激光选区熔化成形S136模具钢的显微组织及性能

Microstructure and Properties of S136 Die Steel by Laser Selective Melting

选区激光熔化(SLM)快速成形金属模具,已成为该领域研究和应用的热点。对S136模具钢粉末在较优工艺参数下的SLM成形件进行微观组织及其形成机理研究。分析了测试件与粉末物相组成及受激光功率的影响规律,测定了熔池边界和熔池内部微观性能并分析了存在差异的原因。实验结果表明,SLM成形的S136模具钢试样接近全致密,熔道搭界良好,熔池边界清晰,但仍观察到微孔隙和微裂纹缺陷,在熔池内部和熔池边界及附近微观形貌不同,熔池边界附近呈现柱状晶,熔池内部呈现胞状晶,微观晶粒细小。成形件与粉末物相均由Fe-Cr相和CrFe7C0.45相组成,碳化物相CrFe7C0.45的含量随激光功率的增大而增多,熔池边界的弹性模量和显微硬度比熔池中心低。

Selective laser melting(SLM)for rapid forming metal dies has become a hot spot in research and application in this field.The microstructure and forming mechanism of S136 die steel powder under optimized process parameters for SLM forming are studied.The phase composition of the test piece and the powder and the influence of the laser power are analyzed.The microscopic properties of the molten pool on boundary and inner are measured,and the reasons for the difference are researched.The experimental results show that the S136 die steel specimen formed by SLM is close to full density,the interfaces between molten ways are good,the boundary of molten pools is clear.However,micropore gap and microcrack defects can be observed.The micro morphology is different in the boundary and near the molten pool and in the molten pool.Columnar crystal exists near the boundary of molten pool.Cytosolic crystal lies in the molten pool and the microcrystalline grain is fine.The phases of the formed piece and the powder are composed of Fe-Cr phase and CrFe7C0.45 phase.The content of the carbide phase CrFe7C0.45 increases with the increase of laser power,and the elastic modulus and micro-hardness of the boundary of the molten pool are lower than the center of the molten pool.