DEVELOPMENT AND PERFORMANCE ANALYSIS OF Ni–15Cr2O3–5TiO2 AND Ni–15Al2O3–5TiO2 HVOF COATINGS IN EROSIVE FLY ASH SLURRY

This study is focused on improving the mechanical properties and slurry erosion resistance of traditional Ni–20Al2O3 and Ni–20Cr2O3 thermal spray coatings by reducing the 5% of Al2O3 and Cr2O3, respectively, and addition of 5% TiO2 feedstock in both coatings. Thermal sprayed powders were thermally sprayed on SS-420 substrates with high-velocity oxy-fuel (HVOF) method. A lab-scale pot tester was used to conduct the wear testing at low rotating speeds of 750, 1000, 1250, and 1500 rpm. To create severe accelerated conditions, a high mass flux (35–50 wt.%) of fly ash particles was used. Multi-sized fly ash slurries ranging from <53 μm to 250 μm were used during the experiments to evaluate the impact of particle size fraction on the erosion over a 30–120 min time-period. Coatings’ surface characterization was done to examine more about their composition. According to the findings, the addition of 5% TiO2 powder to both Ni–15%Al2O3 and Ni–15%Cr2O3 coatings significantly improved their wear resistance of SS-420. This occurred because of the enhancement of hardness as well as brittleness by 5% TiO2 in matrix of Ni–15%Cr2O3 and Ni–15%Al2O3 coatings. Moreover, TiO2 particles aid in strengthening of Cr2O3 and Al2O3 reinforcements and the binding with matrix. Also, the results showed that Ni–15Cr2O3–5TiO2 coating showed superior wear resistance compared to Ni–15Al2O3–5TiO2 coating.