超薄镍基合金P-MPAW焊缝成形特征及微观组织演变

Forming Characteristics and Microstructure Evolution of Ultra-Thin Nickel Base Alloys Welds by P-MPAW

为了获得成形良好的超薄镍基合金焊接接头及其细化的微观组织,课题组基于恒定的平均电流,设计不同脉冲电流参数,采用脉冲微束等离子弧焊(P-MPAW)对100μm厚的镍基高温合金板材进行焊接实验。然后借助超景深显微镜对焊缝的宏观形貌及微观组织进行观察,分析脉冲参数下焊缝成形特征,并采用直线截点法计算焊缝中心的平均晶粒尺寸。结果表明:不同脉冲参数匹配下形成5种焊缝形貌,随着基值电流和脉冲频率的增加,焊缝熔池趋于连续均匀变化趋势。当基值电流为0.8 A、占空比为30%以及脉冲频率为100 Hz时,焊缝中心的平均晶粒尺寸最小。因此,脉冲微束等离子弧焊下,较小的占空比和基值电流以及较大频率的脉冲参数匹配,可获得成形良好且晶粒细化的焊缝。

In order to obtain the well-formed ultra-thin nickel base alloy welded joints and there fine microstructure,different pulse current parameters were designed based on a constant average current.The welding experiment of nickel base superalloy plate with thickness of 100μm was carried out by pulse micro plasma arc welding(P-MPAW).The macroscopic morphology and microstructure of the weld joint were observed with the help of the super depth of field microscope(SDFM),the weld forming characteristics under the pulse parameters were analyzed.The average grain size of the weld joint center was calculated by the straight-line method.The results show that the five kinds of weld joints are formed under different pulse parameters,and the weld pool tends to change continuously and uniformly with the increase of the base current and pulse frequency.When the pulse current parameter is 0.8A,the duty cycle is 30%and the pulse frequency is 100 Hz,the average grain size of the weld center is the smallest.Therefore,a well-formed and finegrained weld joint can be obtained with a smaller duty cycle and base current and a larger frequency of pulse parameters under P-MPAW.