Transient Liquid Phase Bonding of 2205 Duplex Stainless Steel Using a Ni-P Interlayer

Abstract

Transient liquid phase (TLP) bonding was successfully applied to join 2205DSS using a Ni-P interlayer. Microstructural studies revealed that isothermal solidification (IS) progressed via formation of γ-Fe solid solution from the base metal (BM)/bonding zone (BZ) interface toward the BZ centerline. Cooling the TLP bonding assembly before completion of the IS resulted in non-isothermal solidification (athermal solidification: AS) of the residual liquid (L) along the BZ centerline. Microstructural studies revealed that the AS took place via L → γ-Fe + M3P eutectic transformation. FESEM/EDS and XRD analyses indicated that M3P was a complex (Fe,Ni,X)3P phosphide that X contained Cr and Mo elements. Formation of the phosphide constituents increased significantly the microhardness of BZ centerline (up to 510 ± 5HV) and resulted in sharp decrease of shear strength of the TLP-bonded specimen (180 MPa). Completion of the IS caused uniform microhardness profile across the BZ (~ 240 ± 5HV) and significant enhancement of shear strength of the TLP-bonded specimen (~ 380 MPa). Furthermore, pitting corrosion resistance of the TLP-bonded specimen increased significantly after completion of the IS, i.e., the weight loss of TLP-bonded specimen decreased to 0.39 mg/mm2 that was close to that of the as-received BM (0.23 mg/mm2).