Si-Zr-B涂层结构稳定性及对DD3单晶高温合金深过冷的非催化形核惰性

 以 Si O2 玻璃粉、分析纯 Zr O2 粉为粉料,分析纯 C2 H5OH,Zr OCl2 · 8H2 O,去离子 H2 O与分析纯Si(OC2 H5) 4按 4∶ 0.1 1∶ 3∶ 1的摩尔比配制的前驱液经 3 5℃,1 80 min水解 -聚合反应后形成的 Si O2 -Zr O2溶胶为粘结剂,H3 BO3 为软化剂,用熔模制壳技术在壳型内壁制备了 Si-Zr-B基底涂层。利用溶胶 -凝胶原理,以 Si O2 -Zr O2 溶胶中加入 H3 BO3 形成的 Si O2 -Zr O2 -B2 O3 溶胶为原料,经浸涂 -分级热处理和 80 0℃玻璃化热处理后,在基底涂层表面制备了适宜厚度的同成分玻璃薄膜涂层。将涂层在 1 5 0 0℃保温 3 0 min后,XRD结果表明,涂层的析晶量仅为 1 %～ 3 %,具有很高的高温结构稳定性。过冷实验表明,DD3单晶高温合金可在该 Si-Zr-B涂层壳型内获得最大 1 4 0 K过冷度,完全可以实现深过冷快速凝固,证明 Si-Zr-B涂层具有良好的非催化形核惰性。

STRUCTURE STABILITY AND NUCLEATION INHIBITION ON THE UNDER-COOLED DD3 SINGLE CRYSTAL SUPERALLOY MELT OF THE Si-Zr-B COATING

Using the mixture of SiO 2 glassdust and ZrO 2 powder as refractory material, SiO 2-ZrO 2 sol as binder and H 3BO 3 as softening agent, a substrate layer was prepared on the inner surface of the mold by adopting shell-molding technique, where the SiO 2-ZrO 2 sol was the product of the hydrolyzing-condensation reaction at 35℃ for 180 min in the precursor solution with the mole ratio of 3H 2O, 4C 2H 5OH, 0.11 ZrOCl 2·8H 2O and 1 Si(OC 2H 5) 4, respectively. Then adopting sol-gel processing, proper layers of SiO 2-ZrO 2-B 2O 3 thin film with the same composition as the substrate layer was compounded with the substrate layer step by step. After dipping-class heat treatment and glassing treatment at 800℃ for 60 min, this film transformed into the SiO 2-ZrO 2-B 2O 3 glass coating. Furthermore, after holding the coating at a temperature of 1500℃ for 30 min, the amount of crystalline is about 1%~3%(vol%). Finally, an undercooling experiment showed that high undercooling of DD3 single crystal superalloy up to 140K was achieved in this coating mold. Based on the classical nucleation theory, the wetting angle corresponding to the largest undercooling achieved in the inhibitive coatings, θ*, was calculated. It is found that they are far less than the measured one between coating and alloy melt. This phenomenon further proves that not only the SiO 2-ZrO 2-B 2O 3 coating has good high-temperature structure stability, but also it is an ideal inhibitive nucleation coatings for DD3 single crystal superalloy melt.