Investigations on Thermal Stresses of a Graded Ti(C,N) Coating Deposited on WC-Co Hardmetal

Abstract

We investigated the stress behaviour of Ti(C,N) coatings deposited on WC-Co substrates during an individual thermal cycle. The stress analyses were performed in-situ by energy dispersive X-ray diffraction using a white synchrotron beam. The stresses were determined using the sin 2 ψ method combined with scattering vector measurements at the strain-free ψ-tilt, in order to avoid the effect of the chemical C/N gradient on the strain distributions over sin 2 ψ. It was found that compressive stresses induced by top blasting on the coating are released after the individual thermal cycle. During heating and cooling, part of the Ti(C,N) coating was oxidized into a TiO 2 rutile phase. Stress analysis was also performed in this phase in order to evaluate the influence of oxidation on the residual stress of the coating. The obtained results can support the design of coated tools with improved properties at interrupted cutting operations by understanding the role of thermal cycling on the stresses of Ti(C,N) coatings.