Effect of Double-Aging Heat Treatment on Microstructure and Tribological Behaviour of Cold Sprayed IN718 Coating

In this work, the effect of double-aging (DA) heat treatment on the microstructure and the tribological behaviour of cold-sprayed Inconel 718 (IN718) coating was studied and compared with hot-rolled IN718. After double-aging, the dendrite structure of the as-sprayed coating was modified and secondary phases such as γʹ, γʺ, and δ phases were formed. The microhardness of the coating improved after double-aging and was higher than the double-aged IN718 due to the leftover microstrain in the coating. Sliding wear tests were carried out at room temperature (RT) and 600 °C using a ball-on-disc tribometer with alumina balls. The double-aged coating had improved wear resistance than the as-sprayed coating and the double-aged substrate at room temperature. At 600 °C, the wear rate of the hot-rolled IN718 was marginally lower than the as-sprayed coating due to the formation of a comparatively thick mechanically mixed layer (MML) reinforced with Al2O3 which was more protective in nature. The double-aging treatment improved the wear resistance of the coating significantly at 600 °C and its wear rate was comparable to that of the double-aged substrate. The substrate and the coating undergo a combination of abrasive and tribo-oxidative wear at RT. At 600 °C, the wear mechanism involves a combination of oxidative and abrasive modes. Raman analysis revealed that the oxide formed on the wear track consisted of NiO and Fe3O4 at RT, and the glaze layer formed during high-temperature wear consisted of a mixture of the NiFexCr2-xO4 spinel and Fe3O4. Graphical Abstract: [Figure not available: see fulltext.].