Stefaniv B. Development of cadmium-free brazing filler metals and technology for brazing of mining tools to diamond - hard alloy plates.

The thesis is dedicated to the problem of development of cadmium-free brazing filler metals based on the Ag-Cu-Zn system, and state-of-the-art high-productivity rock-cutting tools for drilling of wells to produce diffuse methane. It was established that palladium exerts a substantial effect on formation of structure and properties of alloys of the Ag-Cu-Zn-Ni-Mn system, and at a content of 5 wt. % it increases strength properties of the brazed joints from 250 to 350 MPa. It was concluded on the basis of generalisation of a series of the tests that the most promising filler metals are those of the Ag-Cu-Zn-Sn-Ni-Mn and Ag-Cu-Zn-Ni-Mn-Pd systems. Specifications were worked out for manufacture of filler metals of the Ag-Cu-Zn-Ni-Mn-Pd system. The resulting experimental batches of the filler metals were used to manufacture full-scale products. The up-to-date technology for manufacture of drill bits by using DHAC and new designs of the domestic drill bits were developed (V.N. Bakul Institute for Superhard Materials, NASU). Owing to the application of the new technology the headway per bit was increased from 80-120 to 400-500 m. This is a good result for the said diamond - hard alloy cutters, although it is much lower than the corresponding indices of foreign analogues. Indices of the headway at a level of foreign analogues (up to 2000 m) were obtained after changing to foreign diamond - hard alloy cutters and optimisation of designs of the bits and calibrators.