Inconel 718合金钨极惰性气体保护焊的热循环

摘要

采用热动源模型和瞬态热分析相结合,并借助于有限元方法,确定在Inconel 718合金板上应用钨极惰性气体保护焊获得的焊接热循环和等温截面.Rosenthal厚板模型和有限元分析结果显示,焊接热循环与实验值较相近.与实验曲线相比,用双椭圆模型热分布数值模拟确定的等温截面其拟合效果优于高斯模型.为了分析不同冷却速率下熔融区和热影响区显微组织的转变,进行维氏显微硬度测量(由横截面硬度分布曲线和纵截面硬度分布映射图表示).与基体材料的显微硬度(～350 HV0.2)相比,热影响区(～200 HV0.2)和熔融区(～240 HV0.2)的显微硬度降低,这是由于根据连续冷却转变曲线,γ″相(镍基体)的不均匀溶解过程生成Laves相、δ相和金属间化合物过渡相,使熔融区的硬度值降低.%Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal's thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (～200 HV0.2) and fusion zone (～240 HV0.2) in comparison with base material (～350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling?transformation curve, produced the Laves phase, δ and MC transition phases, generating a loss in hardness close to the fusion zone.