Study on Fretting Wear Properties of High Speed Diesel Engine Roller Tappet Material Cr12W Steel

The cam and tappet are key components of the internal combustion engine valve train system. Due to the alternating high-frequency cyclic of high contact stress, the cam and tappet are prone to abnormal wear and failure. In this work, Cr12W steel was selected as the material of the roller tappet in valve train. Then, it was treated by ion nitriding treatment. The fretting wear tests were carried out under laboratory conditions. The wear mechanisms of nitrided and untreated specimens which rubbed with GCr15 steel were investigated under dry friction and oil lubrication, respectively. It is found out that the predominant wear mechanisms of nitrided specimens under dry friction are slight abrasive wear and adhesive wear, whereas under oil lubrication, it is mainly spalling. The wear mechanisms of untreated specimens under dry friction are identified as adhesive wear and oxidative wear, while it is mainly abrasive wear under oil lubrication.