Buturlia Y. Development of brazing filler and brazing technology of heat-resistant nickel alloys of new generation marine gas turbine blades

The work is devoted to a scientific and applied problem - the development of brazing filler metal for heat-resistant nickel alloys of the new generation (HNA). For marine gas turbine construction there has always been a problem of increasing the operating temperature and service life of turbines, which is complicated by the operating conditions of marine gas turbine engines (GTE). Marine GTE operate on heavy fuel with sulfur impurities and in conditions of high-temperature salt corrosion (HSC), the speed of which is hundreds of times higher than the corrosion rate in aircraft turbines. Alloys CM93-VI and CM96-VI were developed for the new generation turbines of Gas Turbine Research and Production Complex Zorya-Mashproekt and the Physics-technological institute of metals and alloys of the National Academy of Sciences of Ukraine, which allow to increase the operating temperature of the gas by 40… 60 ° С. The base and universal way of joining foundry HNA is brazing, which has the problem of increasing the heat resistance and longevity of high-temperature strength of brazed joints. Therefore, for the development of marine gas turbine construction, it is important to develop a brazing filler that will provide the necessary physical and chemical characteristics of the welded joint for new alloys. The aim of the dissertation research is to develop brazing filler and brazing technology of heat-resistant nickel alloys CM93-VI and CM96-VI for the production of new generation vascular gas turbines with increasing gas operating temperature and high temperature strength of brazed joints not less than 80% strength of the base metal. The scientific novelty may be that: 1. For the first time a two-stage method of brazing filler metal development is substantiated, the essence of which is that at the first stage, using computer programs, the brazing filler metal base is calculated with the inclusion of the most effective alloying elements providing solid-soluble and dispersion hardening. to prevent the formation of TDP phases, in particular the σ-phase, and in the second stage the required concentration of depressants is experimentally determined. 2. It was first established that multicomponent brazing filler metal from Re and Ta systems Ni-Cr-Co-Al-Ta-Re-W-Mo-Ti-Nb-B-Hf-Zr-C provide edge wetting angles of alloys CM93-VI and CM96-VI up to 6°, specific spreading area 1.4-1.5 mm2/mg at the temperature of soldering and correction of surface defects of castings 1200-1230 ° C. 3. The brazing filler metal alloying system has been improved, which provides long-term strength of CM93-VI and CM96-VI alloys at 900 °C at the level of 0.9 of the strength of the base metal. 4. Received a further development of the idea of the stress state of brazed joints with a interlayer of solder with its relative thickness (s/d from 0,0025 ... 0,01), which has different from the base metal physical and mechanical properties, which consists in because on most of the node in the main metal stresses are virtually absent under thermal load and linearly distributed under force load. In the outer surface of the joint and in the interlayer itself, a three-dimensional stress-strain state is formed, which leads to the strengthening or weakening of the base metal and the interlayer. The practical significance of the work includes: A two-stage theoretical and experimental method of brazing filler metal development using computer programs is proposed and implemented. Using the new method, SBM-4 brazing filler metal and brazing and correction technology for surface defects of industrial castings for heat-resistant nickel alloys CM93-VI and CM96-VI were developed. The brazing filler metal passed the Gas Turbine Research and Production Complex Zorya-Mashproekt, which showed the brazing temperature of 1215…1230 °С, long-term strength for brazed joints at 900 ° С at the level of 0.9 of the base metal level and resistance against high-temperature salt corrosion at the level of the alloy CM88U-VI. The brazing filler metal can be used for other HNA and was used to restore by brazing in vacuum damaged high-temperature elements of the equipment of heat-resistant alloy ChS88-VI to obtain centrifugal plasma spraying of spherical powders.