材料损伤HIP自愈合机理研究

目的研究金属注射成形烧结后内部缺陷自愈合方法。方法将热等静压(HIP)技术与金属注射成形(MIM)工艺结合,控制热等静压参数使得注射成形烧结后的内部缺陷产生自愈合。借助扫描电镜观察内部孔隙消除与缺陷的闭合情况,通过CAE仿真分析颗粒间应力变化,研究热等静压工艺(HIP)自愈合的机理,通过力学抗压试验测试HIP后力学性能。结果扫描电镜结果表明,内部孔隙与缺陷在HIP后完全消除,CAE结果表明,HIP自愈合过程主要是高温高压下的材料发生塑性变形流动机制与扩散蠕变机制起主导作用。力学性能结果表明,HIP后抗压强度提升21.47%,屈服强度提升28.91%,并且HIP后应变断裂点数值明显小于热等静压前。催化进度过程中,粉体内部聚甲醛气体分解挥发后,在零件的内部会形成多孔性结构,并且气体逃逸的通道形成了裂纹,造成烧结过程中厚壁件内部形成空隙与裂纹。结论热等静压后由金属注射成形烧结后形成的内部缺陷完全消除。随着研究的深入和完善,可为金属粉末成形零件的性能优化和广泛应用提供基础。

HIP Self-Healing Mechanism of Material Damage

The paper aims to explore a self-healing method of internal defects after sintering of metal injection. The thermal isostatic pressure (HIP) technology was combined with metal injection forming (MIM) process to control of thermal isostatic pressure parameters to realize self-healing of internal defects after injection forming. The internal pore elimination and defect closure were observed with scanning electron microscope. The stress changes between particles were analyzed by CAE simulation. The mechanism for self-healing of thermal isostatic pressure process (HIP) was studied. The mechanical properties of HIP were tested by mechanical compressive test. The result of SEM showed that the internal pores and defects were completely eliminated after HIP. The CAE results showed that the self-healing process of HIP was mainly dominated by the mechanism of plastic deformation flow and diffusion creep mechanism under high temperature and high pressure. The mechanical properties showed that the compressive strength of HIP was increased by 21.47%; the yield intensity was increased by 28.91%; and the strain fracture points after HIP were significantly less than that before thermal isostatic pressure. During the catalytic progress process, after the decomposition and evaporation of the polyformaldehydegas in the powder, a porous structure was formed inside the partcracks formed on the gas escape channel, resulting in voids and cracks inside the thick wall parts during the sintering process. After thermal isostatic pressure, the internal defects formed after sintering by metal injection are completely eliminated. With the further research and perfection, it can provide the foundation for the performance optimization and wide application of metal powder forming parts.