US Patent 7658173 Tappet for an internal combustion engine

A tappet for an internal combustion engine is formed from a high-carbon, bearing grade steel. The high-carbon, bearing grade steel has a relatively high surface fatigue strength that provides the tappet with the ability to absorb a relatively large contact stresses during operation, thereby minimizing the formation of cracks within the tappet. Additionally, the high-carbon steel tappet can be heat treated to provide a substantially uniform hardness, between about 58 Rockwell Hardness C (HRC) and 62 HRC, and a substantially consistent microstructure throughout the tappet, thereby minimizing wear of the tappet during use.