Processisng and Oxidation Behavior of Nb-Si-B Intermetallics.

Technical Information Center Oak Ridge Tennessee

关键词: Niobium borides;    Oxidation;    Powder metallurgy;    Silicon borides;    Glass;   

RP-ID  :  DE2005832901

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

Single phase materials of (alpha)-Nb(sub 5)Si(sub 3), Nb(sub 5)(Si,B)(sub 3) (T2) and Nb(sub 5)Si(sub 3)B(sub x) (D8(sub 8)) in the Nb-Si-B system were prepared by powder metallurgy processing. T2 was almost fully dense, while (alpha)-Nb(sub 5)Si(sub 3) and D8(sub 8) were porous after sintering at 1900 C for 2 hours. The lattice parameters of T2 decreased linearly with the substitution of B for Si. Isothermal oxidation testing at 1000 C in flowing air indicated that the oxidation resistances of T2 and D8(sub 8) are much better than (alpha)-Nb(sub 5)Si(sub 3), but still extremely poor compared to the boron-modified Mo(sub 5)Si(sub 3). Extensive cracking in the oxide scale and matrix were observed and arose from the volume expansion associated with the formation of Nb(sub 2)O(sub 5) and boron-containing silica glass.