Microstructural evolution during creep of 316LN stainless steel multi-pass weld joints

作者：Vijayanand V D^*; Laha K; Parameswaran P; Ganesan V; Mathew M D

来源：Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 2014, 607: 138-144.

DOI：10.1016/j.msea.2014.03.138

• Electron micrography
• Austenitic stainless steel
• Delta-ferrite morphology
• Multi-pass weld joint
• Intermetallic precipitation
• Creep cavitation

Creep rupture behaviour of 316LN austenitic stainless steel weld joint fabricated by multi-pass shielded metal arc welding process has been studied at 923 K over a stress range of 120-225 MPa. The weld joint exhibited inferior creep rupture strength than the base metal and extensive creep cavitation in weld metal led to the premature failure. Weld metal microstructure was found highly inhomogeneous having different morphologies of delta (delta)-ferrite. The delta-ferrite transformed into intermetallic phases on creep exposure and the creep cavitation was associated with the intermetallic phases. Extensive creep cavitation in weld metal was confined to regions containing delta-ferrite with vermicular morphology. The region near the weld pass interface having globular delta-ferrite was less susceptible to creep cavitation. The globular delta-ferrite region possessed higher hardness than the vermicular delta-ferrite region. High dislocation density was observed in the globular delta-ferrite region which is a consequence of the microstructural modification by the heat input from the successive weld passes. The strength inhomogeneity between the globular and vermicular delta-ferrite regions together with the transformation of delta-ferrite into intermetallic phases produced pronounced creep cavitation in the vermicular delta-ferrite region which led to premature failure of the stainless steel weld joint.

• 出版日期2014-6-23