A bonding technique for thermally and mechanically highly stressed joints between cemented carbide with low content of C0-binder, silicon nitride or boron carbide and steel shall be provided. The hard materials will be brazed to tools for mechanical machining.
Newly developed cemented carbide (CC), silicon nitride (SN) and polycrystalline diamond (PCD) have been brazed to low alloy steel for cutting tool applications. The properties of the hard materials were measured mainly for creating data for finite element method (FEM) calculations of residual stresses. Wetting tests with active filler metals have been carried out. Wetting and strength tests of joints with active filler metals showed good results. Very good results with SN were obtained by using a premetallization technique with active filler metal paste. FEM calculations were carried out on various specimen designs and on real tools. It can be shown that FEM methods are a very effective tool for optimizing the design and minimizing residual stresses. With all hard materials real components were brazed and tested.
Regarding thermal stresses, PCD tools are even more critical than CC and SN, and with PCD good results were also obtained using active filler metals.
The following tools have been successfully brazed and tested with CC and/or SN: profile cutter, edge bending cutter, peripheral cutter, extrusion die, circular saw, a special design of PCD tool.
It should be emphasized that especially for the circular saw, the premetallization technique with active filler metal paste showed good strength results. The premetallized SN tips were brazed with the copper interlayer filler metal L-Ag49/Cu which leads to good strength combined with very low residual stresses.
Suitable filler materials have to be developed which fulfil the objectives listed below :
- good wetting of newly developed cemented carbides, silicon nitride and boron carbide
- achieving shear strength of 200 MPa at room temperature
- the joints have to withstand service-temperatures of up to 600 degrees C.
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5600 MB Eindhoven