高Mo超级奥氏体不锈钢耐Cl-腐蚀性能分析
Analysis of Cl- Corrosion Resistance of High Mo Super Austenitic Stainless Steels
通讯作者: 吕迎玺,E-mail:LYX6746@163.com,研究方向为金属材料
收稿日期: 2022-04-09 修回日期: 2022-05-10
Corresponding authors: LV Yingxi, E-mail:LYX6746@163.com
Received: 2022-04-09 Revised: 2022-05-10
作者简介 About authors
吕迎玺,男,1965年生,高级工程师
对比分析了不同Mo含量的316L、904L、S31254和S31254-B奥氏体不锈钢在10%NaCl溶液中的腐蚀行为,及其固溶处理、低温时效处理对其耐蚀性的影响;利用扫描电子显微镜、电化学极化曲线和电化学阻抗谱对4种不锈钢的显微组织、耐蚀性和表面腐蚀形貌进行了分析。结果表明:4种不锈钢在10%NaCl溶液中有不同的耐蚀性能,耐蚀性排序为:低温时效态>固溶态,S31254-B>S31254>904L>316L。Mo含量的提高、微量合金元素B加入奥氏体、低温时效处理均有利于提升材料的耐蚀性能。B促使表面形成富Cr、Mo氧化物的钝化膜,提升钝化层的致密化,减缓晶界处贫Cr、贫Mo区,提高耐蚀性。
关键词:
The increase of Mo content can improve the corrosion resistance of austenitic stainless steel. In this paper, the corrosion behavior of four austenitic stainless steels 316L, 904L, S31254 and S31254-B with different Mo content in 10%NaCl solution has been comparatively examined. The effect of solution treatment and low temperature aging treatment on the corrosion resistance of steels was compared. The microstructure, corrosion resistance and surface corrosion morphology of the four stainless steels were characterized by means of scanning electron microscope, electrochemical scanning polarization curves and electrochemical impedance spectroscope. The results show that the four stainless steels present different corrosion performance in 10%NaCl solution, their corrosion resistance can be ranked as follows: low temperature aging state>solid solution state for all steels; whilst S31254-B>S31254>904L>316L. The increase of Mo content, the addition of B and the aging treatment at low temperature can improve the corrosion resistance of the steels. Meanwhile, B can promote the formation of Cr- and Mo-rich oxides in the outer layer of passivation film, which makes the surface of passivation film much compact, and the lean-Cr and -Mo regions at grain boundaries can be slowed down, therewith the corrosion resistance of the steels can be improved significantly.
Keywords:
本文引用格式
吕迎玺.
LV Yingxi.
超级奥氏体不锈钢中均含有很高Mo,可提高不锈钢的抗点蚀、抗晶间腐蚀能力,但是Mo在热加工过程中又极易形成析出相,降低耐蚀性。已有研究表明,低温时效有利于促进Cr向晶界的聚集,若不形成碳化物有利于耐蚀性的提高,即合理的热处理工艺,超奥钢充分的固溶处理有利于使析出相回溶提高耐蚀性,但是低温时效是否会促使Cr、Mo的晶界再分配,这方面在超奥钢中的研究却很少。硼微合金化也可抑制析出相的析出、提高耐蚀性[10-14],为此本文选取Mo较高的系列奥氏体不锈钢316L、904L、S31254、S31254-B,对其固溶处理后试样进行低温时效处理,分析其耐蚀性能,以便研究Mo、B对材料钝化膜结构和耐蚀性能的影响,为苛刻环境使用的超奥钢提供指导。
1 实验方法
实验材料为太原钢铁集团有限公司生产的材质为316L、904L、S31254、S31254-B高Mo超级奥氏体不锈钢热轧钢板,主要化学成分 (质量分数,%) 见表1所示。
表1 4种不锈钢的化学成分
Table 1
Sample | C | Si | Mn | P | S | Cr | Ni | Mo | Cu | N | B |
---|---|---|---|---|---|---|---|---|---|---|---|
S31254-B | 0.014 | 0.84 | 0.98 | 0.012 | 0.001 | 20.23 | 18.05 | 6.23 | 0.85 | 0.242 | 0.004 |
