The effect of bonding time on the microstructure and mechanical properties of transient liquid phase bonding between SAF 2507 and AISI 304
The aim of this study was to evaluate the effect of the bonding time on the transient liquid phase (TLP) bonding of SAF 2507 super duplex stainless steel to AISI 304 austenitic stainless steel. The bonding process was carried out at 1050 °C for different bonding times of 5, 10, 30 and 45 min to achieve a joint free of the inter-metallic compounds. For this purpose, an amorphous foil of Ni–7Cr–4.5Si–3.2B–3Fe alloy (AWS BNi-2) was used as the interlayer. Microstructure analyses were performed using optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Microhardness examinations and shear tests were performed to assess the effect of holding time on the mechanical behavior of dissimilar TLP bonded joints. The results indicated that the width of the athermally solidified zone was decreased with the increase of holding time at a constant temperature. The appearance of hardness peak values in the athermally solidified zone was due to the formation of eutectic compounds. Also, the shear strength was improved by increasing the bonding time. The TLP bonded joint fabricated at the bonding time of 45 min exhibited the best mechanical behavior due to the completion of isothermal solidification. Fractographic studies revealed that the fracture mode was completely ductile in the case of the joint made at the bonding time of 45 min.