Composite Coatings of Alumina-based Ceramics and Stainless Steel Manufactured by Plasma Spraying

Abstract

Plasma spraying was used to fabricate composite (cermet) coatings from a mixture of powders of alumina-based ceramics and stainless steel. Regarding the water-stabilized plasma spray process (WSP), the two powders were mixed in the feed container, whereas a simultaneous feeding of the powders by separate injectors (co-spraying) was carried out together with the gas-stabilized plasma spray process (GSP). Both processes belong to a family of procedures known as atmospheric plasma spraying (APS), and give rise to similar coating characteristics. The complementarity of the component mixing in the two processes was demonstrated, and the mechanical properties such as microhardness and elastic modulus of the resulting composite coatings were studied. Attention was also paid to microstructural aspects connected to wear resistance.
WSP spraying of the mixed powders resulted in coatings composed of successive layers of ceramics and stainless steel, in which the relative thickness varied with the steel content. The GSP-produced cermet coating exhibited microstructures without microcracks or interconnected porosity, and such structures gave rise to good mechanical properties with respect to elastic modulus, hardness and wear resistance.