Sliding wear of various materials in molten zinc

Abstract

A full journal bearing tester was built to study wear behaviour of materials sliding in molten zinc. Various material combinations, including cobalt based superalloys, cermet coatings (on 316L stainless steel substrates), and ceramics were evaluated at conditions similar to continuous galvanising line (CGL) operations. Metallographic and chemical analyses were conducted on tested specimens to characterise the wear. Cobalt based superalloys not only suffered considerable wear but also reacted with molten zinc to form intermetallic compounds. Cermet coatings and ceramics experienced noticeable wear although they were non-wettable and did not react with zinc baths. The study showed that MgO stabilised ZrO₂ suffered the most wear when running against laser clad WC coated 316L while the combination of SiAlON and laser clad WC coated 316L showed the least amount of wear. The composite nature of hard particles imbedded in a soft matrix, posing resistance against both abrasive and surface fatigue wear, is believed to be the reason that laser clad WC coatings can withstand wear in molten zinc.