Residual Stress Measurement of Plasma-Sprayed Coatings

Residual stresses of plasma sprayed coatings, NiCr alloy, CoNiCrAlY alloy, Al₂O₃ ceramics and ZrO₂-8%Y₂O₃ ceramics, were measured in this study. SACHS method with a strain gauge was used to measure the residual stress. Type 304 stainless steel and mild steel were selected for the substrates. The results obtained were summarized as follows: 1) Tensile residual stresses were generated in plasma sprayed coatings. 2) The values of residual stress in ceramics coatings were relatively small and the values took lower than 40MPa. 3) Tensile residual stress values of metallic alloy coatings on mild steel substrates were higher than those on type 304 stainless steel substrates. 4) Residual stresses in Low Pressure Plasma Sprayed (LPPS)-coatings were larger than those in Atmospheric Plasma Sprayed (APS)-coatings. 5) Pre-heating of a substrate will effectively reduce tensile residual stress in a coating.