Keyhole plasma arc welding (K-PAW) was used to weld C300 maraging steel in solid-solution state, the microstructure observing and hardness analysis were carried out by optical microscopy transmission electron microscopy, scanning electron microscopy and hardness testing. The results indicate that, in order to avoid local concave it should be appropriate to consider using filler metal during welding C300 maraging steel by means of K-PAW, although good welded joint could be obtained without it. The welded joint with high symmetry could be divided into weld seam zone, solid-solution zone (including coarse grain zone and fine grain region), aging zone and base metal zone. Weld metal showed inverted horn morphology. The hardness peak of the joint was in the aging area, the width of the horizontal area of hardness curve was dependent on the width of the weld seam zone and solid-solution zone.The hardnesses of weld seam zone, solid-solution zone and base metal were the same. Crack morphology and huge difference composition contents of Ni, Mo, Ti and Co were found in aging zone.

采用穿孔型等離子弧(K-PAW)焊接方法對固溶態C300馬氏體時效鋼進行焊接, 并采用光學顯微鏡、透射電子顯微鏡、掃描電子顯微鏡以及硬度儀等對焊接接頭進行了組織觀察和硬度分析。結果表明: 采用K-PAW焊接可得到成形良好的焊接接頭, 但為了避免局部凹陷現象, 應適當采用填充金屬; 焊接接頭具有高度對稱性, 可分為焊縫區、固溶區(粗晶區和細晶區)、時效區以及母材區; 焊縫金屬呈倒喇叭狀形貌; 接頭的硬度峰值出現在時效區, 硬度曲線上水平區域的寬度取決于焊縫區與固溶區的寬度; 焊縫、固溶區與母材的硬度基本相同; 在時效區發現皸裂形貌和鎳、鉬、鈦和鈷元素含量的差異。