A Study on the Tribological Behavior of Camshaft by CrN plus WC/C Coating

Abstract

The contact in the valve train system is known to be the part subject to significant load in an automobile engine. For such reason, the wear of the contact accounts for the greatest portion of entire friction loss of an engine, leading to the occurrence of abnormal wear. Recently, with the increase in the fuel economy of an engine as well as the durability increase becoming the critical goals to engine developers, many studies are being performed on the reduction of wear in the valve train system. In order to reduce the wear in the valve train, this study first formed a CrN layer to increase the bonding force with the base metal using the PVD-sputtering coating method and then applied a 2-layer coating that formed the WC/C layer with low friction/wear resistance characteristics. In addition, it examined the friction characteristics occurring between the cam and the tappet by using the dedicated wear tester and found that the friction torque value was reduced approximately 60-70% in the high load condition through comparison testing with the existing part when the CrN +WC/C coating was applied. And vibration was reduced by 50%. So application of the CrN +WC/C coating to actual vehicles will reduce the fuel economy and occurrence of noise-vibration.