氮含量與熱處理後之σ相析出量對2205雙相不銹鋼耐蝕性質之影響

Effects of Nitrogen Content and σ Phase by Aging Treatments on the Corrosion Resistance of 2205 Duplex Stainless Steel

王博正(Po-Eng Wang) ； 劉宏義(Horng-Ih Liou)

《鑛冶：中國鑛冶工程學會會刊》 42卷4期 (1998/12) Pp. 73-82+72

https://doi.org/10.30069/MM.199812_42(4).0010

摘要

本研究變化不同氮含量及時效熱處理，來探討氮含量及σ相析出量對雙相不銹鋼耐蝕性之影響。實驗方法包括金相定量分析，硫酸浸泡試驗、電化學試驗及硫酸鐵／硫酸試驗。結果發現：氮含量增加會提高γ相之相比例，且減少σ相析出量。而σ相析出量會隨時效處理時間之增長而增加，當時效時間長達100小時，三種材料之σ相之體積為達30～40%；另外，α相的含量增加時，可明顯降低雙相不銹鋼在硫酸中之均勻腐蝕速率，表示α相相對於γ相有較優良的耐均勻腐蝕能力；雙相不銹鋼中σ相越多，均勻腐蝕速率越增加，當σ相含量達到10%以上時，會呈現飽和的現象（6000mpy）。其不易受腐蝕的部分為σ相，而周圍之γ_2或γ相均因伽凡尼效應而優先腐蝕；氮含量添加會提高雙相不銹鋼之Enp及Epp值，而σ相含量增加，材料之抗孔蝕能力隨之下降，臨界的σ相含量在5%左右；雙相不銹鋼之σ相析出，也會發生類似敏化現象，而使材料引起沿晶腐蝕，其主要被腐蝕組織為γ_2相，而留下γ相及σ相。

關鍵字

雙相不銹鋼 ； 氮含量 ； 時效熱處理 ； 析出相 ； 耐蝕性質

並列摘要

The effects of nitrogen content and σ phase by aging treatments on the corrosion resistance of 2205 duplex stainless steel (DSS) have been investigated in this study. The experimental methods included image analysis, immersion corrosion test, electrochemical test and intergranular corrosion test. The results showed that increase of nitrogen content would promote the formation of γ phase and inhibit the precipitation of σ phase. The amount of α phase would grow to 30~40 %, when the time of aging treatment was prolonged. When the volume of σ phase increased, the general corrosion rate of DSS in sulfuric acid solution would be reduced. However, increasing σ phase deteriorated the corrosion resistance of DSS. The corrosion rate would present a saturation phenomenon (6000 mpy) when the volume of σ phase exceeded 10 %. The preferential corrosion regions were rather γ_2 and γ phases than σ phase according to galvanic effect. The addition of nitrogen would also increase Enp and Epp of DSS, but the pitting resistance would drop as the σ phase increased. The critical volume of σ phase was about 5 %. DSS, like traditional stainless steel, would also occur sensitization owing to a phase precipitation after long aging treatment. Therefore, γ_2 phase was the major microstructure to be corroded resulting in the retainment of γ and σ phases.

並列關鍵字

Duplex stainless steel ； Nitrogen content ； Aging reatment ； σ phase ； Corrosion resistance