Abstract
This paper describes thermal spray techniques for making hard coatings on bushing and sleeve component surfaces. Specifically, plasma-arc welding was used to produce 5-mm thick Co-Cr alloy welding overlays on the bushing, while a high-velocity oxy-fuel spraying technique and laser re-melting technique were used to produce thinner coatings of Co-Cr-Ni+WC of about 1mm thickness on the sleeve-pipe counterparts. The surface-treated components were then submerged in liquid zinc to study the corrosive behaviour of the surface coating and substrate. Both the scanning electron microscope and energy dispersive spectrometer analyses were used to study the microstructure and phase composition of both coatings and substrates prior to and after corrosion experiments. The results show that the microstructure of the bushing consists of γ-cobalt solid solution as well as the eutectic structure of γ-cobalt and carbides, which have good corrosive resistance against molten zinc. Meanwhile, the microstructure of the sleeve pipe consists of a Co-Cr solid solution with various forms of carbides, which displays the combined properties of toughness with good corrosive resistance to molten zinc.
Highlights
In the continuous galvanised zinc (Zn)-coating production lines in typical manufacturing factories, the rollers consist of sink rollers and tension rollers
Sink rollers are submerged in molten Zn baths and are subject to high-temperature corrosion in Zn solutions and continuous wear of the steel strip
Bushings and sleeve pipes are the main components on the sink-roller assembly, which are used as supports and rotation pairs for the sink rollers
Summary
In the continuous galvanised zinc (Zn)-coating production lines in typical manufacturing factories, the rollers consist of sink rollers and tension rollers. To improve the service life of(Cr) bushings and sleeve pipes as well as toor reduce losses, includes high nickel (Ni)-chromium stainless steel, Ni-based alloys cobalteconomic (Co)-based alloys many methods had been chosen to improve their wear resistance and anti‐corrosion, such as selecting for creation, but it obviously leads to higher manufacturing costs [10,11,12,13]. The choice of materials surface infiltration and centrifugal casting for the preparation of the bushings and sleeve pipes with usually includes high nickel (Ni)‐chromium (Cr) stainless steel, Ni‐based alloys or cobalt (Co)‐based a composite structure a way to reduce thetoproduction cost and maintain excellent performance, alloys for creation,isbut it obviously leads higher manufacturing costs [10,11,12,13]. It includes the surface properties of the coatings associated with their performance in a molten Zn work environment
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