Neutron diffraction residual strain measurements in alumina coatings deposited via APS and HVOF techniques

Residual strains in air plasma sprayed (APS) and high velocity oxy-fuel (HVOF) alumina (Al₂O₃) coatings were investigated by means of neutron diffraction technique. Results of this investigation conclude that through thickness residual strain in the APS coating was mainly tensile whereas the HVOF coating had both compressive and tensile residual strain. Further analysis of Vickers indentation fracture behaviour using acoustic emission (AE) technique concluded that the nature and magnitude of these residual strain fields had a direct effect on the fracture response of two coatings during the indentation process.