热丝TIG堆焊Inconel 625层组织成形研究

Study on Microstructure Formation of Inconel 625 Surfacing Layer by Hot-wire TIG Welding Process

采用热丝钨极惰性气体保护焊,用ENiCrMo-3型焊丝在Q235B钢管内表面进行堆焊试验。利用金相显微镜、扫描电镜、X射线衍射仪对堆焊层微观组织进行观察和元素成分分析,利用显微硬度计测定试样硬度分布。结果表明,堆焊层组织主要为γ-Ni单相奥氏体,在晶界处有碳化物析出;堆焊层组织自熔合线至顶部的基本形态依次为平面晶、胞晶、树枝晶、等轴晶及顶部横向柱状晶;熔合线附近有少量魏氏体组织形成;试样硬度自基材至堆焊层方向呈递增趋势;上层组织在晶界位置贫Cr较下层严重,从金相看其晶粒受到的侵蚀作用更明显。

The test of overlaying was carried out by welding the inner surface of Q235 Bsteel pipe using the solder wire ENiCrMo-3through hot-wire TIG welding.The microstructure and elemental composition of overlaying layer were investigated by metallographic microscope,scanning electron microscopy,X-ray diffractometer.The hardness distribution of specimen was measured by microhardness tester.The experimental results indicated that the main surfacing layer containedγ-Ni single-phase austenite and carbide precipitates in grain boundary.Moreover,the basic microstructure forms of surfacing layer were plane crystal,cellular grain,dendrite grain,equiaxed grain and the top transverse columnar grain from the fusion line to the top.A small amount of widmanstatten structure was generated near the fusion line.The hardness of specimen increased from substrate to surfacing layer.The chromium depletion at grain boundary in the upper was serious than in the lower,and the grain in upper structure was significantly eroded through metallographic observation.