Transient liquid phase bonding of AISI 304L stainless steels with the austenitic and martensitic microstructures

In the present study, the effect of time and base metal microstructure on the Transient Liquid Phase (TLP) bonding of 304L stainless steel was studied. TLP was performed at 1050 0C for 5 and 60 minutes on the coarse grain austenitic and martensitic microstructure using BNi-2 interlayer. To prepare martensitic microstructure, as-received 304L was rolled at -15 0C up to 80% rolling reduction. TEM analysis was proved that the microstructure of 80% rolled samples consisted of two different morphologies of martensite namely as lath-type and dislocation cell type martensite.  It was observed that the structure of bonded zone after 5 min has consisted of isothermally solidified zone (ISZ) containing γ solid solution and athermally solidified zone (ASZ) containing complex boride phases. Meanwhile, after 60 min of  heating, the structure of bonded zone completely solidifies isothermally. The obtained results also showed that the martensitic microstructure considerably effect on the width of diffusion affected zone (DAZ) which was related to the reversion of martensite to ultrafine grain austenite during heating.