Characterization and Erosion Behavior of Plasma Sprayed $NiCrAlY$ and $Ni-20Cr$ Coatings on an Fe-based Superalloy

Degradation of materials due to solid particle erosion is encountered in a variety of engineering industries, either at room temperature or elevated temperatures. Nickel-based coatings are commonly used in applications where wear resistance, combined with oxidation or hot corrosion resistance, is required. In the present work, $NiCrAlY$ and $Ni-20Cr$ metallic coatings were deposited on an iron-based superalloy by a shrouded plasma spray process. The coatings were characterized by scanning electron microscopy, optical microscopy, microhardness testing, and x-ray diffractometry. Erosion studies were conducted using an air-jet erosion test rig at a velocity of $40ms−1$ and impingement angles of 30 and $90deg$⁠. Scanning electron microscopy was used to analyze the eroded surfaces. 3D surface roughness profiles of the eroded samples were taken using a Veeco Optical Profilometer. $NiCrAlY$ coatings had slightly lower average porosity and lower microhardness as compared to $Ni-20Cr$ coatings. The observed erosion rate of the $NiCrAlY$ coatings, however was lower than that of the $Ni-20Cr$ coatings at both 30 and $90deg$ impingement angles. $Ni-20Cr$ coating had shown higher erosion rate at $90deg$ impingement angle than that at $30deg$⁠, whereas the effect of impingement angle on the erosion rate is negligible for plasma sprayed $NiCrAlY$ coating. The higher bond strength of $NiCrAlY$ coating might be one of the major contributing factors for lower erosion rate of $NiCrAlY$ coating as compared to $Ni-20Cr$ coating under the tested conditions. Erosion mechanisms of plasma sprayed coatings are discussed.