Tribological coatings for improving cutting tool performance

Abstract

With an increasing usage of advanced high-strength steels, there is an escalating need for improvements in cutting tool performance for these alloys. In this study, the tribological performances of Cr2N, WC/a-C:H, and Ti-MoS2 coatings on AISI M2 steel were examined. Surface treatments were evaluated using dry pin-on-disk testing, Charpy impact testing, and a reciprocating impact-sliding test rig (RISTR) designed to replicate the interaction between cutting tools and high-strength steel sheet. Charpy testing of coated specimens showed no statistical change in impact toughness from the untreated steel. Pin-on-disk testing was performed to quantify the friction and wear of untreated and coated tool steel. These tests showed that Ti-MoS2 coated tool steel had the lowest friction coefficient, and Cr2N, the lowest wear rate. Impact tribometer testing showed that the Ti-MoS2 coating yielded an increase of 370% in the number of cycles to failure over untreated specimens, while the WC/a-C:H coating was found to decrease the number of cycles to failure over untreated specimens. With an impact stress lower than the compressive yield strength of the AISI M2 steel, the fatigue life of the surface treatments scaled approximately as E2/H3, the inverse of the resistance to plastic deformation.