多层壁陶瓷型芯内腔熔芯的制备及性能研究

Fabrication and properties of a fusible core as the inner cavity of multi-layer ceramic core

采用预制夹芯法制备多层壁陶瓷型芯因具有工艺简便、成型精度高等优点受到关注。笔者以聚乙二醇(PEG)为增塑剂,石墨、石英玻璃粉为填料,制备了可熔夹芯;通过二次注射成型制备了多层壁陶瓷型芯坯体,实现了熔芯/型芯的一体脱脂。研究了聚乙二醇分子量对熔芯浆料及制备坯体性能的影响,结果表明:当PEG分子量不超过2 000时,增塑剂分子量对熔芯性能的影响较小,随着PEG分子量继续增加,坯体内缺陷增加导致性能变差;采用PEG2000制备的熔芯坯体具有最佳的综合性能,其抗弯强度、高温变形量和表面粗糙度分别为13.0 MPa、2.94 mm和1.18μm。研究了熔芯/型芯的一体化脱脂行为,经过脱脂和烧结,熔芯被完全烧蚀,形成了陶瓷型芯的空腔结构,且熔芯脱除对陶瓷型芯的结构完整性和精度未产生不良影响。陶瓷型芯制件的尺寸公差不超过±0.15 mm,空心内腔表面粗糙度为1.81μm,满足高温浇铸对陶瓷型芯尺寸精度的要求。

The prefab-core method is favored in the fabrication of multi-layer ceramic cores for its advantages of process simplification and cost reduction. As the inner cavity of a ceramic core, a fusible core was prepared in this research with polyethylene glycol(PEG) as the plasticizer, graphite and quartz glass powder as the fillers. The ceramic core was prepared by secondary injection molding method, and co-debinding with fusible core was achieved. The effects of molecular mass of PEG on the properties of fusible core slurry and green body were studied. The results showed that the molecular mass of PEG played a minor role when molecular mass was less than 2 000, yet the performance of the green body would become poor due to increased defects when the molecular mass exceeded 2 000. That is to say, the fusible core prepared with PEG2000 had the best performance: the flexural strength, heat deflection and surface roughness of the fusible core were 13.0 MPa, 2.94 mm, and 1.18 μm, respectively. The co-debinding behavior of the ceramic core/fusible core was also investigated. After debinding and sintering, the fusible core was burned out and the inner cavity of multi-layer ceramic core was formed. The structure integrity and dimensional accuracy of the ceramic core were not influenced by the removal of the fusible core. The dimensional accuracy and inner surface roughness of ceramic core were less than ±0.15 mm and 1.808 μm, respectively, which met the requirements of high temperature casting.