Non-Linear Mechanical Behavior of Plasma Sprayed Alumina Under Mechanical and Thermal Loading

Mechanical response of plasma sprayed ceramic coatings to mechanical and thermal loading of various extents was studied. Coated samples were subjected to four-point bending (4PB), with coatings loaded in tension and compression, respectively. Thermal loading was provided by heating the samples, while stresses were generated by thermal mismatch between the coatings and substrates. In both cases, cyclic loading was applied. Non-linear behavior and significant hysteresis were observed, indicating inelastic phenomena taking place. The tests were complemented by structural observations in SEM and indentation tests. Relevant structural features and possible mechanisms underlying this behavior are discussed.