Microstructure, Residual Stresses, and Strain-Rate-Dependent Deformation and Fracture Behavior of AISI 304L Joints Brazed with NiCrSiB Filler Metals

Abstract

The knowledge of alloy–process–structure–property relationships is of particular interest for several safety-critical brazed components and requires a detailed characterization. Thus, three different nickel-based brazing filler metals were produced with varying chromium and molybdenum content and were used to braze butt joints of the austenitic stainless steel AISI 304L under vacuum. Two holding times were used to evaluate diffusion-related differences, resulting in six specimen variations. Significant microstructural changes due to the formation and location of borides and silicides were demonstrated. Using X-ray diffraction, alloy-dependent residual stress gradients from the brazing seam to the base material were determined and the thermal-induced residual stresses were shown through simulations. For mechanical characterization, impact tests were carried out to determine the impact toughness, as well as tensile tests at low and high strain rates to evaluate the strain-rate-dependent tensile strength of the brazed joints. Further thermal, electrical, and magnetic measurements enabled an understanding of the deformation mechanisms. The negative influence of brittle phases in the seam center could be quantified and showed the most significant effects under impact loading. Fractographic investigations subsequently enabled an enhanced understanding of the fracture mechanisms.

Microstructure and Defect-Based Fatigue Mechanism Evaluation of Brazed Coaxial Ti/Al2O3 Joints for Enhanced Endoprosthesis Design

“…In addition to the characterization of the brazed seam, investigations on the final cubic ceramic head with the titanium insert are required in the next steps in order to verify, for example, the damping properties of the titanium insert, as already shown by simulation [27]. For this purpose, digital image correlation (DIC) or local strain measurements with strain gauges should be used, as already shown in combination for brazed steel joints in [28]. For further qualification of the brazed joints for use in the human body, biocompatibility tests are essential.…”

Study on Peeling Performance of T-Type Brazing Joints Based on Energy Method

“…Abdolvan [14] designed a new fixture for the shear test of SAF 2507 and AISI 304 dissimilarmaterial brazing joints. Otto JL et al [15] used three different nickel-based brazing filler to brazing joints of AISI 304L under vacuum and then carried out tensile tests at low and high strain rates to evaluate the strain-rate-dependent tensile strength of the brazing joints. It was found that high strain rates increased the ultimate tensile strength of all variations and shifted the other mechanical properties in the high-speed tensile tests.…”