S31254 | 0.012 | 0.61 | 0.93 | 0.010 | 0.002 | 20.17 | 18.15 | 6.03 | 0.72 | 0.212 | --- |
904L | 0.011 | 0.52 | 1.29 | 0.018 | 0.001 | 20.10 | 24.31 | 4.42 | 1.42 | 0.06 | --- |
316L | 0.015 | 0.54 | 1.74 | 0.042 | 0.002 | 16.30 | 10.31 | 2.45 | --- | --- | --- |
用线切割机截取试样,尺寸为15 mm×15 mm× 3 mm。热处理前在试样外表面涂抹抗氧化液,防止高温氧化,随后将试样置于KSL-1200X箱式炉中,温度调至1220 ℃固溶处理,保温1 h后淬水冷却;部分固溶处理后试样再进行410 ℃低温时效处理,保温3 h后淬水冷却。热处理后的试样背面焊接导线,用亚克力粉和硬化剂对试样进行冷镶嵌,最后在试样周围涂装一圈硅胶密封,干燥备用。
试样依次采用180、240、400、600、800、1000、1500、2000、3000目SiC砂纸磨平,机械抛光至表面呈镜面,抛光后用蒸馏水冲洗,再用无水乙醇洗净吹干。采用王水化学浸蚀剂,显示出显微组织。利用Vega 3 XMV型扫描电子显微镜 (SEM) 观察显微组织。采用UltimMax170能谱分析仪 (EDS) 分析试样时效处理区晶界区的元素分布。
模拟试样在室温常压下Cl-环境中的腐蚀,使用CS350电化学工作站及配套的CorrTest测试软件对实验数据进行采集。实验介质为10% (质量分数) NaCl溶液,以饱和甘汞电极作为参比电极,铂电极作为对电极,平板腐蚀电解池作为腐蚀实验装置,工作面积为1 cm2。实验前先将试样在溶液中浸泡60 min,测定稳态开路电位,待开路电位稳定后,自开路电位-200 mV以0.5 mV/s的速率进行动电位极化曲线测试,以便分析极化曲线的特征值。使用幅值为10 mV的正弦波作为扰动信号,测试频率范围为105~10-2 Hz,从高频向低频扫描,进行电化学阻抗谱测试,Zview软件进行数据分析,以便分析样品表面钝化膜的电化学行为。每组实验做3组平行实验。用无水乙醇以及丙酮擦净试样表面,观察腐蚀形貌。
2 结果与讨论
2.1 显微组织分析
4种不锈钢在1220 ℃固溶处理1 h水淬后所得固溶态的显微组织如图1所示,均是单一奥氏体组织,均存在大量孪晶,未见明显析出相,316L不锈钢晶粒尺寸相对较小,约在100~150 μm,孪晶最多,904L不锈钢晶粒尺寸、S31254和S31254-B不锈钢晶粒尺寸略微大些,约200 μm左右。
图1
图1
4种不锈钢1220 ℃固溶处理后显微组织
Fig.1
Micrographs of the solution-treated sample of 316L (a), 904L (b), S31254 (c), S31254-B (d) stainless steel
4种不锈钢在1220 ℃固溶处理后并于410 ℃低温时效处理3 h水淬后所得的显微组织如图2所示,均是单一奥氏体组织,仍然存在大量孪晶,较固溶态相比仍然晶界非常清晰,没有看到析出相的存在,晶粒尺寸与固溶组织接近,没有发生太多的变化。
图2
图2
4种不锈钢固溶并410 ℃低温时效处理后显微组织
Fig.2
Micrographs of the aging-treated sample of 316L (a), 904L (b), S31254 (c), S31254-B (d) stainless steel
S31254-B不锈钢经410 ℃低温时效处理后晶界区域能谱分析如图3所示,Cr、Mo等元素在晶界并没有聚集现象,即没有析出相的形成。
图3
图3
S31254-B不锈钢经410 ℃低温时效处理后晶界区域能谱分析
Fig.3
EDS of grain boundary region of S31254-B stainless steel after low temperature aging at 410 ℃
2.2 耐蚀性能分析
图4
图4
4种不锈钢在10%NaCl溶液中的极化曲线
Fig.4
Potentiodynamic polarization curves of solution-treated sample of 316L, 904L, S31254, S31254-B stainless steel (a), aging-treated at 410 ℃ sample of 316L, 904L, S31254, S31254-B stainless steel (b), solution-treated and aging-treated at 410 ℃ sample of 316L, 904 stainless steel (c), solution-treated and aging-treated at 410 ℃ sample of 31254-B, S31254 stainless steel (d) in 10%NaCl solution
表2 4种不锈钢极化曲线特征值
Table 2
Heat treatment | Icorr / 107 A·cm-2 | Ecorr / VSCE | Epit / VSCE |
---|---|---|---|
Solution-treated of 316L stainless steel | 1.058 | -0.330 | 0.431 |
Aging-treated at 410 ℃ of 316Lstainless steel | 1.183 | -0.320 | 0.450 |
Solution-treated of 904L stainless steel | 0.833 | -0.304 | 1.014 |
Aging-treated at 410 ℃ of 904L stainless steel | 0.877 | -0.319 | 1.028 |
Solution-treated of S31254 stainless steel | 0.910 | -0.300 | 1.092 |
