Microstructure and Mechanical properties of Dissimilar Welds of Duplex and API Steel for Offshore Applications | ||
| International Journal of Materials Technology and Innovation | ||
| Article 9, Volume 3, Issue 2, June 2023, Pages 80-91 PDF (867.91 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ijmti.2023.207906.1084 | ||
| Authors | ||
| Lawrence OSOBA* 1; Darlington Ekeh2; Taiwo Lawal2; Akeem Mohammed Amuda2 | ||
| 1Department Of Metallurgical & Materials Engineering | ||
| 2Department Of Metallurgical & Materials Engineering, University of Lagos | ||
| Abstract | ||
| Typical offshore area facilities impose stringent structural integrity and safety conditions, often necessitating dissimilar welding (DMW) for joining structural fabrication. Although various combinations of material options have been explored in service and literature, none have been able to prevent or fully justify the failure mechanism observed in the process area. In this study, DMW joints produced from duplex stainless steel (DSS) and API 5L X60 material combination using gas tungsten arc (GTA) welding process were investigated for microstructure and mechanical property evaluation using low (0.73 – 0.88kJ/mm), medium (1.3 – 1.7kJ/mm), and high (2.1 – 2.8kJ/mm) heat inputs. Microstructural characterization of the welded samples suggests the presence of a type II boundary close to and parallel to the fusion boundary close to API 5L X60 base metal. Noticeable presence of macro-segregation at the interfaces between HAZ of the base materials and the weld metal, while high heat input weldment favored the formation of delta ferrite. Morphology of the grains in the HAZ transits from coarse to equiaxed showing typical post-solidification structure with varying grain morphologies. Microhardness evaluation of the HAZ region of both DSS and X60 DMW, indicated a comparable value in all conditions with the low (262/218 HV), high (257/206 HV) and medium (235/220HV) heat inputs, respectively. In the FZ, the medium (192HV) value is intermediate between high (180HV) and low (198HV) heat inputs. The tensile and yield strength of the weldments indicated that the medium heat input has an intermediate value of 439 and 585 HV, respectively. | ||
| Keywords | ||
| dissimilar welds; micro-segregation; heat input; duplex stainless steels; API steels | ||
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