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 Al 2 O 3 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 Fe 3 O 4 at RT, and the glaze layer formed during high-temperature wear consisted of a mixture of the NiFe x Cr 2-x O 4 spinel and Fe 3 O 4 . Graphical Abstract