Residual Stress Study of Nickel Aluminide (βNiAl) Coatings Deposited by In Situ Chemical Vapour Deposition Method

Abstract

Nickel aluminide (βNiAl) is a bond coat material used in thermal barrier coating (TBC) system of aeroengines. The performance of TBC is significantly influenced by the thermal response of bond coat (BC) material. Usually, the most failures of the TBCs are attributed to poor performance of a BC. There are several factors that affects the performance, such as; oxidation, mechanical damages, manufacturing oriented problems (thermal residual stresses) etc. In this study, βNiAl was deposited onto CMSX-4 superalloy substrates using in-situ chemical vapour deposition (CVD) method. Zirconium was also incorporated as a dopant into βNiAl coating. Residual stresses were measured using X-ray diffraction (XRD) method. In particular, the comparison was made between the doped and undoped coating samples. Results demonstrated minimum thermal stresses in the zirconium doped coating in comparison to its undoped counterpart. Possible mechanism of stress removal is discussed.