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The solid-particle erosion of metals and alloys at elevated temperatures is characterized by different mechanisms of material removal, depending on the temperature of exposure, impact velocity, impact angle, and flux rate of the eroding particles. The objective of this article is to delineate the prevalent erosion mechanisms in nickel and a nickel-20 chromium alloy over a large range of temperatures, impact velocities, impact angles, and particle feed rates. For this purpose, a specialized elevatedtemperature erosion rig has been utilized. Nickel and a Ni-20Cr alloy have been chosen as the test materials, in view of their substantially different oxidation behaviors. Results from the present study indicate that while the erosion rate generally increases with increasing temperature, an increased particle feed rate causes a reduction in the erosion rate, especially at higher temperatures beyond 650 K. On the basis of a detailed examination of the morphology of the eroded surfaces and the subsurface features beneath the eroded surfaces, four different material removal mechanisms have been identified in the nickel, while only three material removal mechanisms were operative in the Ni-20Cr alloy. Utilizing the aforementioned information, erosion-oxidation (E-O) interaction mechanism maps (herein, termed E-O maps) delineating the regions of dominance of the various erosion mechanisms in an impact velocity-test temperature space have been constructed for Ni and a Ni-20Cr alloy. Finally, the differences in erosion behavior between the Ni and Ni-20Cr alloy have been identified and rationalized.

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The main objective of this work is to examine the feasibility of depositing aluminum nitride (AlN) powders, synthesized using self-propagating high-temperature synthesis, on a mild steel substrate using the detonation spray coating technique. Thick coatings produced by utilizing the AlN powder were obtained at four different oxygen–acetylene ratios and analyzed for microstructure, microhardness, porosity, indentation fracture toughness, and phase distribution. The AlN powder particles were found to be undergoing oxidation during the deposition process. The interrelationship between the spray parameters and the extent of oxidation of AlN during the coating process was investigated. Tribological performance of the coatings was evaluated using a dry sand abrasion test and a pin-on-disc sliding wear test. The mechanical and tribological properties of the above four coatings were compared with pure alumina (Al2O3) coatings. The correlation between the structure of the coatings and their tribological performance was also established.

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