Agglomerated anti-friction granules for plasma deposition

Reference Number: N 01-02

Inventors: Rao, V. Durga Nageswar

Owner: NISTAC

USPTO Link: 5846289

Invention Summary

In a first aspect, it is an object of this invention to provide a corrosion resistant metal powder useful for plasma deposition of a coating that (i) will possess a low dry coefficient of friction (i.e. about 0.30) and (ii) will readily conduct heat through the coating. To this end, the invention is a collection of agglomerated anti-friction grains for plasma deposition, the grains each consisting essentially of (a) H.sub.2 O atomized stainless steel particles, (b) solid lubricant particles consisting of at least one of boron nitride or a eutectic of calcium fluoride and lithium fluoride, and (c) a binder holding said steel and solid lubricant particles together for plasma spraying, said binder being present in an amount of 0.5-4.0% by weight and is vaporizable at the temperature of plasma spraying and does not interfere with the deposition process.

In a second aspect, it is an object of this invention to provide a method of making agglomerated air-hardenable anti-friction grains useful in plasma spraying that (i) is highly economical, (ii) has a noncrushable strength in the powder form, and (iii) promotes fine flowable particles. To this end, the invention is a method of making agglomerated grains of powder suitable for plasma deposition, comprising the steps of (a) H.sub.2 O atomization of a molten stream of martensitic stainless steel to produce a collection of comminuted first particles, (b) uniformly blending such first particles with solid lubricant second particles and a binder agent in an aqueous slurry, the binder agent being present in a small amount and being constituted to vaporize at the temperature of plasma spraying, and (c) mist spraying the slurry into a heated chamber to form a collection of porous rounded granules