Quenching, thermal and residual stress in plasma sprayed deposits: NiCrAlY and YSZ coatings

Residual stress is an important factor in thermally sprayed deposits which affects both processing and performance. High stress magnitudes and/or concentrations can undermine the structural integrity of sprayed parts and impair their functionality. Therefore, it is important to know the stress state, understand its generation and be able to control it. Results of experimental stress determination in plasma sprayed deposits are presented. Neutron diffraction as a non-destructive and phase-distinctive measurement method was used to determine residual stress profiles in thick NiCrAlY and yttria-stabilized zirconia (YSZ) deposits. Measurements were complemented with calculations based on experimentally determined material properties, which allowed for separation of quenching and thermal stress contributions to final residual stress. Since the application of neutron diffraction to plasma sprayed deposits is relatively novel, certain verification measurements were performed. Specimens were prepared at two different deposition temperatures, to determine the effect of temperature on the stresses and relevant deposit properties.