Investigations of the microstructure and fracture surface of the pulsed Nd:YAG Laser welding of the 304 Stainless Steel

The present article considers the Nd:YAG pulsed laser welding of 304 stainless steels with two different compositions. The effects of various laser operational parameters and cooling rates on the weld microstructures were considered. The results show that ferritic solidification is produced in the stainless steel with the Creq/Nieq ratio of 1.7, and austenitic solidification is produced in the stainless steel with the Creq/Nieq ratio of 1.61. Moreover, the study shows that by using a high laser power, at high Cooling rate, more ferrite is produced in the stainless steel welds. For the 1.7 Creq/Nieq ratio of stainless steel, the amount of ferrite is increased by using high laser power. In addition, high power laser produced more ferrite in the weld interface of 1.6 Creq/Nieq ratio of stainless steel. Samples were also undergone, proof and burst tests and the fracture surfaces were considered. The fractographic examinations show that the mechanism of the fracture was ductile fracture, and the defects such as porosity, low weld depth may help in producing the fracture of the sample.