Reproducibility in production of coatings has always been a concern in plasma spraying. In this study, the comparison of the stress and strain behavior of coatings produced under several conditions: same batch, daily production, active control of particle state by diagnostics sensors, is presented. Special attention is given to the degree of non-linearity and hysteresis of ceramic coatings during thermal loading.
For analysis and comparison, three different materials (YSZ-Hollow-oven spherical powder, YSZ-Fused and crushed powder, and TiO₂ powder) were sprayed via air plasma spraying on aluminum 6061 substrates. The curvature change during the post deposition low temperature heat cycling is measured and the corresponding curvature-temperature data is converted to stress-strain curve using proper formulas.
The reproducibility of these coatings, hence the repeatability of the spray process is discussed in terms of coating thickness, residual stress, particle state control and non-linear elastic behavior.