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利用光学显微镜、纳米力学探针、扫描电镜、能谱仪和透射电镜等方法,研究了S32760超级双相不锈钢热轧板材经1100℃固溶60 min,并在760~1040℃保温30 min过程中σ相的析出规律,分析了W元素对σ相析出行为的影响。结果表明,σ相中富集大量Cr、Mo和W元素,贫Ni且不含N。W提高了σ相在高温区间的稳定性,使σ相在760~1020℃的范围内均能析出。在析出鼻尖温度880℃时效30 min后,钢板硬度达最大值37.1 HRC,α相体积分数降至5.3%。随着时效温度的升高,σ相的形貌变化规律为:粒状→粒状+短棒状→片层状→块状。在鼻尖温度(880℃)附近,σ相和γ2相以片层共析形貌析出,而在高温阶段(如960℃)则呈现出γ2相被大块σ相包围的形貌。
The microstructures of S32760 super duplex stainless steel were studied by means of optical microscope, nanomechanical probe, scanning electron microscope, energy dispersive spectroscopy and transmission electron microscopy. The results showed that the hot-rolled sheet of S32760 super duplex stainless steel was solvated at 1100 ℃ for 60 min and incubated at 760 ~ 1040 ℃ for 30 min σ phase precipitation law, analysis of the W element on the precipitation of σ-phase behavior. The results show that a large amount of Cr, Mo and W elements are enriched in σ phase, Ni is depleted and N is not contained. W improves the stability of sigma phase in the high temperature range, and makes the σ phase can be precipitated in the range of 760 ~ 1020 ℃. After the tip temperature of 880 ℃ was precipitated for 30 min, the hardness reached 37.1 HRC and the volume fraction of α phase decreased to 5.3%. With the aging temperature, σ phase morphological changes as follows: granular → granular + short rod → lamellar → massive. In the vicinity of the tip temperature (880 ℃), σ phase and γ2 phase are precipitated by lamellar eutectoid morphology, while in the high temperature phase (eg, 960 ℃), the γ2 phase is surrounded by the bulk σ phase.