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Nb-24Ti-18Si-2Al-2Hf-4Cr and Nb-24Ti-18Si-2Al-2Hf-8Cr alloys were prepared by arc melting in a water-cooled crucible under argon atmosphere.Microstructural characteristics and oxidation resistance of the alloys at 1250 ℃ were investigated.The results show that,when the Cr content is 4 at%,the microstructures consist of(Nb,Ti)_(ss) and Nb_5Si_3;as Cr content increases to8 at%,C14 Laves phase Cr_2Nb is formed.The isothermal oxidation tests show that the oxidation kinetics of the two alloys follow similar features.The weight gains of the two alloys after oxidation at 1250℃ for 100 h are 235.61 and198.50 mg·cm~(-2),respectively.During oxidation,SiO_2,TiO_2,Nb_2O_5 and CrNbO_4 are formed at first.Then,Ti_2Nb_(10)O_(29) is formed after oxidation for 20 min and begins to change into TiNb_2O_7 as the oxidation proceeds.SiO_2 is formed as solid state at first but later evolves into glassy state to improve the cohesion of the scale.After oxidation for 100 h,oxidation products consist of SiO_2,TiNb_2O_7,Nb_2O_5 and CrNbO_4.
Nb-24Ti-18Si-2Al-2Hf-4Cr and Nb-24Ti-18Si-2Al-2Hf-8Cr alloys were prepared by arc melting in a water-cooled crucible under argon atmosphere. Microstructural characteristics and oxidation resistance of the alloys at 1250 ° C were investigated. The results show that when the Cr content is 4 at%, the microstructures consist of (Nb, Ti) _ (ss) and Nb_5Si_3; as Cr content increases to8 at%, C14 Laves phase Cr_2Nb is formed. oxidation tests show that the oxidation kinetics of the two alloys follow similar features. The weight gains of the two alloys after oxidation at 1250 ° C for 100 h are 235.61 and 198.50 mg · cm -2, respectively. , TiO_2, Nb_2O_5 and CrNbO_4 are formed at first.Then, Ti_2Nb_ (10) O_ (29) is formed after oxidation for 20 min and begins to change into TiNb_2O_7 as the oxidation proceeds.SiO_2 is formed as solid state at first but later evolves into glassy state to improve the cohesion of the scale. After oxidation for 100 h, oxidation products consist of SiO _2, TiNb_2O_7, Nb_2O_5 and CrNbO_4.