Residual stress in coated low-Z films oF TiC and TiN: I. Stress measurement by use of X-ray diffractometry

Abstract

Residual elastic stress measurement by detecting the shift of diffraction angle 2θ of a lattice plane with a particular (hkl) set against the change of angle between surface normal of specimen and diffraction plane normal ψ is explained. The advantage of this method is emphasized in comparison with usual X-ray method which must rely on some standard stress-free lattice constant as a reference. Measurements are done on TiN and TiC films coated onto Mo, Inconel and Pocographite by PVD and/or CVD methods. Values of the residual stresses range from 2.38 × 10 8 dyn/ cm 2 in TiC/Pocographite system to 1.26 × 10 10 dyn/ cm 2 in TiN/Inconel system. Both compressive and tensile stresses were found to depend on system. Origins of the residual stress were discussed in relation with difference between thermal expansion coefficients, and also with the fabrication methods.