Thermal-Sprayed Coatings on Bushing and Sleeve-Pipe Surfaces in Continuous Galvanizing Sinking Roller Production Line Applications

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 1 mm 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.

Experimental study of Cu/Fe underwater self-constrained explosive welding tube

“…Mechanically bonded is less expensive and has a wider range of applications, but has lower strength relative to metallurgical bonding and the mechanically bonded seam is a weak site for corrosion [20]. Owing to the large difference in physical properties between the base tube and the inner tube, some coatings prepared by many coating technologies have poor adhesion to the steel substrate, and problems such as cracking and low corrosion resistance are prone to occur after welding [21, 22]. Moreover, the conventional explosive welding process is easy to cause serious distortion or even fracture of the composite pipe [23].…”

Effect of Tip Shape of Frictional Stir Burnishing Tool on Processed Layer’s Hardness, Residual Stress and Surface Roughness

“…These methods are used for auto parts and various kinds of mechanical parts. On the other hand, thermal-sprayed coatings [8] or blasting process [9] can make additional layers using different material from the base metal to get higher hardness, wear resistance, thermal resistance, or corrosion resistance.…”