摘要
使用不同种类催化剂(NaF,NH_4F,NH_4Cl,NaBr和NaCl)经1250℃保温8 h扩散共渗,在新型Nb-Ti-Si-Cr基超高温合金表面制备了Si-Zr-Y共渗层,分析了各共渗层的结构及相组成,并对其组织形成过程进行了讨论.结果表明:不同种类催化剂制备的共渗层由外至内均由(Nb,X)Si_2(X表示元素Ti,Cr和Hf)外层,(Ti,Nb)_5Si_4过渡层及富Al,Cr和Y的(Nb,X)_5Si_3内层组成.在5种催化剂中,采用NaF和NH_4F时制备的共渗层较厚、组织致密,且采用NaF时所制备的共渗层中Zr和Y的含量较高;采用NH_4Cl,NaBr和NaCl时制备的共渗层较薄且表面分布有大量的孔洞以及ZrO_2和HfO_2氧化物.渗包内Si的卤化物平衡气相分压较高时制备的共渗层较厚且组织致密;而Zr和Y的卤化物平衡气相分压对其在共渗层中的含量没有显著影响.
Si-Zr Y co-deposition coatings on an Nb-Ti-Si Cr base ultrahigh temperature alloy were prepared by pack cementation processes at 1250 ℃ for 8 h with different halide activators in the packs. The structure, constituent phases and formation process of the coatings were investigated. The results show that all the coatings are mainly composed of an （Nb, X）Si2 （X represents Ti, Cr and Hf elements） outer layer, a （Ti, Nb）5Si4 transitional layer, and an A1, Cr and Y rich （Nb, X）sSi3 inner layer located between the coating and the substrate. In the five kinds of （NaF, NH4F, NH4Cl, NaBr and NaCl） activators investigated, the coatings prepared respectively with NaF and NH4F activators are thicker and denser, and furthermore, the contents of both Zr and Y elements are larger in the coating prepared with NaF as the activator. However, the coatings prepared respectively with NH4Cl, NaBr and NaCl as the activators are thiner, and lots of holes and ZrO2 and HfO2 particles are observed in the surface layer of the coatings. The higher equilibrium partial pressures of gaseous halide silicides in the packs resulted in thicker and denser co-deposition coatings, while the equilibrium partial pressures of gaseous halide Zr and Y in the packs have less effect on their contents in the coatings.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第11期1394-1402,共9页
Acta Metallurgica Sinica
基金
国家自然科学基金项目50871087
高等学校学科创新引智计划项目B080401资助~~
