During high-temperature brazing processes with gap widths larger than 50 μm the undesired formation of brittle phases can occur. Formation of such brittle phases leads to a decreasing of the mechanical strength of the joint. In the case of nickel-based filler materials, brittle phases are formed primarily from silicon, phosphorus or boron which are used for alloying to decrease the melting point of the filler. By determining the diffusion coefficients of these specific elements as a function of the process temperature, brazing processes can be optimized to prevent the formation of brittle phases. With a low fraction of brittle phases, the mechanical strength of the joint can reach values comparable to those of the base material. The approach of optimizing the brazing process has proven to be successful for joints with base materials of the same and of different types. With the proposed procedure it is also possible to predict the amount of brittle phases that can be tolerated without decreasing the mechanical strength. Thus, the mechanical properties of the joint can be optimized considering the cost-efficiency of the process.
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