Strength of 444 Stainless Steel Single-Lap Joints Brazed with Ni-Based Metallic Glass Foils for Corrosive Environments

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2022-04, Vol.53 (4), p.1407-1418
• Main Authors: Kemmenoe, David J., Theisen, Eric A., Baker, Shefford P.
• Format: Article
• Language: English
• Subjects: Amorphous materials; Base metal; Brazed joints; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion resistance; Failure modes; Foils; Grain boundaries; Grain growth; Lap joints; Materials Science; Metallic glasses; Metallic Materials; Microstructure; Nanotechnology; Original Research Article; Stainless steel; Stainless steels; Strain hardening; Stress state; Structural Materials; Surfaces and Interfaces; Thickness; Thin Films; Ultimate tensile strength; Yield stress
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-022-06601-9

The tensile strengths, σ SLJ , of 444 stainless steel single-lap joints (SLJs) brazed with two corrosion-resistant Ni-based braze filler metals (BFMs) were investigated and compared with results from joints made from 316L stainless steel using identical BFMs and processes. In previous work, we proposed that σ SLJ could be understood in terms of SLJ geometry (primarily the ratio of overlap length o to plate thickness t —which determines the stress state), base metal properties (which determine stress state evolution with load), and braze microstructure (which determines local failure stress). The geometry and braze microstructure were varied in the prior work. The present study shows the effect of the base metal. 444 has higher yield stress, lower ultimate strength, and less strain hardening than 316L, and also experiences significant grain growth above 1100 °C. Although the braze microstructures of SLJs made using 444 are very similar to those of their 316L counterparts, not only σ SLJ , but also variations of both σ SLJ and failure mode with o / t are very different. Differences are not simply due to ultimate strength as is commonly assumed, but to how plasticity controls joint rotation and thus stress state during loading, as well as through-thickness grain boundaries acting as failure sites.