Microstructure and compression properties at 1000?–1200°C of heat resistant nickel base superalloys heavily alloyed with γ'-forming elements

摘要

Experimental nickel base superalloys heavily alloyed with γ'-forming and substitution elements, have been studied in the present work from the viewpoint of their potential use as materials for manufacturing of isothermal die unit and milling tool intended for hot working of the most heat resistant nickel base superalloys at temperatures of 1100?–1200°C.?As the reference alloy, the heat resistant superalloy based on the intermetallic γ'(Ni3Al) phase having the composition near the same as the Russian superalloy VKNA-4 was also taken. The microstructure examination of the new nickel base superalloys revealed a high volume fraction (≥70?%) of the γ'-phase. At that in one of the superalloys primary coarse γ'-phase not dissolving at heating up to 1350°C caused by excessive alloying with γ'-forming elements was detected. The compression tests have demonstrated that the novel nickel base superalloys showed higher yield strength values in the temperature range of 1000?–1200°C as compared with those of the reference alloy based on the intermetallic γ'(Ni3Al)-phase. For instance the novel nickel base superalloys had the yield strength values at 1200°C as high as 165?and 140?MPa against 110?MPa obtained for the γ'(Ni3Al) based superalloy. The comparison with the literature data also confirmed that the new superalloys had higher or comparable yield strength values in the temperature range of 1000?–1200°C as compared to known VKNA superalloys. The performed work showed that the experimental nickel base superalloys can potentially be used for manufacturing of die and roll-forming tool intended for forming at 1100?–1200°С?the most heat resistant nickel base superalloys applied for producing discs for gas turbine engines.