Abstract

316L(N) stainless steel is an austenitic stainless steel variety strengthened by nitrogen through solid solution hardening. The effects of nitrogen on the mechanical properties of 316L(N) SS have not been studied extensively in the past and is the study of current research. The nitrogen content when added to 316L stainless steel in the range 0.07 wt% - 0.21 wt% improves room temperature and high temperature mechanical properties. The loss in strength due to reduced carbon content in 316L(N) SS can be more or less compensated by the addition of nitrogen. Laser welded joints have been fabricated on 316(L)N SS using CO₂ laser protecting the environment by employing nitrogen shielding and tested the welded joints under tension at room temperature and at 650 ?C (923 K). In the as - welded condition Transmission Electron Microscope (TEM) revealed the presence of the deformation bands, high density of dislocations and carbides or carbo -nitrides on dislocations near the grain boundary regions which may be in the Heat-Affected Zone(HAZ). At both the test temperatures failure occurred in the base metal by transgranuler mode with the nucleation of cavities. In the present work, laser welding process has proved to be effective in producing satisfactory welded joints.

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