Abstract:
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.