Industrial Lubrication and Tribology

Purpose – The paper's aim is to investigate the sand slurry erosive wear behaviour of Ni-Cr-Si-B coating deposited on mild steel by flame spraying process under different test conditions.

Design/methodology/approach – Flame sprayed coatings of Ni-Cr-Si-B were developed on mild steel substrate The slurry pot tester was used to evaluate wear behaviour of the coating and mild steel. The erosive wear test was conducted using 20 and 40 per cent silica sand slurry at three rotational speeds (600, 800 and 1,000?rpm).

Findings – Slurry erosive wear of the coating showed that in case of 20 per cent silica sand slurry weight loss increases with increase in rotational speed from 600 to 1,000?rpm while in case of 40 per cent silica sand slurry weight loss first increases with increase in rotational speed from 600 to 800?rpm followed by marginal decrease in weight loss with further increase in rotational speed from 800 to 1,000?rpm. Increase in wear resistance due to thermal spray coating of Ni base alloy on mild steel was quantified as wear ratio (weight loss of mild steel and that of coating under identical erosion test conditions). Wear ratio for Ni-Cr-Si-B coating was found in range of 1.4-2.8 under different test conditions. The microstructure and microhardness study of coating has been reported and attempts have been to discuss wear behaviour in light of microstructure and microhardness. Scanning electron microscope (SEM) study of wear surface showed that loss of material from the coating surface takes place by indentation, crater formation and lip formation and its fracture.

Practical implications – It would assist in estimating the erosion wear performance of flame sprayed Ni-Cr coatings and their affects of wear resistance.

Originality/value – Erosion wear of flame sprayed coatings in sand slurry media medium is substantiated by extensive SEM study.