Search

The multi-layer composite filler metal (YG18 surface pre-plated with Co layer + Ag–Cu–In–Ti filler metal) was designed in this study. The mechanism of modulation of Co-depleted zone and shear strength of joints by Co plating was elucidated. A more significant Co-rich layer existed around the WC particles, meanwhile, the presence of plastical Ag–Cu–In ternary eutectic between the Ti Co layer and the YG18/TiC layer relieved the joint stress and ensured that no cracks were generated in the Ti Co layer. Under the condition that the width of the Co-depleted zone was smaller (less than 3 μm), the presence of the dispersed Ti 2 Cu particles surrounded by the plastic phases ternary eutectic and Cu [s, s] in the filler layer was superior in terms of preventing crack propagation and absorbing the stress concentration. The best modulation of the filler layer microstructure and the Co-depleted zone was achieved when the pre-plated Co layer was around 2.5 μm. The Co-depleted zone was reduced by 50%, and the shear strength of joints was increased by 49% to 291 MPa. The results of the study provide a new way to design new multilayer composite filler metal. • The design of multi-layer composite filler metals (Co plating + filler metal) reduced the CDZ by 50% and increased the shear strength by 49%. • The presence of plastical ACI–TE between the TiCo layer and the YG18/TiC layer relieved the joint stresses. • The presence of the dispersed Ti 2 Cu particles surrounded by the plastic phases in the filler layer is superior in terms of preventing the cracks propagation and absorbing the stress concentration. [ABSTRACT FROM AUTHOR]

In this study, dissimilar YG18/40Cr joints were prepared using a Cu–Sn–Ti filled metal by a vacuum brazing process, and the microstructural evolution and bonding mechanism of the YG18/Cu–Sn–Ti/40Cr joints were studied. By adjusting the brazing parameters, the formation process of interface structure, the joint structure and matrix internal structure, and the changes in the joint microstructure and properties under different parameters were systematically analyzed. A TiC reaction layer was formed at the interface on both sides of the joint. The brazing performance can be improved by the formation of a reasonable size reaction layer. A TiC–WC cemented carbide was formed near the middle layer inside YG18, and this tenon–and–tenon structure improved the bonding between the YG18 side and the filler alloy. The connector structure was YG18/TiC/CoTi + Co 2 SnTi/Cu [s, s]/eutectic structure (Cu [s, s] + Cu Sn 3 Ti 5)/CuSn 3 Ti 5 /TiC/40Cr, and its eutectic structure changed as the parameters changed. The maximum average shear strength of the YG18/40Cr joint brazed at 940 °C for 5 min reached 216 MPa, which was ≈25% higher than the joint shear strength of the pure copper used in a previous study. The fracture morphology of the joint showed a large number of fossae and tear edges, indicating ductile fracture. • YG18 and 40Cr steel was brazed by Cu–Sn–Ti active filler metal, which filled the gap of low temperature brazing carbide with Cu-based filler metal. • A TiC reaction layer was found at the interface of YG18/filler metal and filler metal/40Cr, resulting in the high strength of this joint. • WC-TiC was obtained in the near-filled alloy region of the YG18 matrix, which was expected to improve the wear resistance of YG18 matrix while improving the metallurgical bonding. [ABSTRACT FROM AUTHOR]

It is crucial to design a novel active filler metal for brazing WC–Co cemented carbide–steel joints at low temperatures. In this study, we designed a low-melting-point multi-component active filler metal (Ag–Cu–Sn–Ti) based on Ag–Cu–Ti filler metal to achieve perfect combination of WC–Co/40Cr steel joints. The interfacial microstructure of the WC–Co/40Cr steel joint was comprehensively characterized, and the joint-bonding mechanism, mechanical properties, and fracture behavior after brazing at 700–780 °C were systematically analyzed. On both sides of the filler metal, WC and α-Fe combined with the TiC layer, enhancing the bonding of the filler metal to base materials. The typical structure of the joint is WC–Co/TiC layer/Co 2 SnTi + Cu–doped Cu 81 Sn 22 + Ag [s, s] + Ti–Cu granules/TiC layer/40Cr. The maximum shear strength of 241 MPa was obtained when the joint was brazed at 740 °C for 10 min, which is approximately 50% higher than those of previous low-temperature vacuum-brazed WC–Co/steel joints. The main factors leading to premature failure of joint include the distribution of phases in filler metal layer and defects of WC–Co caused by Co diffusion. • Designed a novel multicomponent active filler metal for application. • The microstructure of the WC–Co/Ag–Cu–Sn–Ti/40Cr joint was characterized and the connection mechanism was analyzed. • On both sides of the filler layer, WC and α-Fe combined with the TiC reaction layer. • The cost of filler metal is reduced and the shear strength of WC–Co/steel joint with low-temperature brazing is improved. [ABSTRACT FROM AUTHOR]