Aging-treated at 410 ℃ of S31254 stainless steel | 1.024 | -0.298 | 1.096 |
Solution-treated of S31254-B stainless steel | 0.617 | -0.212 | 1.125 |
Aging-treated at 410 ℃ of S31254-B stainless steel | 0.536 | -0.111 | 1.232 |
4种不锈钢的动电位极化曲线具有相同的趋势,均存在明显的钝化区,说明其腐蚀机理基本相同。极化曲线特征值中,自腐蚀电位Ecorr排序:410 ℃低温时效态>固溶态,固溶态S31254-B>S31254>904L>316L,410 ℃低温时效态S31254-B>S31254>904L>316L;点蚀电位Epit排序:410 ℃低温时效态>固溶态,固溶态S31254-B>S31254>904L>316L,410 ℃低温时效态S31254-B>S31254>904L>316L。点蚀电位Epit是电流密度开始随电位增大而快速增大的起始电位,是评价材料点蚀敏感性的重要指标,一般认为点蚀电位越正,材料的耐点蚀性能越好[15]。4种不锈钢的耐点蚀性排序:410 ℃低温时效态>固溶态,S31254-B>S31254>904L>316L。这是由于不锈钢在低温时效处理过程中,由于温度很低,难以形成Cr23C6类型的析出相,但是会使得Cr等在晶界富集,从而提高晶界的抗腐蚀性能[16,17];固溶态基体组织中也没有析出相,同样也具有较好的耐点蚀性能,但是就其晶界来讲,较低温时效处理试样的耐点蚀性能略差。对于316L和904L不锈钢进行对比,Mo含量增加,有利于形成稳定钝化膜,耐蚀性得到提高[15]。对S31254和S31254-B不锈钢进行对比,微量合金元素B的加入可以提高材料的耐点蚀性能,这是由于B可以使得基体组织中的第二相快速溶解并且抑制析出相的生成,从而使得材料获得更稳定且致密的钝化膜[16,17]。
图5
图5
4种不锈钢在10%NaCl溶液中电化学阻抗谱
Fig.5
Impedance spectroscopy of solution-treated sample of 316L, 904L, S31254, S31254-B stainless stain (a), aging-treated at 410 ℃ sample of 316L, 904L, S31254, S31254-B (b), solution-treated and aging-treated at 410 ℃ sample of 31254-B, S31254 (c) and solution-treated and aging-treated at 410 ℃ sample of 316L, 904 stainless steel (d) in 10%NaCl solution
2.3 表面腐蚀形貌分析
4种不锈钢在1220 ℃固溶处理1 h水淬后试样经电化学腐蚀后的腐蚀形貌如图6所示。316L不锈钢腐蚀坑数量较多,尺寸较大,904L不锈钢有极少量腐蚀坑,S31254不锈钢和S31254-B不锈钢未见明显腐蚀坑。
图6
图6
4种不锈钢固溶处理后动电位极化后表面形貌
Fig.6
Surface corrosion morphologies of the solution-treated sample of 316L (a), 904L (b), S31254 (c), S31254-B (d) stainless steel after potentiodynamic polarization
4种不锈钢在1220 ℃固溶处理1 h水淬后并410 ℃低温时效处理3 h水淬后试样经电化学腐蚀后的表面腐蚀形貌如图7所示。316L不锈钢表面点蚀坑数量较多,尺寸较大,其余3种钢未见明显腐蚀坑,但是904L不锈钢有一些非常微小的孔洞,而S31254不锈钢表面非常干净。
图7
图7
4种不锈钢固溶并410 ℃时效后动电位极化后表面形貌
Fig.7
Surface corrosion morphologies of the aging-treated sample of 316L (a), 904L (b), S31254 (c), S31254-B (d) stainless steel after potentiodynamic polarization
2.4 对比分析
4种不锈钢分别经过1220 ℃固溶处理1 h,410 ℃低温时效处理3 h,这两种不同的热处理工艺。410 ℃低温时效态试样的自腐蚀电位、点蚀电位、容抗弧半径均高于固溶态试样,即低温时效态耐蚀性明显高于固溶态。
3 结论
(1) 316L、904L、S31254、S31254-B 4种高钼超级奥氏体不锈钢固溶后显微组织为单一奥氏体组织,且孪晶数量很多,经410 ℃低温时效处理后,有利于改善耐蚀性,晶界仍无析出相的析出。
(2) 316L、904L、S31254、S31254-B 4种高钼超级奥氏体不锈钢耐10%NaCl溶液腐蚀的顺序:316L<904L<S31254<S31254-B。
(3) 在奥氏体不锈钢中,增加Mo含量、加入微量B,均可促使奥氏体不锈钢表面形成富Cr、Mo氧化物,且钝化膜更加致密,耐点蚀性提高。微量合金元素B还可以抑制析出相的生成,从而使得材料具有更稳定、致密的钝化膜,提高了不锈钢材料整体的耐点蚀性能。
参考文献
Experience in effective application of metallic materials for construction of FGD systems
[R].
High specialty stainless steels and nickel alloys for FGD dampers
[R].
RETRACTED: Future sustainable water desalination technologies for the Saudi Arabia: A review
[J].
