Abstract
The composition of nickel-based metal matrix NiCrBSi was varied with 5%, 10% and 15% of Al2O3 particles to obtain high wear resistant coatings by means of a high-velocity oxy fuel (HVOF) thermal spraying process. The coating was characterized by optical microscope, scanning electron microscope (SEM) and X-ray diffractometer (XRD). The physical properties of coatings such as porosity, thickness, surface roughness, surface hardness, fracture toughness, bond strength and density were measured and compared. The experimental design of Taguchi L27 orthogonal array was employed to study and compare the effect of parameters such as impingement angle, impact velocity and alumina per cent in the coating on erosion. The coating containing 15 wt.% of Al2O3 and erodent speed of 33 m/s striking at inclination angle of 30° proved to be the best arrangement in preventing volume loss to a minimum of 0.00015 cc due to low-impact energy, high bond strength and high surface hardness. Analysis of variance (ANOVA) supported the assertion that the impact angle (A) of erodent and composition (C) were the factors contributing most to the volumetric loss as indicated by their combined effect A × C leading to the highest combined factor of 7.34. The scanning electron microscopy (SEM) images of the eroded coatings reveal that the mechanisms of erosion were the fracturing of splats, development of craters, micro cutting and ploughing action.
Highlights
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In order to improve the wear and corrosion resistance of the coatings, materials like Ni, Co, Ti, and W-based alloys and ceramics are commonly used as coating materials [9,10,11]
Many researchers have reported on the tribological properties of the Ni-based coatings and stated that these coatings improve the wear and corrosion resistance of surfaces [12,13,14,15,16]
Summary
The thermal spraying method of coating on the surface is one of the methods of reducing material retrogradation process, governed by melting temperature of the coating material; the flame temperature; the gas pressure; the coating material progressive or movement speed rate; the shape of the nozzle employed; the spray distance; the surface preparation of the substrate material etc. [1,2,3,4].The high-velocity oxy fuel (HVOF) procedure involves low expenditure, high flexibility and low coating thickness in the range of a few hundreds of micrometers [5,6,7,8].
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