On tribological behaviour and application of TiN and MoS 2-Ti composite coating for enhancing performance of monolayer cBN grinding wheel

Abstract

Application of MoS 2-based solid lubricant has extreme potential as a coating material of cutting tools because of its superlubricity against most of the engineering materials. However, a detailed study on the effect of such lubricious coating in grinding has never been carried out before. In the present research, the tribological behaviour of MoS 2-Ti composite coating with TiN underlayer on electroplated nickel and braze alloy was investigated separately in comparison to TiN coated and uncoated counterparts. Grinding of AISI 52100 steel was also carried out with uncoated, TiN coated and MoS 2-Ti coated (with TiN underlayer) monolayer (both electroplated and brazed) cBN wheels. The structure of the coatings and the condition of the grinding wheels were observed under SEM. In tribology test, MoS 2-Ti composite coating was found to be best performing on both nickel and braze alloy in terms of coefficient of friction and depth of the wear track. Minimum variation in normal force and remarkably steady behaviour of tangential force were obtained with both MoS 2-Ti coated electroplated and brazed wheels over the total experimental run. Large number of grit fracture at and above bond level with some amount of grit pull-out was observed in uncoated electroplated wheels. Uncoated brazed wheels have undergone grit breakage at bond level. However, such failures of grit were significantly arrested with both TiN and MoS 2-Ti composite coatings.