Distortion of injection moulded stainless steel compacts during sintering: T. Takekawa (Ishinomaki Sensu University, Ishinomaki, Japan) J. Japan Soc. Powder and Powder Metallurgy, Vol 40, No 5, 1993, 484–487. (In Japanese)

Abstract

Powders of Fe-2.20wt.%C-0.85wt.%Si and Fe-4.16wt.%C-0.87wt.%Si alloys were plasma sprayed on a steel substrate in a low pressure chamber. The deposite layers formed on non-water-cooled substrate are composed of stable phases of ferrite and cementite. When the substrate is water cooled, the main constituents of the deposit layers are retained austenite and a metastable h.c.p. ϵ phase on the free-surface side for the respective alloys, and self-annealing occurs to some extent on the substrate side. On spraying, molten powders solidify at a cooling rate higher than 106 K s−1 in the case of a water-cooled substrate, and the cooling rate is larger than that attained in flame spraying. Such a high cooling rate in low pressure plasma spraying is attributed to the fact that the flattened particles which come from the molten powders to produce a deposit layer are thin and that the heat resistance at the interface between the flattenned particle and the underlying deposit layer is small because of the reduced amounts of pores and oxides at the interface.