WC–Co cemented carbide/steel brazed at low–temperature is of significant scientific and technical interest. In this study, the interface microstructure between the filler alloy and WC–Co and 40Cr steel, the formation process of the joint microstructure, and the effect of brazing temperature on the microstructure and properties of joints were systematically studied. The filler alloy was bonded by forming a TiC reaction layer with WC–Co and 40Cr steel, which enhanced the retention of the filler layer on the joint. The microstructure of the joint was a WC–Co/TiC reaction layer/TiCo reaction layer/Cu 2 InTi + eutectic structure (Ag [s, s] + Ag–doped Cu 7 In 3 + Cu 4 In) + Cu [s, s]/TiC reaction layer/40Cr steel. Moreover, the maximum average shear strength of the joint (brazed at 740 °C) reached 258 MPa, which is approximately 60% higher than those reported in the literature. The fracture behavior of the joint was mainly affected by the distribution of the Cu 2 InTi intermetallic compounds in the filler layer and the diffusion of Co from the cemented carbide. • WC–Co cemented carbide and 40Cr steel was brazed at low–temperature (700–780 °C) with Ag–Cu–In–Ti filler alloy. • TiC reaction layer was formed at the interfaces of WC–Co/filler alloy and 40Cr steel/filler alloy after brazed, ensuring the perfect combination of the interface. • The maximum average shear strength of the joints (brazed at 740 °C) can reach 258 MPa, which is enhanced approximately 60%. • The joint dependence of fracture behaviors on joint microstructures was clarified. [ABSTRACT FROM AUTHOR]

YG18 cemented carbide and 40Cr steel were brazed using Ag–Cu–Ti filler metal under vacuum, and the microstructural evolution of the YG18/Ag–Cu–Ti filler metal/40Cr steel brazed-joint interface was investigated to determine how brazing temperature affected the brazed-joint microstructure, bonding strength, and fracture behavior. At the YG18 cemented carbide/filler metal interface, Ti atoms in the filler metal and C atoms in the YG18 cemented carbide formed a continuous TiC layer, reducing the difference in thermal expansion coefficients between the YG18 cemented carbide and filler metal. At the 40Cr steel/filler metal interface, Ti atoms in the filler metal and C atoms in the 40Cr steel formed a continuous TiC layer, preventing the diffusion of Fe atoms to the cemented carbide side and formation of a hard, brittle phase. YG18 cemented carbide/TiC/Cu 2 Ti/Ag–Cu eutectic + TiCu granules/TiC/40Cr steel-brazed joints were obtained. With increasing brazing temperature from 860 to 920 °C, the bonding strength of the YG18 cemented carbide/40Cr steel joint initially increased and then decreased. The joint brazed at 900 °C for 10 min failed in the middle of the brazing seam, and its average bonding strength was 235 MPa. • The connection of YG18 cemented carbide and 40Cr steel with Ag–Cu–Ti filler metal was prepared by vacuum brazing. • At the interface between the YG18 carbide and filler metal, a continuous layer of TiC was obtained, resulting in the reduction of the difference in the thermal expansion coefficient (CTE) between the YG18 cemented carbide and filler metal. • At the interface between the 40Cr steel and filler metal, the formation of a continuous layer of TiC prevented Fe atoms from spreading to the cemented carbide side to avoid the formation of a hard brittle phase. • The joint brazed at 900 °C for 10 min failed in the middle of the brazing seam, and its average bonding strength was 235 MPa. [ABSTRACT FROM AUTHOR]