Measurement of Residual Stress in Plasma-Sprayed Composite Coatings with Graded and Uniform Compositions

摘要

Residual stresses in plasma sprayed composite coatingswere studied experimentally by both curvature and neutrondiffraction measurements. Graded and uniform composite coatings,consisting of nickel + alumina and NiCrAlY + yttria-stabilizedzirconia, were investigated. This paper briefly summarizes ourrecent work dealing with the effects of coating thickness,composition, and material properties on the evolution of residualstresses in coatings. Analysis of the results allowed in some casesthe separation of the quenching stress and thermal stresscontributions to the final residual stress, as well as thedetermination of the through-thickness stress profile frommeasurements of different thickness specimens. In the ceramic-metal composites, it was found that the thermal mismatch stressplays a dominant role in the ceramic phase, whereas the stress inthe metallic phase is mostly dominated by quenching stress. Theresidual stress measurement methods employed here were found to becomplementary, in that each can provide unique information aboutthe stress state. Through-thickness stress profiles in gradedcoatings were determined with high spatial resolution by thecurvature method, and determination of the stress in each separatephase of a composite was made by neutron diffraction.