The Study of Infrared brazing Ti50Ni50 SMA and 316L Stainless Steel/Inconel 600
Date Issued
2015
Date
2015
Author(s)
Yang, Sheng-Hao
Abstract
BAg-8, Cusil-ABA, Ticusil, and Copper fillers are used to infrared braze Ti50Ni50 and two other alloys, 316L stainless steel(SS) and Inconel (IN) 600. The brazed joint’s interfacial reaction, microstructure evolution and shear strength are investigated. Cu film is used as a diffusion barrier in the filler with three layers (BAg-8/Cu/Cusil-ABA) to prevent the formation of brittle Fe-Ti intermetallics in TiNi/316L joint. For TiNi/ BAg-8/Cu/Cusil-ABA /316L joint, it is composed of (CuxNi1-x)2Ti, Cu-rich, Cu, and Ag-Cu eutectic. When the thickness of cu film is 70μm, the shear strength is 292MPa for the joint brazed at 820℃×5min. If the Cu film thickness reduces to 50μm, the joint’s shear strength can reach 349 MPa when it is brazed at 850℃×5min. However, when thickness is reduced to 25μm, it can not prevent the formation of brittle Fe-Ti intermetallics and the shear strength reduces to 236 MPa. For IN600, the wettability of BAg-8 is degraded by surface CrxOy oxides, but the Ti in Cusil-ABA/Ticusil can improve the wettability significantly. TiNi/Bag-8/IN600 joint is composed of Ni3Ti, Ag-Cu eutectic and Cu-rich, and has the average shear strength of 72MPa when it is brazed at 850℃×5min. This joint is fractured along Ni3Ti. For Cusil-ABA and Ticusil brazed joints, the sequence of identified phases from TiNi to IN600 is CuNiTi, Ag-Cu eutectic and the mixture of CuNiTi and Ni3Ti. The specimen brazed at 900℃×5min using Cusil-ABA filler demonstrates the best shear strength of 324 MPa. The shear strength of TiNi/Ticusil/IN600 joint brazed at 950℃×3min is 300 MPa. When the brazing time increases, the shear strength of the jonit used Ticusil filler decreases due to the growth of Ni3Ti intermetallics in which cracks are initiated from Ni3Ti and the fractograph is dominated by quasi-cleavage fracture.
Subjects
Infrared brazing
316LSS
Ag-based fillers
diffusion barrier
Type
thesis
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