Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel and nickel base alloys
Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel and nickel base alloys
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DOI：
10.1179/136217102225006804
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发表时间：
2002-12-01
影响因子：
3.3
通讯作者：
Marder, AR
中科院分区：
文献类型：
--
作者：
Banovic, SW;DuPont, JN;Marder, AR
超级奥氏体不锈钢通常使用高Mo、Ni基填充金属进行焊接，以保持焊缝的耐腐蚀性。该处理的一个重要方面是焊缝金属稀释水平，其将控制焊缝的成分和由此产生的耐腐蚀性。此外，焊缝中合金元素的分布也将显著影响耐腐蚀性，超级奥氏体不锈钢（AL-6XN）和两种镍基合金（IN 625和IN 622）之间的异种金属焊缝的特征在于其稀释水平和显微偏析模式。在整个稀释范围内使用钨极气体保护焊工艺产生单道焊缝。采用光学显微镜、扫描电子显微镜和定量图像分析对焊缝进行显微组织表征。通过电子探针微区分析获得了整体和局部的化学成分。定量化学信息被用来确定在每个异种焊缝中的元素的分配系数k。发现稀释水平随着体积填充金属进给速率与净电弧功率的比率的增加而降低。这种行为的原因进行了讨论，在所需的功率分配熔化的填充金属和基体金属。此外，随着焊缝中Fe含量的增加，观察到Mo和Nb的偏析可能性增加（即它们的k值降低）。这是由于随着Fe添加量的增加，Mo和Nb在奥氏体中的溶解度降低。由于焊缝的Fe含量由稀释控制，而稀释又由焊接参数控制，因此焊接参数对Mo和Nb的偏析可能性具有间接影响。本工作的结果提供了实际的洞察力超级奥氏体不锈钢焊缝的腐蚀控制。
Super austenitic stainless steels are often welded using high Mo, Ni base filler metals to maintain the corrosion resistance of the weld. An important aspect of this processing is the weld metal dilution level, which will control the composition and resultant corrosion resistance of the weld. In addition, the distribution of alloying elements within the weld will also significantly affect the corrosion resistance, Dissimilar metal welds between a super austenitic stainless steel (AL-6XN) and two Ni base alloys (IN625 and IN622) were characterised with respect to their dilution levels and microsegregation patterns. Single pass welds were produced over the entire dilution range using the gas tungsten arc welding process. Microstructural characterisation of the welds was conducted using light optical microscopy, scanning electron microscopy, and quantitative image analysis. Bulk and local chemical compositions were obtained through electron probe microanalysis. The quantitative chemical information was used to determine the partition coefficients k of the elements in each dissimilar weld. The dilution level was found to decrease as the ratio of volumetric filler metal feedrate to net are power increased. Reasons for this behaviour are discussed in terms of the distribution of power required to melt the filler metal and base metal. In addition, the segregation potential of Mo and Nb was observed to increase (i.e. their k values decreased) as the Fe content of the weld increased. This effect is attributed to the decreased solubility of Mo and Nb in austenite with increasing Fe additions. Since the Fe content of the weld is controlled by dilution, which in turn is controlled by the welding parameters, the welding parameters have an indirect influence on the segregation potential of Mo and Nb. The results of the present work provide practical insight for corrosion control of welds in super austenitic stainless steels.