RESIDUAL MACROSCOPIC STRESS IN HIGHLY PREFERENTIALLY ORIENTED TITANIUM NITRIDE COATINGS DEPOSITED ON VARIOUS STEEL TYPES

The residual macroscopic stresses present in 1.5-mu m-thick TiN coatin gs on martensitic hot work tool steel and austenitic stainless steel a re studied with a Theta-2 Theta decoupled x-ray diffractometer using g lancing angle x-ray diffraction optics. All coatings exhibit a prefere ntial orientation which complicates the interpretation of the conventi onal sin(2) Psi method. To overcome this complication, a method is use d, called the fixed crystal orientation (FCO) sin(2) Psi method, in or der to determine the mechanical stress in the presence of a symmetrica lly distributed preferential orientation. It is shown that in contrast to the glancing angle sin(2) Psi method and the conventional sin(2) P si method interpretational problems resulting from elastic incompatibi lity 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 m aterial. The stress values obtained with the FCO sin(2) Psi method for the different samples are compared with the stress values obtained us ing the glancing angle sin(2) Psi method and the conventional sin(2) P si method. (C) 1996 American Vacuum Society.