Thermal and mechanical properties of high velocity oxygen fuel sprayed MCrAlY coatings
Itoh Yoshiyasu; Saitoh Masahiro; Takahashi Masashi
Abstract:The high velocity oxygen fuel (HVOF) system in air has been established for producing various coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Ni,Co or Fe) coating can be applied to protect the oxidation and corrosion in the hot section of gas turbines. Also, it is well known that thicker coating can be sprayed by this system for improving the residual stress in comparison with any other thermal spraying system. However, the mechanical properties of HVOF coating have not always been clarified. In this paper, the mechanical properties were measured in order to compare with a low pressure plasma sprayed MCrAlY coating. In case of the as sprayed coating, the Young's modulus and bending strength of HVOF MCrAlY coating were inferior in comparison with those the low pressure plasma sprayed MCrAlY coating. However,the experimental results suggest that the strength of HVOF MCrAlY coating can be improved by a diffusion heat treatment. These phenomena may be attributed to the fact that the HVOF MCrAlY coating is built up by semi fused sprayed particles. Key Words:high-velocity oxygen-fuel (HOVF) system, MCrAlY coatings, Young's modulus, bending strength, hardness