Abstract
The effects of coating configurations and hot-pressed strengthening treatment on the properties of ceramic-metal composite coatings were investigated. Alumina and Ni-base self fluxing alloy were plasma sprayed onto mild steel using recommended spray conditions for alumina. Hot-pressed treatments were carried out in vacuum. The adhesive strength of the coatings under static loading and the repeated thermal shock resistance were tested as well as the abrasive wear and electrochemical corrosion resistance. The porosity, coating thickness and microhardness were also measured.
The results obtained are summarized as follows:
1) The mixed coatings were superior in wear resistance, whereas the composite coating proved to be more resistant to repeated thermal shock and corrosion.
2) Hot-pressed treatment showed excellent effects on the coatings properties. It tightened the substrate/coatnig interface which resulted in higher adhesive strength, and it also made the coatings to be denser. The mixed coatings showed improvements in their wear and thermal shock resistance, corrosion and thermal shock resistance were, on the other hand, improved in the case of composite coatings. However, over a certain hot-pressed treatment temperature, the composite coatings performance was reduced.
