基于团簇式的316不锈钢成分优化及其实验验证
首发时间:2024-04-30
摘要:316不锈钢因其优异的耐蚀和加工性能而得到广泛应用,但其宽泛的成分范围会导致性能波动。本文首先将置换型固溶合金化元素归类为稳定铁素体的类Cr元素(Cr,Si,Mo)和稳定奥氏体的类Ni元素(Ni,Mn)。进而引入"团簇加连接原子"模型,给出该不锈钢的16原子成分单元,由此将现有国标成分区间解析成五个16原子成分式,分别对应于两类元素的上下限(Cr,Si,Mo)3.0625,3.5-(Ni,Mn)1.75,2.25-Febal和中值(Cr,Si,Mo)3.25-(Ni,Mn)2-Febal。采用氩气保护电弧炉熔炼,用真空箱式炉实施均匀化处理(1150 ℃/2h,炉冷),冷轧至5mm薄片(变形量约50%),再实施固溶处理(1050 ℃/0.5h,水淬)。进而进行铸态和时效态样品的结构表征和性能测试。含有最低类Ni元素的Cr3.5-Ni1.75-Febal和Cr3.0625-Ni1.75-Febal合金组织中出现铁素体相,对应的质量百分比成分区间为(21.2~18.5)(Cr, Si, Mo)-11.4(Ni, Mn)-Fe;其它三个样品均为单一奥氏体相。经固溶后,平均维氏硬度约为160,最高为174,均满足国标要求(低于200)。在3.5 wt.% NaCl溶液中的电化学腐蚀实验结果表明,类Cr元素含量最高的Cr3.5-Ni2.25-Febal合金(Fe-17.8Cr-0.6Si-2.7Mo-14.0Ni-0.8Mn-0.021C)体现出最强的耐蚀性能,成分式中类Ni元素原子个数在2以上的Cr3.0625-Ni2.25-Febal和Cr3.25-Ni2-Febal也表现出较强的耐蚀性,对应的质量百分比成分区间为(18.4~21.1)(Cr, Si, Mo)-(14.7~13.0)(Ni, Mn)-Fe。根据耐点蚀当量和极化曲线的结果可知,类Cr元素含量高的316不锈钢耐点蚀当量高(26.7),点蚀电位(0.211V)也高,表现出更优异的耐点蚀性能。综合考虑,成分式区间的中值合金Cr3.25-Ni2-Febal(Fe-16.7Cr-0.4Si-2.7Mo-11.9Ni-1.2Mn-0.021C)既能形成单相奥氏体,又具有满足标准要求的维氏硬度(~ 160 HV),并且其耐蚀性也在高的水平(自腐蚀电位-0.082 V、腐蚀电流密度1.83*10-6 A cm-2、点蚀当量25.6、点蚀电位0.19 V),合金化元素含量适中,是最佳合金。
关键词: 316不锈钢 团簇加连接原子模型 团簇式 显微组织 点蚀
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Cluster-formula-based composition optimization of 316 stainless steel and experimental validation
Abstract:316 stainless steel is widely utilized due to its exceptional corrosion resistance and processibility. However, the broad composition range specified by the industrial standards can lead to important property variations. In this study, we first classify the solute elements of substitutional type into Cr-like ferrite stabilizers (Cr,Si,Mo) and Ni-like austenite stabilizers (Ni,Mn). Then we employ the "cluster-plus-glue-atom" model to obtain its composition unit, which contains 16 atoms. Accordingly, the GB standard is interpreted as being enclosed by five 16-atom formulas, corresponding respectively to the lower and upper limits of Cr- and Ni-like elements (Cr,Si,Mo)3.0625,3.5-(Ni,Mn)1.75,2.25-Febal and the mid-value (Cr,Si,Mo)3.25-(Ni,Mn)2-Febal. The alloys are melted by Ar-atmosphere arc furnace. In vacuum heat furnaces, they are homogenized (1150 ℃/2h/furnace cooling), cold-rolled (50% deformation) to 5mm sheets, and finally solutioned (1050 ℃/0.5h/water quenching). The as-cast and solutioned samples are characterized for microstructures and properties. Alloys Cr3.5-Ni1.75-Febal and Cr3.0625-Ni1.75-Febal, containing the lowest Ni-like content of 1.75 in the 16-atom formulas (10.9 at.%), form ferrite in austenite matrix, corresponding to wt.% range of (21.2~18.5)(Cr, Si, Mo)-11.4(Ni, Mn)-Fe. The other three samples contain only pure single austenite phase. The average hardness value after rolling and solutioning is approximately 160 HV, satisfying the GB requirement (< 200 HV). The electrochemical tests in 3 wt.%NaCl solution demonstrates that the alloy Cr3.5-Ni2.25-Febal (Fe-17.8Cr-0.6Si-2.7Mo-14.0Ni-0.8Mn-0.021C), with the highest Cr-like element content, possesses the best corrosion resistance, next to it are alloys Cr3.0625-Ni2.25-Febal and Cr3.25-Ni2-Febal, containing Ni-like element above 2 in the formulas, covering a wt.% composition range of (18.4~21.1)(Cr, Si, Mo)-(14.7~13.0)(Ni, Mn)-Fe. After Pitting Resistance Equivalent Number (PREN) and the electrochemical corrosion tests, the alloys containing the highest Cr-like contents of 3.5 show the best pitting corrosion resistance with PREN = 26.7 and pitting corrosion potential 0.211 V. Generally speaking, the alloy Cr3.25-Ni2-Febal(Fe-16.7Cr-0.4Si-2.7Mo-11.9Ni-1.2Mn-0.021C), falling in the middle of the formula zone, is the best fir its forming pure austenite, a satisfactory low hardness (~160 HV), fairly high corrosion resistances (self-corrosion potential -0.082 V, corrosion current density 1.83*10-6 A cm-2, PREN 25.6, and pitting corrosion potential 0.19 V), and proper amounts of alloying elements.
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基于团簇式的316不锈钢成分优化及其实验验证
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