Residual macroscopic stress in highly preferentially oriented titanium nitride coatings deposited on various steel types

Abstract

The residual macroscopic stresses present in 1.5-mu m-thick TiN coatings on martensitic hot work tool steel and austenitic stainless steel are studied with a Theta-2 Theta decoupled x-ray diffractometer using glancing angle x-ray diffraction optics. All coatings exhibit a preferential orientation which complicates the interpretation of the conventional sin(2) Psi method. To overcome this complication, a method is used, called the fixed crystal orientation (FCO) sin(2) Psi method, in order to determine the mechanical stress in the presence of a symmetrically distributed preferential orientation. It is shown that in contrast to the glancing angle sin(2) Psi method and the conventional sin(2) Psi method interpretational problems resulting from elastic incompatibility can be avoided using the FCO method. In the TiN coatings studied a biaxial stress state can be assumed and different stress values are measured depending on the preferential orientation and the substrate material. The stress values obtained with the FCO sin(2) Psi method for the different samples are compared with the stress values obtained using the glancing angle sin(2) Psi method and the conventional sin(2) Psi method. (C) 1996 American Vacuum Society.