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This paper investigated the solid particle erosion behavior of partially oxidized NiCrBSiFe and NiCr coatings by varying temperature and impact angle. The challenge in the current situation is to process a new system of powders containing metallic and oxide phases. Partially oxidized powders containing metallic and oxide phases were processed by flame spraying the alloy powders into distilled water and allowing the oxide layer to form while keeping the core in the middle of the particle. Partially oxidized coatings were developed on MDN321 steel using the plasma spray technique with feedstock of partially oxidized powders. An air jet erosion test was carried out using Al2O3 erodent of grit size 50 µm at room temperature, 200, 400, 600, and 800°C by varying 30, 45, 60, 75, and 90° impact angles. Coatings were characterized concerning bond strength, porosity, micro-hardness, and density. The effect of temperature and impact angle on volumetric erosion loss was studied using SEM, EDS, and XRD analysis. Partially oxidized NiCrBSiFe coating exhibited better erosion resistance compare with partially oxidized NiCr coating. NiCr coating demonstrates maximum volumetric erosion loss at 45° impact angle, whereas NiCrBSiFe at 60° impact angle under all tested temperatures. [ABSTRACT FROM AUTHOR]

The present research aims to investigate the effect of different impact angles and temperatures on volumetric erosion loss of WC-Co-Cr coating containing 10 wt% Mo. The composite coating was developed using High-Velocity Oxy Fuel (HVOF) process on a titanium substrate (Ti-31). A solid particle erosion behavior of the coatings is carried out at different impact angles (30°, 60°, and 90°) and temperatures (200 °C, 400 °C,600 °C, and 800 °C). The volumetric erosion loss of the coated samples was measured using an air jet erosion tester at high temperatures using Al 2 O 3 as an erodent. The XRD, SEM/EDS, porosity, density, microhardness, bond strength, and scratch tests characterized the as-sprayed coatings. The 3D optical profilometer was employed to evaluate the volumetric erosion loss and the mode of erosion. The scratch resistance of WC-Co-Cr coating is better than WC-Co-Cr/Mo coating. The WC-Co-Cr coating shows a brittle mode of erosion up to 600 °C and a ductile mode of erosion at 800 °C. In contrast, the WC-Co-Cr/Mo coating shows a brittle mode of erosion at 200 °C and a mixed mode of erosion at 400 °C to 800 °C. The volumetric erosion loss of WC-Co-Cr is less than WC-Co-Cr/Mo for all temperatures and impact angles. The formation of oxide phases on the coating surfaces demonstrates erosion resistance at high temperatures. The results of volumetric erosion loss measured by the weight loss method correlate well with a non-contact type 3D optical profilometer. • The scratch resistance of WC-Co-Cr is higher than WC-Co-Cr/Mo. • The formation of oxide phases causes the WC-Co-Cr coating to change from brittle to ductile erosion mode at 800 °C. • Adding Mo, the coating shifts the mixed mode of erosion from 600 to 800 °C. • The volumetric erosion loss of WC-Co-Cr is less than WC-Co-Cr/Mo coating for all temperatures and impact angles. • Oxide phases increase the erosion resistance of coating at high temperatures. [ABSTRACT FROM AUTHOR]

The powders of NiCrBSiFe and NiCr are partially oxidized using a flame spray process and are deposited on MDN321 steel substrate using a plasma spray process. The effect of partial oxidization on microstructure, microhardness, density, bond strength, and porosity of the coatings is analyzed. The friction and wear behaviour of the coatings was assessed using a pin-on-disc tribometer by varying loads (10, 20 and 30 N), sliding velocities (1, 2 m/s) and temperatures (RT, 200, 400 and 600 °C). Worn surfaces of NiCrBSiFe and NiCr coatings consist of oxide phases of SiO 2 , NiO, Cr 2 O 3 and NiCr 2 O 4 at elevated temperatures. These phases contributed to reducing the wear rate by five folds in coated steels compared to uncoated steels at 600 °C. The wear rate in coating decreases with an increase in temperature. The coefficient of friction was reduced gradually with the temperature in coatings and substrate. The wear rate coefficient of NiCr coating was 1.7 times higher than the NiCrBSiFe coating. [Display omitted] • Partially oxidized coatings were developed by combined technique of flame and plasma spray. • Wear and frictional behaviour of coatings at elevated temperature were analyzed. • Wear rate coefficient of the partially oxidized coating is better than MDN321 steel. • Friction coefficient reduced with increase in temperature, load and sliding velocity. [ABSTRACT FROM AUTHOR]