Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal
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JMEPEG DOI: 10.1007/s11665-016-2424-6
Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal X.Z. Zhang, G.W. Liu, J.N. Tao, H.C. Shao, H. Fu, T.Z. Pan, and G.J. Qiao (Submitted May 30, 2016; in revised form October 18, 2016) The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/ SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers. Keywords
cememted carbide, interface, joining, mechanical property, steel, wetting
1. Introduction Tungsten carbide/cobalt (WC-Co) cemented carbides, consisting of large volume factions of WC particles embedded in the soft and ductile Co binder, can serve as hard and tough tool material (Ref 1). Due to the good compatibility of the hard WC grains and the ductile Co binder phase, the WC-Co cemented carbides show high hardness, strength, refractoriness, as well as compressive deformation and wear resistances. These good mechanical properties make the WC-Co cemented carbides be typically used as drilling or cutting tools, structural components, mining bits and press molds, as well as miniature drills for highly integrated printed circuit boards or rock drills (Ref 25). However, the widespread use of cemented carbides is limited by their expensive cost and brittleness. The joining of cemented carbides to structural steel has received much attention in recent years because of the compensatory properties. Presently, their joining techniques are mainly composed of brazing (Ref 6-13), diffusion bonding (Ref 14-16), fusion welding (Ref 17, 18) and partial transient liquid-phase bonding (Ref 19), among which brazing is an appropriate process to join X.Z. Zhang, J.N. Tao, H.C. Shao, and H. Fu, School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China; G.W. Liu, School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China; and Suzhou Pant Piezoelectric Tech Co. Ltd., Suzhou 215300, China; T.Z. Pan, Suzhou Pant Piezoelectric Tech Co. Ltd., Suzhou 215300, China; and G.J. Qiao, School of
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