选区激光熔化用高强合金钢粉末制备及其成形性研究

Preparation and Formability of High-strength Alloy Steel Powder for Selective Laser Melting

目的研究真空感应熔炼气雾化法(VIGA)制备球形24CrNiMoY高强钢粉末并验证其激光3D打印性能。方法阐明不同雾化气压对粉末形貌、流动性等粉体特征的影响,分析选区激光熔化技术快速成形合金钢样品的微观组织和力学性能。结果在9.0 MPa雾化气压下制备的粉末球形度最佳,粉末松装密度达到4.89 g/cm^(3),流动性能为21.4 s/(50 g),粉末含氧量0.023%,空心球率<3%,粉末的微观组织主要是马氏体。经过激光工艺参数调控,SLM成形合金钢试样的激光熔池内存在两个明显不同的微区:激光熔化区(LMZ)和热影响区(HAZ)。LMZ主要是马氏体组织,HAZ主要为下贝氏体组织。合金钢试样的平均显微硬度为(402±5.7)HV0.2,其抗拉强度达到(1246±12)MPa,断后伸长率为(11.6±0.5)%。结论VIGA方法制备的24CrNiMoY高强钢粉末满足SLM技术使用要求,具有良好的激光3D打印成形性。

The work aims to study the preparation of spherical 24CrNiMoY high-strength steel powder by vacuum induction melting gas atomization(VIGA)and to verify its laser 3D printing performance.The effects of different atomization air pressures on powder characteristics such as powder morphology and flowability were elucidated,and the microstructure and mechanical properties of alloy steel samples rapidly formed by selected laser melting were analyzed.The results show that the powder prepared at 9.0 MPa atomization pressure has the best sphericity,bulk density of 4.89 g/cm^(3),fluidity of 21.4 s/(50 g),oxygen content of 0.023%,hollow sphere rate<3%,and the microstructure of the powder is mainly martensite.The laser process parameters were adjusted so that two distinct micro-zones existed in the laser melt pool:the laser melting zone(LMZ)and the heat affected zone(HAZ).The LMZ was mainly martensitic and the HAZ was mainly low bainite.The average microhardness of the alloy steel specimen was(402±5.7)HV0.2,and its tensile strength reached(1246±12)MPa with(11.6±0.5)%elongation after fracture.The 24CrNiMoY high-strength steel powder prepared by the VIGA method meets the requirements for SLM technology and has good formability for laser 3D printing.