DEVELOPMENT OF TECHNOLOGICAL RECOMMENDATIONS FOR THE FORMATION OF BORIED POWDER FOR PLASMA SPRAYING OF NICKEL ALLOY

Abstract

The article describes the choice of the method and medium for diffusion alloying of nickel alloy powders. One of the main and most effective ways to protect parts from high-temperature corrosion and oxidation is to create a nickel-based plasma coating system on their working surface. Their performance properties depend on the order of distribution of γ´ - and β - phases in the formed γ-solid solution. In the technologies for creating heat-resistant coatings based on nickel, a whole range of alloying materials (zirconium, tungsten, molybdenum, rhenium, hafnium, niobium, tantalum, vanadium, etc.) are introduced into these systems to further improve performance properties. They affect the thermal stability of the precipitates of the strengthening γ´ - phase. Carbon and boron are also introduced, promoting the formation of carbide and boride phases, increasing fracture toughness, creep time, and long-term strength period. Based on a number of advantages (simplicity, general availability, reliability of the technology, high stability of results, possibility of repeated use of the saturating medium) for diffusion saturation of powders based on nickel alloys in order to ensure high performance properties, the method of saturation in powder media of boron and silicon carbides was selected. It was found that from the point of view of ensuring the stability of the shell thickness, good fluidity and stability of the dispersion composition, the best ratio of the saturating medium to the saturated one is in the range of 4:1, the ratio in the saturating medium is B4C-SiC (40%:60%) with approximate equality of particle sizes and their size of 40-60 μm, and sodium fluorides in an amount of 1-1.5% are most suitable as an activator.