The Effect of Temperature-Dependent Properties on The High Temperature Sliding Wear Behaviour of Detonation Sprayed Ni-Based Coatings

Abstract

Overlay Ni-based thermal spray coatings are commonly used in high- temperature sectors (up to 1000 ˚C) to enhance component durability for various applications. The Ni-based overlay coatings, such as Ni-5%Al and Ni-20% Cr, were deposited on the IN718 substrate using detonation spray coating (DSC) with a thickness of about 250±25 μm. The temperature-dependent material properties such as thermal expansion, recrystallization, and stress relieving of the coatings on the high-temperature wear resistance 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 (CTEs). The dry sliding friction and wear test was performed by using a ball-on-disc tribometer by sliding velocities (0.1 m/s), varying loads (6N and 10N), and temperatures (25 ˚C and 850 ˚C) against alumina (Al2O3) counterpart. The Rietveld refinement method was used to calculate phase quantification, crystal orientation, and peak fitting employing pseudo voigt analytical functions with the Panalytical X'pert high plus software. The crystallite size (D) and lattice strain (ε) were determined by the Scherrer equation and Williamson-Hall (W-H) analysis using a uniform deformation model (UDM), employing X-ray peak profile analysis (XPPA). Field emission scanning electron microscopy (FE-SEM) with Energy-dispersive X-ray spectroscopy (EDS) was used to analyze surface morphology, cross-section, and wear maps and identify wear mechanisms and elemental composition at different conditions. A confocal optical microscope 3D profilometer was used to measure the surface roughness, depth, and width of the wear scar and further to calculate the wear volume and wear rate. Raman spectroscopy was also employed to determine the chemical phase compositional alterations by analyzing the worn surfaces of the coatings at elevated temperatures. Glow Discharge Optical Emission Spectrometry (GD-OES) was used to measure the quantitative depth profiles with different chemical compositions and the thickness of reaction zones. The wear test results demonstrated that the as-deposited Ni-based coatings coefficient of friction (CoF) and wear rate (ω) continuously decreased as the temperature increased. The primary wear mechanism changed from abrasive (micro- iploughing) and surface fatigue (delamination) to adhesive (material transfer) and oxidative wear (Tribo-oxidation). The impact of stress relieving, recrystallization, and forming a composite tribo-layer (Cr2O3, NiO) at elevated temperatures reduced the friction and enhanced the wear resistance. In high-temperature conditions, the thermal expansion mismatch between the coating and substrate is negligible, with reduced spallation and cracking at the interface. The effect of stress relieving, recrystallization, thermal expansion, and oxidation on the wear resistance of the coating has been discussed with suitable wear mechanisms for improving the tribological properties at high temperatures.