Method of making powder for thermal spray application

Abstract

A method is disclosed for preparing an intimate mixture of powders of nickel-chromium-boron-silicon alloy, molybdenum metal powder, and Cr.sub.3 C.sub.2 /NiCr alloy suitable for thermal spray coatings which comprises milling a starting mixture of the above two alloys with molybdenum powder to produce a milled mixture wherein the average particle size is less than about 10 micrometers in diameter, forming an aqueous slurry of the resulting milled mixture and a binder which can be an ammoniacal molybdate compound or polyvinyl alcohol, and agglomerating the milled mixture and binder. The intimate mixture and binder may be sintered in a reducing atmosphere at a temperature of about 800.degree. C. to 950.degree. C. for a sufficient time to form a sintered partially alloyed mixture wherein the bulk density is greater than about 1.2 g/cc. The resulting sintered mixture may be entrained in an inert carrier gas, passed into a plasma flame wherein the plasma gas can be argon or a mixture of argon and hydrogen, and maintained in the plasma flame for a sufficient time to melt essentially all of the powder particles of the sintered mixture to form spherical particles of the melted portion, and to further alloy the sintered mixture, and cooled.