Fabrication and characterization of metallic glass coatings by gas flame spraying

Abstract

Nowadays, amorphous state of metallic material can be obtained in many alloys by rapid quenching from the melt condition at a quenching rate more than 10 6K/s. However, in the normal rapid quenching method, amorphous alloys can be formed not as a bulk shape but only as a ribbon or powder shape. On the other hand, in some kind of alloys, amorphous state can be easily given even at a much lower quenching rate like l-100K/s, and it is possible to fabricate bulk shape materials in these alloys. These amorphous alloys are called as a metallic glass. There are several, kinds of manufacturing processes to fabricate the bulk metallic glasses such as an arc melting mixture, copper mold casting and so on. However, especially in an application of metallic glass to the high performance corrosion resistance coating, these processes are hard to apply to real large area coatings on already existing object, surface. Thermal spraying has the advantage of low cost and in-situ formation ability for such large area coatings. Recently, many metallic glasses were developed such as Zr-, Fe- or Ni-based alloy systems. Among these alloy systems, one of the most important alloys can be regarded as Fe-based alloys exhibiting good corrosion resistance. Especially, Fe 43Cr 16Mo 16C 15B 10, alloy are known to have very high, corrosion resistance. In this study, Fe 43Cr 16Mo 16C 15B 10 metallic glass coatings were fabricated by gas flame spraying. Metallic glass coatings were successfully obtained by gas flame spraying by using a reducing flame and water atomized powders. The oxide films which had existed on the feedstock powder surfaces might prevent, the oxidation of the powders during spraying. It was indicated that the gas flame sprayed, particles were once heated over its melting point, and the particles became amorphous state by rapid quenching after the deposition onto the substrate.