| Ni-base superalloy has excellent mechanical properties and oxidation resistance at elevated temperatures, it is widely used in aviation and space, petroleum and chemical industry. In this paper, the effect of the cold crucible levitation melting (CCLM) on K4169 alloy and the Al,Ti content of K418 alloy on the microstructure and properties was respectively studied, and the thermodynamic data of several Ni-base superalloy were calculated, the structure and properties of four Ni-base alloys designed by d-electron orbit theory were analysed. The results are as follows:(1) The differences of microstructure and properties of K4169 alloy by CCLM and VIM(vacuum induction melting) were studied. The results show that the cooling rate of K4169 alloy by CCLM is faster than by VIM, dendrite of as-cast alloy is more obvious, and there exist large blocks of Laves phase, the tensile and compressive strength are respectively 56% and 25% higher than that by VIM, the dendrite structure of tensile fracture is obvious; Laves phase in the alloy is fine dispered after heat treatment, compared with as-cast alloy, the tensile strength of the alloy is increased by 19%, the plasticity and the compressive strength are decreased.(2) The effect of Al element on the microstructure and properties of K418 alloy was studied. The results showed that interdendritic y’phase content increases with the increase of Al, tensile and compressive strength also increase, ductility decreases; there are obvious grain boundaries in the alloy after heat treatment and strengthening phase is obvious, and when Al is 7.3wt.%, Laves phase appears in alloy specimens and strength is minimum, when Al is 6.4wt.%, strength of alloy is highest, the dendrite structure of the tensile fracture gradually decreases.(3) The effect of Ti element on the microstructure and properties of K418 alloy was studied. The results show that y’phase and the tensile strength of the as-cast alloy both increases with the increase of Ti; grain boundary and strengthening phase appear obvious after heat treatment, when Ti is lwt.% microstructure appears round oxides, when Ti is 0.75wt.%, the strength of alloy decreased.(4) The effect of Al/Ti ratio and Al+Ti content on the microstructure and properties of K418 alloy was studied. The results show that the tensile strength of the as-cast alloy is dominated by the total amount of Al+Ti, and intensity would increase with the growing of the total amount of Al+Ti in a certain range; Al/Ti ratio of the alloy is dominant after heat treatment, lower Al content is beneficial to improve its tensile strength.(5) The thermodynamic data of several typical Ni-base superalloys were studied, and four kinds of nickel based alloy was designed by using d-electron orbital theory, their microstructure and properties were analysed. Results show that melting temperature of the common nickel base alloys distribute between 1200-1380 ℃ and y’phase volume fraction is around 60% at 850 ℃; 1#～3# as-cast alloy in four kinds of alloys exist dendrite structures, γ’is the main existing phase after heat treatment, as-cast tensile strengths are 1054MPa,916MPa and 892MPa respectively, and 2# alloy plastic is larger,4# alloy exists more loosen tissues and segregation is serious, its strength is largest, but plastic is poor, only as a contrast group to the others. |
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