Manufacture of a cermet/ceramic coated steel plate by a combined plasma spraying and hot rolling method

In this study we propose a plasma spraying technique which is combined with the continuous hot rolling method to realize not only an inexpensive but also a high productivity manufacturing process of steel plates coated with high grade materials (among them are cermets and ceramics) and having good adhesion between the coating and the steel substrate. This study also aims at investigationg the best suited combination of working parameters to demonstrate the feasibility of this process.

More specifically, coated steel plates with two kinds of coating materials are made with this technique; first WC-Co coating (a cermet coating) is tried aiming at good wear resistance and then a Y₂O₃ stabilized ZrO₂ coating ( a ceramic coating ) having Ni-Cr alloy as an undercoat is tried to realize a thermal barrier means and/or an anti-corrosive means at high temperatures. Then several factors governing this technique, i.e., coating thickness, rolling reduction rate and heating temperature ( for hot rolling ) are investigated in order to manufacture the coated steel plate having sound cermet or ceramic top surface.

The results are that it is possible to manufacture coated steel plates having a better adhesive strength between the coating and the substrate as compared with an as-sprayed coating by selecting a coating thickness of 100–160 μm, a rolling reduction rate of below 3% and a heating temperature of 600°C in the case of WC-Co coating and 1100°C in the case of ZrO₂ coating respectively.