Method of forming carbide-base composite coatings, the composite coatings formed by that method, and members having thermally sprayed chromium carbide coatings

摘要

Thermally sprayed coatings made from carbides of metals having greater carbon affinity than Cr in the presence of free carbon, or thermally sprayed coatings made from carbides of metals having smaller carbon affinity than Cr are heat treated in a chromium halide containing atmosphere which also contains hydrogen gas, whereby activated metallic Cr is precipitated in a fine particulate form, which is allowed to act on the thermally sprayed coatings, whereupon a Cr23C6-form carbide is created not only on the coating surface but also in its interior, particularly within pores, to form a modified layer, thereby compositing the thermally sprayed coatings. Members coated with thermally sprayed Cr3C2, Cr7C2 coatings or thermally sprayed chromium carbide coatings further containing free carbon or carbides of metals having smaller carbon affinity than Cr are heat treated in a chromium halide generating atmosphere which also contains hydrogen gas, whereby activated metallic Cr is precipitated in a fine particulate form, which is allowed to act on the thermally sprayed coatings, whereupon a Cr23C6-form carbide is created not only on the coatings surface but also in its interior, particularly within pores, to form modified, thermally sprayed chromium carbide coatings.