Development of Plasma Spray Coatings Using Linz-Donawitz (LD) Slag Particles

LD slag (LDS) is a major solid waste generated in huge quantities during steel making. It comes from slag formers such as burned lime/dolomite and from oxidising of silica, iron etc., while refining the iron into steel in the LD furnace. This work aims at utilization of waste LDS to develop surface coatings by plasma spraying technique. This technology has the advantage of being able to process various low-grade ore minerals to obtain value-added products and also to deposit materials, generating near homogeneous coatings with the desired microstructure. Coatings prepared for this investigation are characterized in terms of their thickness, hardness, adhesion strength and porosity. Coating deposition efficiency is calculated in order to assess the coatability of LDS and XRD is carried out in order to ascertain the various phases present in the coating. Premixing of TiO₂ powder with LDS is found to substantially improve the interfacial adhesion. It is also found that the operating power levels of the plasma torch affect the adhesion strength, coating deposition efficiency and mean thickness of the coatings. This work reveals that LD slag is eminently coatable and can be gainfully used as a potential cost-effective material for deposition of plasma spray coatings on metallic substrates.