Application of Super Carburizing to Hydraulic Lash Adjuster

As hydraulic lash adjuster (HLA) gives great advantages to valve trains such as less maintenance cost, no variations in load exchange and engine power and so forth, the number of engines equipped with HLA is increasing. Being contact-loaded by cams or rockers, the contact face of HLA is usually case hardened or coated with wear resisting materials. The study was made to apply super carburizing to HLA to improve wear, pitting and scuffing resistance. Super carburizing is characterized by its carbide precipitation in case due to higher carbon contents than in conventional gas carburizing. Super carburizing was appplied to cam follower type HLA in trial using the newly alloy designed steel, 0.17 C-0.5Si-2.25Cr-0.4Mo. It was found that the super carburized HLA showed higher endurance life than gas carburized one and almost the same properties as wear resisting material coated one.