Influence of Micro structure of Steel on the Antiwear Properties of Some Additives

The influence of chemical composition, mechanical parameters and microstructure of steel on the antiwear properties of three types of additives (S, P and P-N agent) have been examined using a four ball test machine and a HQ-1 tester. The materials used in the four ball tests were three alloys with different elemental compositions. Both the upper block specimen and lower ring specimen were made of G20CrNi2MoA steel and all the lower ring specimens met the identical specification. The upper block specimens were treated to obtain specimens with different microstructures and hardness levels. The preliminary results indicated that chemical composition, mechanical properties and microstructure all had important effects on the wear performences of the additives. In certain instances microstructure could completely dominate wear properties of the additives. In case of the block specimens tempered at lower temperature after oil quenching and the block specimens tempered at lower temperature after water quenching the resulting microstructures all belonged to tempered martensite. Supri-singly, the former was much more effective than the later in reducing wear. The films formed on the rubbing surfaces by the additives as well as the metallic layer immediately below these reaction films have been investigated with XPS, AES and Mossbauer spectroscopy. Surface analysis suggested that the lower wear of block specimens tempered at lower temperature after oil quenching associated to the formation of thick chemical reaction films, the lack of residual austenite component as well as the higher surface reactivity. The possible mechanisms responsible for the interaction between materials and additives were discussed. It was emphasized that if the fundamental research would make a significant contribution to the material selection in industrial applications, it should focus atten-tion on the compatibility between the steel and additives.