Characterisation and erosion behaviour of a plasma sprayed Ni3Al coating on a Fe-based superalloy

In the present investigation plasma spray metallic coating of nickel-aluminide was deposited on a Fe-based Superalloy (32Ni-21Cr-1.5Mn-1Si-0.3Ti-0.3Al-0.1C and Balance Fe) by shrouded plasma spray process. NiCrAlY was used as a bond coat. Erosion studies were conducted, using an air-jet erosion test rig at a velocity of 40 m/s and impingement angles of 30° and 90°, on uncoated as well as plasma spray coated superalloy specimens at room temperature. Silica sand particles of size ranging between 150 and 212 μm were used as erodent. The coating has been characterised for porosity, microhardness, microstructure and X-ray diffraction (XRD). Scanning electron microscopy (SEM) technique was used to analyse the eroded surfaces. Erosion behaviour of the coating and superalloy is discussed. Erosion rate of the coating was found marginally higher than the superalloy at both the impact angles. Possible erosion mechanisms are discussed.