Selection of engineering material of distillation of seallater with low temperature and multi-effect function
[J].
低温多效海水淡化工程材料的选用
[J].
Analyses and protection of seawater cooling system in offshore oil platform
[J].
某石油平台海水冷却系统腐蚀分析与防护方法
[J].
Pitting corrosion of several super stainless steels in a simulated water environment of low temperature multi effect desalination unit
[J].
几种超级不锈钢在模拟低温多效海水淡化环境中的点蚀行为研究
[J].
Corrosion behavior of several metal materials in blast furnace gas condensates
[J].
几种金属材料在高炉煤气管道冷凝液中的电化学腐蚀行为
[J].
Electrochemical studies of 254SMO stainless steel in comparison with 316L stainless steel and Hastelloy C276 in phosphoric acid media in absence and presence of chloride ions
[J].
Effects of Mo addition and austenitizing temperature on hardenability of low alloy B-added steels
[J].
A grain boundary characterization study of boron segregation and carbide precipitation in alloy 304 austenitic stainless steel
[J].
Comparison of SCC behavior of 304L stainless steels with and without boron addition in acidic chloride environment
[J].
Effects of boron on microstructure and metastable pitting corrosion behavior of Super304H austenitic stainless steel
[J].
Effect of Ni and B on the hot workability of high Mo austenitic stainless steels
[J].
Microstructural evolution and pitting corrosion behavior of friction stir welded joint of high nitrogen stainless steel
[J].
Intergranular corrosion behavior of low-chromium ferritic stainless steel without Cr-carbide precipitation after aging
[J].
Corrosion resistance and passivation behavior of B-containing S31254 stainless steel in a low pH medium
[J].
Corrosion behavior of 904L austenitic stainless steel in hydrofluoric acid
[J].
Influence of pH on the passivation behavior of 254SMO stainless steel in 3.5%NaCl solution
[J].
Electrochemical characterisation of a martensitic stainless steel in a neutral chloride solution
[J].
Characterization of passive film on 2205 duplex stainless steel in sodium thiosulphate solution
[J].
Influence of pH on the passivation behaviour of 904L stainless steel bipolar plates for proton exchange membrane fuel cells
[J].
Corrosion behavior of four corrosion-resistant alloys in ultra-supercritical boiler flue gas condensate
[J].
4种耐蚀合金在超超临界锅炉烟气冷凝液中的腐蚀行为研究
[J].
Pitting Behavior of two stainless steels in simulated heavy water reactor primary solution and 3.5%NaCl solution
[J].
两种不锈钢在模拟重水堆一回路溶液和
Effect of sensitization treatment on electrochemical corrosion and pitting corrosion properties of 00Cr21NiMn5Mo2N stainless steel
[J].
敏化处理对00Cr21NiMn5Mo2N节镍型双相不锈钢堆焊层电化学腐蚀与点蚀性能的影响
[J].
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