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7192 |
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Wednesday, June 22, 2022, Saal Brüssel 1:40 PM Brazing of demanding materials and joints |
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Potential of maraging steel as a joining partner for cemented carbide |
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Tim Ulitzka* / Dortmund University of Technology, Germany Wolfgang Tillmann / Institute of Materials Engineering, Germany Henrik Ulitzka/ Dortmund University of Technology, Germany Leif Dahl/ Sandvik Coromant AG, Sweden Lukas Wojarski/ Institute of Materials Engineering, Germany |
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Commonly cemented carbide-steel joints are manufactured by brazing processes with a local heat input like induction or laser brazing using a pre-heat treated and hardened tool steel component. Characteristic for these joining processes are the generally undesired microstructural changes in the tool steel joining partner in the vicinity of the brazed joint which can lead to an embrittlement and a softening effect of the applied steel in dependence of the heat exposure. Consequently, when cemented carbide-steel joints are manufactured by a vacuum brazing process, the steel is holistically exposed to the occurring process temperatures and its heat treatment needs to be integrated into the brazing process, in order to supply controlled and elevated mechanical properties of the steel component while at the same time guaranteeing a high quality of the brazed joint. This publication examines the possibilities of the maraging steel grade 1.2709 as a joining partner for cemented carbide in a vacuum brazing process. Due to the applied comparable low cooling rate of 5 K/min from the brazing respectively solution annealing temperature of 815 °C, which is possible because of the hardening mechanism, more precisely the lath martensite formation of the maraging steel 1.2709 almost independent from the cooling rate, shear strength values of more than 150 MPa were achieved while at the same time supplying an elevated and homogenous hardness of 420 HV1 of the steel component. In order to establish an acceptable wettability of the difficult to wet maraging steel, the active filler metal Ag65Cu28Sn5Ti2 as well as an additional 5 µm thick nickel coating of the maraging steel joining surface were evaluated. |