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通过对含W的S32760超级双相不锈钢不同温度时效热处理研究σ相的析出行为.用扫描电镜和透射电镜分析σ相的形貌和化学组成,并研究σ相对力学性能和耐腐蚀性能的影响.在850~1000℃之间,实验钢析出大量由Fe-Cr-Mo-W组成的具有正方结构的σ相,钢板强度和硬度高,塑性差,延伸率低于4%;1050℃时仍存在少量析出,虽然延伸率大幅度提高至31.1%,但冲击韧性离散度高,冲击功偏低;直至1080℃,σ相才能完全溶解至基体中,抗拉强度为640 MPa,延伸率为35.5%,纵、横向冲击功平均值分别达到217 J和110 J.随时效热处理温度升高,点蚀电位提高,点蚀失重率不断下降,1080℃热处理的试样点蚀电位高达1246 m V.该试样在50℃的3.5%Na Cl溶液中腐蚀失重率也仅为0.005~0.007 g·m-2·h-1.
The precipitation behavior of sigma phase was studied by aging heat treatment at different temperatures for S32760 super duplex stainless steel containing W. The morphology and chemical composition of σ phase were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the effect of σ on mechanical properties and corrosion resistance was also investigated. In the range of 850-1000 ℃, a large amount of σ phase with square structure composed of Fe-Cr-Mo-W is precipitated in the experimental steel. The strength and hardness of the steel plate are high, the plasticity is poor and the elongation is lower than 4% Although the elongation rate increased greatly to 31.1%, the impact toughness dispersion was high and the impact energy was low. Until 1080 ℃, the σ phase could completely dissolve into the matrix, the tensile strength was 640 MPa and the elongation was 35.5% , The average value of longitudinal and transverse impact energy is 217J and 110J respectively. With the aging heat treatment temperature increases, the pitting potential increases, the pitting weight loss rate continues to decline, the pitting potential of the sample at 1080 ℃ heat treatment up to 1246 mV. The corrosion loss rate of the sample in 3.5% NaCl solution at 50 ℃ is only 0.005-0.007 g · m-2 · h-1.