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用慢应变速率试验方法在143℃沸腾MgCl_2溶液中研究了不同碳含量、钛的加入量及热处理对Cr18Mo2铁素体不锈钢SCC敏感性的影响。随着碳含量的降低,钢的晶间腐蚀和点腐蚀程度减小,SCC敏感性相应减小。加入适量的钛可以明显减小其SCC敏感性,当Ti/(C+N)比在9.1～13.0时最显著。加入过量的钛引起σ相在晶界附近沉淀,致使SCC敏感性明显增大。经1100℃处理的Cr18Mo2钢,晶间腐蚀程度显著增大,成为SCC敏感性的控制因素,断口呈沿晶开裂,SCC敏感性明显增大。经850℃处理后,晶间腐蚀明显减轻,点腐蚀成为SCC敏感性的主要的影响因素,断口呈穿晶开裂,SCC敏感性显著减小。 Cr18Mo2钢开裂敏感的应变速率为9×10~(*7)s~(-1)。断裂时间、断裂时延伸率ε_f和断面收缩车RA等参数可适用于评价铁素体不锈钢的SCC敏感性。
The effects of different carbon content, titanium content and heat treatment on the sensitivity of Cr18Mo2 ferritic stainless steel to SCC were studied in a slow-strain rate test at 143 ℃ in boiling MgCl 2 solution. As the carbon content decreases, the degree of intergranular corrosion and pitting corrosion decreases, and the SCC sensitivity decreases accordingly. The addition of the appropriate amount of titanium significantly reduced its SCC sensitivity, most notably when the Ti / (C + N) ratio was between 9.1 and 13.0. The addition of excess titanium causes the sigma phase to precipitate near the grain boundaries, resulting in a marked increase in SCC susceptibility. The Cr18Mo2 steel treated at 1100 ℃ increased intergranular corrosion and became the control factor of SCC susceptibility. The fracture of the Cr18Mo2 cracked along the crystal and the SCC sensitivity increased obviously. After 850 ℃ treatment, intergranular corrosion significantly reduced, and pitting corrosion became the main influencing factor of SCC sensitivity. Fracture was transgranular cracking and SCC sensitivity was significantly reduced. Cr18Mo2 steel cracking sensitive strain rate of 9 × 10 ~ (* 7) s ~ (-1). Parameters such as fracture time, elongation at break ε_f, and cross-section reduction RA are suitable for evaluating SCC susceptibility of ferritic stainless steels.