Effect of Carbides on NiAl Precipitates and Mechanical Properties in NiAl-precipitation-strengthened Ferritic Heat-resistant Steels

Traditional ferritic heat-resistant steel is mainly strengthened by carbides,while the new ferritic heat resistant steel is mainly strengthened by NiAl precipitates. The main factor of limiting the application of NiAl strengthened ferritic heat resistant steel is poor ductility at room temperature. In this study,by adding carbon content in NiAl strengthened ferritic heat resistant steel,the interaction between carbide and NiAl precipitates and the effect on the mechanical properties were studied. The results show that with the increase of carbon content,carbides increase,and the morphology of carbides at grain boundaries is transformed from discontinuous block-like to continuously distributed strip-like. The precipitation of carbides decreases the lattice misfit between α-Fe matrix and NiAl precipitates. The mean radius of NiAl precipitates decreases by 30 nm approximately,and the volume fraction slightly decreases. The hardness,strength and ductility of the steels are improved. The results provide fundamental guidance for the ductility improvement of NiAl strengthened ferritic heat-resistant steel. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.