Авіаційно-космічна техніка та технологія (Aug 2022)
Effect of complex modification on properties and structure of nickel super alloy
Abstract
In this work, a study of the influence of complex modification of the ZhS3DK-VІ nickel-based heat-resistant super alloy was conducted. The modification was performed out according to different technological schemes: with highly dispersed titanium carbonitrides Ti[Ti(C,N)] particles, with Ti [Ti(C,N)]+CoAl2O4 and Ti[Ti(C,N)]+CoAl2O4+Ni-Y complex that made it possible to investigate the specifics of the influence of the volume modifier Ti[Ti(C,N)] separately, and its complex effect with surface modifierCoAl2O4 and rare earth metals (with Ni-Y master alloy use) in the macro- and microstructure of a heat-resistant nickel alloy. It was shown that the use of modifiers allows for significant refining of macrograins, and the greatest effect was obtained with Ti[Ti(C,N)]+CoAl2O4 and Ti[Ti(C,N)]+Ni-Y+CoAl2O4complexes. Microstructure study allows to show that the value of interdendritic distances in both the case of modification with Ti[Ti(C,N)] and Ti[Ti(C,N)]+Ni-Y+CoAl2O4 complexes essignificantly decreased, from 100…130 μm to 80...120 μm, which is the result of many nuclei formation during crystallization in the volume of the alloy and with highly intense heat transfer from the melt by CoAl2Omodified ceramic mould after melt pouring. Based on the results of the influence of various types of modification on the microstructure of the alloy under study, it was established that modification according to all schemes allows obtaining carbides of smaller sizes, but grown sizes of carbonitrides was observed. Globular particles of carbide and carbonitrides are evenly located along the cross-section of the samples under study. In all cases of modification, a decrease in the value of the shrinkage microporosity was observed. The mechanical properties of the specimens after standard heat treatment shows, that modification with complexes under study allows provide mechanical properties that meet the specification requirements. The best complex of alloy mechanical properties at room temperature, fracture toughness and stress-rupture strength provides with Ti[Ti(C,N)]+Ni-Y+CoAl2O4 modifiers complex.
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