The Effect of Temperature-Dependent Properties on The High Temperature Sliding Wear Behaviour of Detonation Sprayed Ni-Based Coatings
Date
2023
Authors
N., Purushotham
Journal Title
Journal ISSN
Volume Title
Publisher
National Institute Of Technology Karnataka Surathkal
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.