Brazing of CP-Ti to stainless steel

摘要

Commercially pure titanium (ASTM-Grade 2) and stainless steel (SUS304) were brazed with 2 types of brazing filler metals in this study. One was nickel-based brazing filler metal (TB-902 same as BNi-2) and the other one was 4 kinds of silver-based brazing filler metals (TB-608T, TB-629T, TB-621 and TB-608B). Brazeability of brazed joints was estimated from test results of mechanical properties. Cross-sections of microstructure at the brazed joints were observed by optical microscope and SEM micrographs. Elemental distributions at the brazed joints were analyzed by EDX examinations and crystal structures at fractured surface were analyzed by X-ray diffraction patterns. No joint failures such as voids and cracks were observed at the brazed joints. As a result of shear strength test, all specimens were fractured at reaction layer between stainless steel and brazed layer. Intermetallic compound of sigma-FeCr was formed at the brazed joint with BNi-2. This brittle layer caused to decrease the joint strength. Complicated microstructures were observed at brazed layer on the stainless steel side at the brazed joint with Ag-based filler metals. All fractures were occurred at reaction layer between stainless steel and brazed layer, but Intermetallic compound of sigma-FeCr was not found. Austenitic alloy layer of Fe and Cr was formed at the interface.