PROTECTIVE TECHNOLOGICAL COATING BASED ON ZrO2–BaO–B2O3–SiO2 SYSTEM FOR PROTECTION OF HEAT-RESISTANT NICKEL ALLOY WITH SINGLE-CRYSTAL STRUCTURE DURING HEAT TREATMENT

Abstract

The purpose of this work was developing of protective technological coating for protection of heat-resistant nickel alloy with single-crystal structure ZHS30 during high-temperature homogenization. Based on characteristics of the alloy the synthesis of coatings was carried out in following directions: modification of known coatings in the system CaO–BaO–SiO2 by introducting refractory filler and organosilicon materials, research of two-layer coatings and synthesis of refractory frits in various silicate systems. The best properties of alloy ZHS30 are obtained using a coating based on a synthesized frit containing SiO2, B2O3, BaO, ZrO2. High efficiency of the protective action of the coating is ensured by the chemical composition of the frit which leads to the formation of structural groups [BO4] in the glass that participate in the formation of the glass lattice. Zirconium ions also participate in the construction of the structure and together with silicon and boron ions form a single boron-zirconium-silicon-oxygen framework of high degree of polymerization. The revealed liquation structure of the frit consists of two glass phases: the more easily low-melting matrix contains drop-like inhomogeneities distributed in it enriched of SiO2 which explains the steadiness and stability of the glass at operating temperatures.