Abstract
Fly-ash premixed with quartz and illmenite powder in different weight proportions are thermal sprayed on mild steel and copper substrates at various input power levels of the plasma torch ranging from 11 kW to 21 kW DC. The erosion test has done using Air Jet erosion test Reg (As per ASTM G76) with silica erodent typically 150-250 pm in size. Multiple tests were performed at increasing the time duration from 60 sec to 180 sec with increasing pressure (from 1 bar to 2.5 bar) and angle (60° & 90°). This study reveals that the impact velocity and impact angle are two most significant parameters among various factors influencing the wear rate of these coatings. The mechanisms and microstructural changes that arise during erosion wear are studied by using SEM. It is found that, when erodent are impacting the fresh un-eroded surface, material removal occurs by the continuous evolution of craters on the surface. Upper layer splats are removed out after 60 sec and second layer splat erosion starts. Based on these observations Physical models are developed. Some graphs plotted between mass loss-rate versus time period/impact Pressure/impact Angle gives good correlation with surface features observed.
Highlights
Solid particle erosion is to be expected whenever hard particles are entrained in a gas or liquid medium impinging on a solid at any significant velocity
Initial piled up material is heavily strained and some small cracks are observed & spread along splats boundaries. This is the reason of fragmentation of splat during solid particle erosion
The flyash+quartz+illmenite coating gives much harder than substrate metals for which it can be recommended for tribological applications
Summary
Solid particle erosion is to be expected whenever hard particles are entrained in a gas or liquid medium impinging on a solid at any significant velocity. In the automotive industries of many advanced countries, plasma-sprayed coatings are used to improve the resistance to erosion, abrasion and corrosion of machine components and structural parts [8]. This spray technology has the advantage of being able to process various low-grade minerals to obtain value-added products and to deposit ceramics, metals, and even a combination of these, generating near-homogenous composite coatings with the desired microstructure on a range of substrates [9,10,11]. Challenges related to thermal spray process concerning the improvement of spray systems and spraying of new materials. These aspects require a better understanding of the involved phenomena, i.e., physical, chemical, thermodynamics, etc. to improve the efficiency of plasma spray coating operation [12,13,14,15]
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