Abstract
Some metallurgical studies were made on 15/17% Cr-Ni steel powder compacts bearing 0.19% or less of nitrogen and sintered materials under various sintering conditions.
The results were summarized as follows,
(1) Nitrogen in powder compacts was found to decrease the rate constant in vacuum-sintering and to deviate from Arrhenius' plots especially at lower temperature, but was outgassed to 100 ppm or less gradually during vacuum-sintering above 1100°C.
(2) Densification rate was accelerated with denitrogenization, especially for low Ni-15/17% Cr steel powder compacts because of γ-α/γ phase transformation. The singular point on densification curves was shifted to shorter time with an increase of sintering temperature and porosity in green compact.
(3) The residual amount of nitrogen was mainly related to sintering temperature under the influence of pore-closing, and also to specimen-size approximately in the form of rn(T) (r: radius of specimen).
(4) N-addition to original powders had no practical effect on sintered properties, tensile strength and corrosion resistance in 65% HNO3 and 5% H2SO4 solutions when the compacts were vacuum-sintered at 1100°C for 1 hr or more.
