Curvature Testing The Residual Stresses In 3%Tio2-Al2o3 Coatings By Thermal Spraying Technology

Plasma thermal spraying technique was adopted to deposit five groups of different thickness 3% TiO2-Al2O3 coatings on 329-Stainless steel. A curvature method was applied to study the residual stresses. Results showed that the deformations corresponding to 3% TiO2-Al2O3/329-SS systems were serious. The residual stress changed with the xi (ratio of coatings' thickness to substrate's thickness) value and weren't constants for the coatings' thickness 52-306 mu m. No regardless of using the Stoney' or Tomanov' formula to calculate the residual stresses, which decreased with the ratio xi value increased, and the thinner coatings were, the greater the residual stresses were. The coatings' residual stresses changed with the xi value at an exponent relation. The coatings' thickness affects greatly on their residual stresses, especially for the intrinsic stresses. When the coatings thickness changes from 52 to 306 mu m, the residual stresses were always compressive stresses. The maximums residual stresses were caused when the xi value is 0.115 (the minimum value), and the details were -584.96 MPa and -482.78 MPa by two difference formulas, respectively.