オーステナイト系304ステンレス鋼の窒素誘起変態
1986 年 50 巻 4 号 p. 362-368
詳細
1986 年 50 巻 4 号 p. 362-368
The nitriding of SUS304 steel was done by d.c. glow discharge plasma in a mixed gas (20 vol%N2+80 vol%H2) under a reduced pressure of 665 Pa at a relatively low temperature of about 623 K. In this nitriding process, the surface layer of the specimen was modified with some surface reliefs such as ion-etched grain boundaries, twins and slip-like straight traces. This layer had a depth of 15-20 μm at the nitriding time of 36.3 ks and the vickers hardness of about 1500 Hv. In this layer, an f.c.t. nitride phase was identified by X-ray diffraction studies.
Subsequent annealing at 723, 823 and 923 K in a vacuum furnace gave rise to the formation of α′ martensite accompanied with the disappearance of the newly developed f.c.t. nitride, but ε martensite was not observed because of its unstability above 573 K.
These processes of phase transformation induced by nitrogen in SUS304 steel strikingly resemble those of hydrogen induced phase transformation in which the f.c.c. hydride is formed by cathodic charging of hydrogen and α′ martensite is formed in its outgassing process by aging.
