Friction And Wear Behaviors Of Plasma Nitrided 2Cr13 Stainless Steel In Vacuum

A nitrided layer with the approximately 116μm thickness was formed on the quenched and tempered 2Cr13 stainless steel by plasma nitriding. The investigation was carried on composition, microstructure, and the distribution of hardness and residual stress in the nitrided layer. The friction and wear properties of the unnitrided and the plasma nitrided 2Cr13 steel were systematically measured in air and in vacuum using a pin-on-disc vacuum friction and wear test machine. The influence of surface temperature, friction velocity, and load on the tribological property, the feature of the worn surface, and the wear mechanism in vacuum for the plasma nitrided 2Cr13 steel was analyzed.The results show that, a nitrided layer is generated through plasma nitriding, which has a certain grads distribution of hardness and residual stress. The nitrided layer is consisted of compound layer and diffusion zone. The compound layer is mainly composed ofγ′-Fe4N and a small amount ofε-Fe3N. The unnitrided 2Cr13 steel exhibits intensive plastic deformation during friction both in air and in vacuum. In contrast, the plasma nitrding improves the friction coefficient and adhesion wear in air, and significantly increase the wear resistance in vacuum.The friction coefficient shows a slight decrease with increasing velocity. Excepting to the relatively high wear under the condition of high loads and velocities due to the transition of wear mechanism from the mild abrasion to delemination, velocity has slight effect on the wear loss of the nitrided 2Cr13 steel in vacuum. With increasing load, the friction coefficient is slightly decreased and the wear loss is increased in vacuum especially under high loads and velocities a sever wear existing. Increasing velocity and load, the wear transforms from abrasive wear to slight adhesion and even delemination under high loads and velocities.Under low velocities and loads in vacuum, the worn surface is characterized by small debris. With increasing velocity and load, scale-like morphology produced by plastic deformation appears on the worn surface. In the case of high loads and velocities, there are morphologies of scaled microstructure of plastic deformation, microcracking, and intergranular fracture existed on the worn surface, and the amorphous, a thin sever deformed zone as well as plastic deformation flows in the worn surface layer. The increase in surface temperature is related to the variation in wear mechanism. The abrasive wear leads to lower temperature rising, while the higher elevated temperature is corresponding to the adhesion wear in vacuum.