Faculty Publications
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Item Effect of thermal expansion on the high temperature wear resistance of Ni-20%Cr detonation spray coating on IN718 substrate(Elsevier B.V., 2023) Purushotham, N.; Parthasarathi, N.L.; Babu, P.S.; Govindarajan, G.; Rajasekaran, B.The temperature-dependent materials properties on the dry sliding wear resistance of the detonation sprayed Ni-20%Cr coating have been studied. In-situ high-temperature X-ray diffraction (HT-XRD) was used to investigate high-temperature properties such as stress relieving, recrystallization, and thermal expansion. The dry sliding wear test was performed by using a ball-on-disc tribometer by sliding velocities (0.1 m/s), varying loads (6 N and 10 N), and temperatures (25 °C and 850 °C) against alumina (Al2O3) ball. The phase evolution, thermal expansion, crystallite size, and lattice strain were determined by the Williamson-Hall method. Field emission scanning electron microscopy and a non-contact optical profilometer was used to characterize the wear scar and calculate the wear rate. The wear test results demonstrated that the as-deposited coatings coefficient of friction (CoF) and wear rate (ω) continuously decreased as the temperature increased. The primary wear mechanism changed from abrasive and surface fatigue to adhesive and oxidative wear. The impact of stress relieving, recrystallization, and forming a composite tribolayer (Cr2O3, NiO) at elevated temperatures reduced the friction and enhanced the wear resistance. The effect of stress relieving, recrystallization, thermal expansion, and oxidation on the wear resistance of the coating has been discussed with a suitable mechanism. © 2023 Elsevier B.V.Item The Effect of Detonation Frequency on the Linear Reciprocating Wear Behavior of Detonation Sprayed Ni-20%Cr Coatings at Elevated Temperatures(Springer, 2025) Prasad, R.; Purushotham, N.; Preetham Kumar, G.V.; Babu, P.S.; Govindarajan, G.; Rajasekaran, B.The study explores the impact of detonation frequency (3 and 6 Hz) on the temperature-dependent linear reciprocating wear behavior of Ni-20%Cr coatings deposited by detonation spraying on a nickel-based superalloy (IN718). Dry sliding experiments were carried out at both ambient (25 °C) and high (420 °C) temperatures, using an alumina (Al2O3) ball as the counter material and different loads (5, 10, and 20 N). HV0.2 microhardness indentations were used to test material hardness variations attributed to heat exposure. X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy with energy-dispersive spectroscopy (FESEM with EDS) were used to investigate the wear characteristics and mechanisms. Furthermore, surface roughness and profiles of worn surfaces (including track depth, breadth, and wear volume) enabled the calculation of wear rates using confocal optical 3D profilometry. The results showed the 6 Hz Ni-20%Cr coating showed better wear resistance than the 3 Hz coating. However, a higher wear rate and low friction coefficient at 420 °C were observed due to partial oxide particles, which were insufficient to restrict direct ball-to-metal contact. The research delves into wear maps, tribolayer formation, wear mechanisms, and sub-mechanisms. © ASM International 2024.