Ceramic-to-metal welding by a pressurized combustion reaction
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Osamu Yamada College of General Education, Osaka Industrial University, Daito, Osaka 574, Japan (Received 29 October 1985; accepted 10 January 1986) A new method of ceramic-to-metal welding has been developed using a pressurized combustion reaction to form Mo-TiB 2 -Mo and Mo-TiC-Mo couples. Mixtures of Ti powder with B or C between Mo disks were electrically ignited under 3 GPa pressure. The exothermic reaction of the powders resulted in the formation of TiB 2 and TiC and reaction with Mo at the metal interface. Weld strengths of the Mo-TiB 2 -Mo and Mo-TiC-Mo couples were 20-40 MPa and ~ 10 MPa, respectively.
A new method for ceramic-to-metal welding has been developed by applying a pressurized combustion reaction. Two welded couples of Mo-TiB 2 -Mo and Mo-TiC-Mo were prepared by electric ignition on a powdered mixture of Ti and B or C placed between Mo disks under 3 GPa. The mixed reactants were converted to sintered TiB2 and TiC, respectively, as a result of the combustion reaction, and the chemical reaction between the ceramic and the metal caused by the released high heat of combustion welded them. The new welding process conducted in the present study is illustrated in Fig. 1. A similar process is known as thermite welding and it utilizes the exothermic reaction of powdered Al and Fe2O3. Previous works have shown that the dense TiB^ and SiC2 could be fabricated by the high-pressure selfcombustion sintering (HPCS), which was developed as a combined process of the self-propagating high-temperature synthesis3-4 and the high-pressure technique. The HPCS can be used to synthesize and simultaneously sinter boride or carbide ceramics from their constituent elements in a very short time by stimulating strong exothermic reactions under high pressure. The pressurized combustion reaction is expected to be available not only for sintering, but for welding of ceramics. The joining of ceramics to metals or to other ceramics is of importance in order to attach ceramic components to an actual device, especially for use in engineering. The refractory metal Mo was used as the metal component, and TiB2 and TiC were chosen as the ceramic components. These ceramics are easily produced by the combustion reaction because of their high formation energies of 293 and 232 kJ/mol, respectively. The calculated adiabatic temperatures were about 2900 °C for both ceramics,5 which enable Mo to melt. The differences of thermal expansion coefficients between TiB 2 / J. Mater. Res. 1 (1), Jan/Feb 1986
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Mo and TiC/Mo are below 2xlO~ 6 &~ 1 from room temperature to 2000 °C.6 The fine powders of Ti with a particle size below 40 and amorphous boron for TiB2, or Ti and amorphous carbon for TiC, were well mixed in their stoichiometric ratios, respectively. Each mixed powder was press-formed to a thin disk that was 5.8 mm in diameter
Sandwiched with Mo
Welded couple Mo - TiB. - Mo Mo - TiC - Mo FIG. 1. Schematic of a new welding process utilizing the combustion reaction under high pressure.
0003-6951 /86/010007-03$0
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