Investigation of weldability of martensitic stainless steel

In this study, the weldability and mechanical properties of AISI 420J2 martensitic stainless steel were investigated using the fiber laser welding method. The effects of the applied fiber laser welding process on the mechanical properties and microstructure were examined in detail. The microstructure of the welded joints was analyzed using an optical microscope. For the fiber laser welding of AISI 420J2 materials, the optimum welding parameters were determined to be a laser peak power of 1000 W and a welding speed of 3.77 mm/s. Experimental results showed that the materials welded with different parameters fractured at the weld zone in their as-received condition, indicating unsuccessful results. Based on the literature review, it was determined that stress relief annealing should be applied to the materials. After the application of stress relief annealing, tensile tests were conducted on the samples, and it was observed that fracture no longer occurred at the weld zone. Consequently, the microstructure of samples subjected to stress relief annealing after heat treatment was examined. Microstructural analysis revealed that a high amount of delta ferrite led to localized softening, which in turn reduced the hardness of the base metal. Furthermore, it was identified that an excessive presence of delta ferrite in the microstructure could lead to cold cracking.