. Dry sliding tests were carried out at both room temperature and at 250 °C. The tests were carried out by sliding two identical specimens against each other in a dedicated test.A low and stable friction coefficient at a level of about 0.20, and relatively independent on load and sliding speed, was obtained after a short running-in period. No tendency to galling was observed in any test.During sliding, the superficial fcc material transforms to hcp with the {0001} planes preferentially orientated parallel to the surface of the wear track. Since these planes are easily sheared, and supported by a deformation hardened zone, a surface layer is generated with low friction properties and high resistance to galling. Thus, the laser processed Co-based alloy exhibits the functional ability to generate a surface with unique properties during sliding contact.