Experimental investigation of friction and wear of Mo ion implanted ferritic/pearlitic steel

The paper presents the results of a comparative experimental investigation of friction and wear behavior of the ferritic/pearlitic medium-carbon steel (in wt.% 0.45 C) in the initial and implanted states. New approach to description of plastic deformation and destruction under friction is introduced on the basis of concepts of structural levels of plastic deformation and physical mesomechanics. The ‘Diana-2’ vacuum-arc metal ion source was used for the ion implantation. The Mo ions were implanted at an accelerating voltage of 60 kV to a dose of 1·1017 ion·cm−2. Tribotechnical tests were carried out using the ‘ring-on-block’ sliding wear machine at a sliding speed of 1 m/s and a 150 N normal load. AES was used to define concentration profiles. The microstructure was investigated using TEM. SEM was used to investigate morphology of wear tracks and debris particles. In order to investigate the plastic deformation behavior under friction, the original method was applied using the ‘TOMSC’ television-optical measuring technique. It has been found that the debris particles and wear tracks, the sizes of which correspond to the three structural levels, are formed during wear testing of the initial and implanted specimens. The debris particle sizes of level 1 (units of micrometers) correspond to the microstructure fragment sizes. The debris particle sizes of level 2 (tens of micrometers) are correlated with the mesostructure fragment sizes. The debris particle sizes of level 3 (hundreds of micrometers) correspond to the vortex mesostructure sizes. It was concluded that the formation of the modified structural-phase state in the surface layer of the Mo ion implanted specimens prevents the fragmented structure formation at mesolevel and retards the mesofragment vortex movement in the subsurface layer, thereby decreasing the intensity of the debris particle formation and finally increasing wear resistance.