Effect of laser and laser hybrid welding on the corrosion performance of a lean duplex stainless steel J. Laser Appl. 22, 150 (2010); 10.2351/1.3533146Microstructural aspects of laser dissimilar welds of hard metals to steels Autogenous Nd:YAG laser welding was carried out on austenitic stainless steel ͑316LN͒ and duplex stainless steel ͑2205͒. The structures were examined using optical and color etching metallography. This showed optically that the austenitic steel solidified as a totally austenitic structure, but the transmission electron microscopy ͑TEM͒ work confirmed the presence of ferrite. In the case of the duplex stainless steel, the solidification structure was almost 100% ferrite. However, the weld metal properties required were met. Dissimilar autogenous Nd:YAG laser welding was performed on a duplex stainless steel to carbon steel joint and on an austenitic stainless steel to carbon steel joint. This revealed the presence of preferential fluid flow to the stainless steel side in the weld metal, and areas of excessive hardness. The results of this study were that filler wire would be required to counteract the high hardness effects induced by the autogenous laser welding process, without having to resort to postweld heat treatment. An evaluation has also taken place of autogenous CO 2 laser welds of D and DH 36 steel. Mechanical properties of the DH 36 steel have been found to be acceptable, and the structure of the D grade material has been examined using TEM, where pearlite and bainite have been identified as being present.

A series of laser and laser assisted metal inert gas (MIG) welds was produced from a common plate. Each weld was mechanically tested, and the welds showed broadly similar properties, except for the autogenous CO2 laser weld metal, which had poorer toughness. This was related to a harder weld metal microstructure. Toughness and hardness were related to the lath width of the ferrite, for the welds involved. The weld metal area/volume was used as an indicator of potential distortion. In this instance, the autogenous CO2 laser weld was superior to the CO2 laser assisted MIG weld which was better than the Nd:YAG laser assisted MIG weld. Each weld was examined using carbon extraction replicas in the TEM, and also using an SEM with an EDAX attachment. A number of inclusions and precipitates were observed, identified and sized. It was concluded that the particles observed were not detrimental in this specific case. A tentative relationship was established between parent plate inclusion size distribution and weld metal inclusion size distribution

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