Авіаційно-космічна техніка та технологія (Aug 2022)
Morphology and topogtaphy of carbide phase after alloying with hafnium and tantalum the ZHS3DK-VI
Abstract
This study describes the results of studying the effect of modification/micro alloying with hafnium and alloying with tantalum on the morphology and distribution of the carbide phase in the ZhS3DK-VI alloy microstructure. The carbide phase is an integral structural component of the microstructure of nickel heat-resistant alloys, has a tremendous impact on the strength characteristics of the material. In this regard, the shape, size, and distribution of particles of this phase in the microstructure are of great importance. The formation of the morphology of carbide particles largely depends on the technological factors of casting such as temperature of the ceramic mold, crystallization rate, melt temperature, etc. The higher the temperature parameters and the lower the crystallization rate during casting, the coarser the morphology and topography of carbide particles formed during solidification and, accordingly, the lower the strength characteristics of the material. However, technological parameters also affect the geometry of the casting and it is not always possible to change the technology; so the only possibility is the use of modification or alloying of the alloy upon receipt of the work piece. Such carbide-forming elements as hafnium and tantalum, due to their chemical activity, react with carbon at the stage of crystallization and form thermally stable primary MC-type carbides. The use of hafnium in nickel alloys is limited to a concentration of 0.1 % since at a higher concentration, this element and nickel form a eutectic phase, the melting temperature of which is much lower than the homogenization temperature of the alloys. It is studied the possibility of doping the ZhS3DK-VI alloy with tantalum to form a favorable morphology of the carbide phase. The dispersed carbide particles are taken in the microstructure of the ZhS3DK-VI alloy after experimental work. The chemical composition of the particles is dominated by tantalum, and there is some hafnium.
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