高密度纯钨的低温活化烧结工艺及其致密化行为

采用溶胶喷雾干燥-煅烧-氢热还原法制备了BET粒径为0.21μm的超细纯钨粉末,并利用球磨处理进一步活化粉末。研究了超细纯钨粉末形貌及其性能随球磨时间的变化特征,探索了未球磨、球磨5h及球磨10h3种超细纯钨粉末烧结致密工艺,此外还详细研究了纯钨烧结体组织形貌、晶粒尺寸及显微硬度等性能随烧结温度及球磨时间的变化规律。结果表明,球磨处理对超细纯钨粉末的烧结起到了极大的活化作用,由球磨10h粉末制成的压块在1900℃下烧结2h其致密度即可达97.3%,比传统微米级纯钨粉末制成的压块达到相同烧结致密度的温度降低了600℃以上。同时,球磨处理可以大幅降低钨粉的起始烧结温度和再结晶温度,获得组织更加均匀细小、力学性能(硬度)更加优良的钨烧结体。

Low-Temperature Activated Sintering Technology of High-Density Pure Tungsten and Its Densification Behavior

The superfine pure tungsten powder with a BET particle size of 0.21 μm was prepared by sol spray drying-calcination-hydrogen reduction process, and then it was treated by ball-milling activation. The changes of the morphology as well as other performance characteristics of the superfine pure tungsten powder with the increasing of ball-milling time were investigated, the sintering densification technologies of the as-received powder, the powders ball-milled for 5 h and 10 h, respectively, were explored. Additionally, the rules of properties changes such as the microstructure morphology, the grain size and the microhardness of the pure tungsten sintered body with sintering temperature and ball-milling time were studied in detail. Results show that the ball-milling treatment plays a great activation role in sintering of the superfine pure tungsten powder. When the green compact prepared by the powder milled for 10 h is sintered at 1900 °C for 2 h, the relative density of the sintered compact can reach 97.3%, the sinter temperature reduces by more 600 °C compared to that required for sintering the traditional micro scale powder compact. At the same time, ball-milling treatment can reduce the onset sintering temperature as well as recrystallization temperature substantially, so the sintered tungsten compact with much uniformer and finer microstructure and much better mechanical properties (hardness) can be obtained.