摘要
以Ti-B4C-C为反应体系,利用自反应喷射成形技术制备了Ti(C,N)-TiB2复合陶瓷坯件。通过热力学分析,并结合水淬熄试验、DSC-TG、XRD及SEM等实验方法研究了喷射复合粉在自反应喷射成形过程中的反应转化机理。研究表明,复合粉在火焰场作用下温度迅速升高。温度升至536℃时表面部分的B4C开始被氧化;约882℃时,Ti由α相向β相转变,与此同时Ti的氧化与氮化反应也开始发生;至1085℃时,复合粉表面部分Ti的氧化与氮化及B4C的氧化基本完成。在1085℃之后,低熔点氧化产物B2O3的挥发及C的氧化损失令体系失重。1265℃时部分复合粉内部发生Ti、C间的固态扩散反应;1660℃时Ti开始熔化,复合粉内部因大量液相的出现,主反应开始剧烈发生,生成TiC与TiB2,其中前者与Ti的氮化产物TiN发生固溶反应生成稳定的TiC0.3N0.7固溶体。反应物不断消耗而产物相含量逐渐增多。C的氧化损失使复合粉内Ti部分过量,这部分Ti在喷射沉积过程中由于与基体碰撞、变形、铺展后增大了与空气的接触面积而被氧化为TiO2,残留在喷射沉积坯件内。
Ti（C,N）-TiB2 composite ceramic preforms were prepared by self-reactive spray forming technology taking Ti-B4C-C as raw reactive materials. The reactive transformation mechanism of the composite powders during the self-reactive spray forming process was studied by thermodynamics analysis, as well as the methods of water-quenching tests, DSC-TG, XRD and SEM. The results show that the temperature of the composite powders rises rapidly under the function of oxyacetylene flame. When it arrives at 536 ℃, B4C on the surface of the composite powders begins to be oxidized. At 882 ℃, solid phase transformation of Ti from α to β takes place. And almost at the same time, the oxidation and nitridition reactions of Ti start, too. When the temperature rises to as high as 1085 ℃, the oxidation and nitridition reactions finish. And over 1085 ℃, the volatilization of B203 and the oxidation of C lead to the weight loss of the system. At 1265 ℃, the atom diffusion in the composite powders has been intensified, which leads to the local solid diffusion reaction between Ti and C. At 1660 ℃ Ti begins to melt. Because of the intensive atom diffusion owing to the heat accumulation and the presence of abundant liquid titanium, the main reaction of the reactive system takes place intensively, which makes the desirable phases TiC and TiB2 appear. The solution reaction between TiC and TiN, which is the product of nitridition of titanium and forms the stable TiC0.3N0.v solid solution. Subsequently, the main reactions and side reactions in the composite powders make the reactants consume and products content increase gradually. The loss of B4C and C for the oxidation makes Ti in the composite powders excessive. This part of Ti will be oxidized into TiO2 and remains in the preforms during the spray deposition process for it increases the contact area with atmosphere after it bumps into and spreads on the substrate.
出处
《热加工工艺》
CSCD
北大核心
2008年第12期26-29,114,共5页
Hot Working Technology
基金
国家自然科学基金资助项目(50672130)
军械工程学院科研基金资助项目(YJJXM0608)
关键词
自反应喷射成形
复合粉
反应转化
机理
self-reactive spray forming
composite powders
reactive transformation
mechanism
