DISTRIBUTION OF ALLOYING ELEMENTS IN THE STRUCTURE OF HEAT-RESISTANT NICKEL ALLOYS IN SECONDARY CARBIDES

Abstract

The use of X-ray spectroscopy is considered in studying the specific distribution of alloying elements in the structural components of heat-resistant nickel alloys, namely between secondary carbides, since the role of carbides in the formation of the properties of these alloys is complex. The theoretical modeling of thermodynamic processes of separation of excess phases using the CALPHAD method in the JMatPro software shell is carried out. Also, the structure and distribution of chemical elements in carbides depending on the alloy alloying are studied using a scanning electron microscope REM-106I. It is established that in typical M₂₃C₆ and M₆C carbides for the ZhS6K alloy, there is a tendency to degenerate phase reactions depending on the level of doping by the given elements. The mathematical dependences of the influence of the alloy alloying on the temperature of carbide separation (dissolution) and changes in the chemical composition of the alloy on the content of elements in the carbides are established. When the content of chromium is increased, the M₆C carbide gradually degenerates and disappears at 11 mas.%. When the molybdenum content in the alloy is 3 mas.%, a topologically tightly packed TSH phase in the structure is formed, while at 8 mas.% Mo, M₆C carbide approaches the molybdenum-based monocarbide. The dependences of the temperatures of separation (dissolution) of the carbides on the amount of tungsten content in the alloy are calculated. An increase of tungsten in the alloy was found to increase the temperature of releasing (dissolution) of all carbides in the alloy. At a concentration of 11 mas.% in the tungsten alloy, the TSH phase is released, which negatively affects the properties of the system under study. The obtained dependences were experimentally confirmed using X-ray spectroscopy on the heat-resistant nickel-based alloys ZhS6K. The stoichiometric formulas of the carbides were calculated, the theoretical and practical results were compared and their agreement was established.