抄録
In order to clarify the effect of coaxing in 18 Cr-8 Ni austenitic stainless steel at room temperature, progressive stressing fatigue tests were carried out and the fatigue-hardened layers produced by coaxing or non-coaxing were examined by means of microscopy, microhardness test and X-ray diffraction technique.
The results obtained are summarized as follows:
(1) At room temperature the effect of coaxing is observed remarkably in 18-8 stainless steel, and under the progressive stressing conditions of stress increment of 0.85kg/mm2 and cycle increment of 1×105, 1×106 and 1×107 the rate of increase in fatigue strength are 10.8, 14.2 and 20.5per cent, respectively.
(2) The strain-induced martensite transformation takes place during the fatigue deformation process at room temperature and the amount of martensite in the fatigue-hardened layer of specimen under coaxing is much larger than that of non-coaxing specimen.
(3) The strengthening of 18-8 stainless steel caused by the effect of coaxing at room temperature is attributed to the strain-induced martensite transformation as well as the strain aging of the martensite and austenite during fatigue process, and the strengthening due to the former occurs mostly before the fatigue crack initiates.
