Fretting wear behaviour of high-nitrogen stainless bearing steel under lubrication condition

Abstract

The fretting wear performance of high-nitrogen stainless bearing steel (40Cr15Mo2VN) under lubrication conditions was researched. Lithium-based grease was prepared by using MoS₂ and carbon nanotubes (CNTs) as additives. AISI 52100 steel ball was used in four-ball test to evaluate the extreme pressure property and wear resistance of grease. After four-ball test, the grease adding 0.8 mass% MoS₂ and 0.8 mass% CNTs, respectively, was chosen and used for fretting test. AISI 52100 ball and 40Cr15Mo2VN steel disc were used as the upper and lower samples for fretting test. The results showed that wear power consumption increased with the increase in both sliding velocity and contact stress. When initial contact stress was 2.047 GPa, the main wear mechanisms were abrasive wear and plastic deformation as the velocity increased from 0.028 to 0.112 m/s. When the velocity was 0.028 m/s, the main wear mechanisms changed from abrasive wear to adhesion wear and finally to abrasive wear and adhesion wear as the initial contact stress increased from 1.788 to 2.579 GPa. The volume loss grew sharply because of the changes in wear mechanisms. In this condition, the volume loss growth rate can be divided into three regions according to different wear power consumption ranges corresponding to different wear mechanisms.