Hybrid laser-arc welding of 10-mm-thick cast martensitic stainless steel CA6NM: as-welded microstructure and mechanical properties

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1007/s11661-016-3523-6
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Name affiliation
  1. National Research Council of Canada. Automotive and Surface Transportation
  2. National Research Council of Canada. Aerospace
FormatText, Article
Journal titleMetallurgical and Materials Transactions A
ISSN1073-5623
1543-1940
Volume47
Issue7
Pages3545–3563
SubjectMetallic materials; Nanotechnology; Thin films; Structural materials; Surfaces and interfaces; Characterization of materials; Evaluation of materials
Abstract
Cast CA6NM martensitic stainless steel plates, 10 mm in thickness, were welded using hybrid laser-arc welding. The effect of different welding speeds on the as-welded joint integrity was characterized in terms of the weld bead geometry, defects, microstructure, hardness, ultimate tensile strength, and impact energy. Significant defects such as porosity, root humping, underfill, and excessive penetration were observed at a low welding speed (0.5 m/min). However, the underfill depth and excessive penetration in the joints manufactured at welding speeds above 0.75 m/min met the specifications of ISO 12932. Characterization of the as-welded microstructure revealed untempered martensite and residual delta ferrite dispersed at prior-austenite grain boundaries in the fusion zone. In addition, four different heat-affected zones in the weldments were differentiated through hardness mapping and inference from the Fe-Cr-Ni ternary phase diagram. The tensile fracture occurred in the base metal for all the samples and fractographic analysis showed that the crack path is within the martensite matrix, along primary delta ferrite–martensite interfaces and within the primary delta ferrite. Additionally, Charpy impact testing demonstrated slightly higher fracture energy values and deeper dimples on the fracture surface of the welds manufactured at higher welding speeds due to grain refinement and/or lower porosity.
Publication date
PublisherSpringer International Publishing
PlaceBoston, MA, USA
LanguageEnglish
Peer reviewedYes
Identifier3523
NPARC number23000303
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