| Most corrosion resistant steel products of the world should be Hot-Dip galvanizing currently. Hot-galvanize has become the most basic and widely used method in steel corrosion resistant. At the operating temperatures for hot-galvanization (450℃~480℃), the dissolving corrosion between melting zinc and steel often happens, which causes quick leakage of the hot-galvanizing tank and becomes one of the most troublesome problems in the field of hot-galvanization. The frequency of replacement or repair the sink roll brings about a lot inconveniences to production and operation, resulting in the greatly consumption of zinc, and not only reduces the operating rate, but also increases the labor intensity.The thesis has study the metallographic appearance,porosity,adhesive strength,hardness,corrosion resistance to liquid zinc and resistance to thermal shocks of hot-galvanize rolls` coating prepared by three kinds of Co/WC powder. Finding the coatings are composed of Co base metal and WC hard phase, the porosity of coating close to 2%.During the test of corroding by liquid zinc, the coating prepared by WC-12Co which spheroidizing better performance best. The SEM,EDS,XRD shows that the WC has no tissue changes, but phase change of base metal causes the failure of coating. Corrosion products of base metal causes the transversal crack which lead to the coating out of protect. Co-Cr-WC coating breakdown after the twenty ninth thermal shock, it could be observed by SEM that the high temperature toughness of coating is not good, the coating is peeling off after thermal shock repeat.According to the dissertation,the powder which spheroidizing better shows the best over-all properties. |
PDF Full Text Request