激光增材制造300M钢的组织及耐腐蚀性能

Microstructure and Corrosion Resistance of Laser Additive Manufactured 300M Steel

采用同步送粉激光增材制造技术制备了300M超高强度钢试样,并对沉积态和热处理态试样的显微组织和耐腐蚀性能进行了对比分析。结果表明,激光增材制造300M钢的沉积态组织为外延生长的柱状晶,枝晶间距约10μm,连续穿过多个沉积层进行生长,并且相邻的沉积层之间存在层带组织。沉积态试样组织基体主要为马氏体和针状贝氏体。沿沉积方向的贝氏体数量略低于平行于沉积方向。经热处理后,显微组织变均匀,主要为回火马氏体、贝氏体及残余奥氏体的混合组织。激光增材制造300M钢试样不同截面的耐腐蚀性均有所增加。此外,由于300M钢锻件的晶粒尺寸最小,晶界密度相对较高,因此激光增材制造300M钢沉积态和热处理态试样的耐腐蚀性要低于300M钢锻件的。

300 M ultra-high strength steel specimens were prepared by laser additive manufacturing(LAM),and the microstructure and corrosion resistance of as-deposited and heat-treated specimens were analyzed.The results indicate that the microstructure of as-deposited LAM 300 M steel is characterized by the epitaxial columnar dendrites with spacing of 10μm,which grows continuously through multiple deposited layers,and there exists band zone between adjacent layers.Microstructure of the as-deposited specimens is composed of martensite and acicular bainite,where the amount of bainite along the deposition direction is slightly lower than that parallel to the deposition direction.After heat treatment,the microstructure becomes uniform,which is mainly a mixture of tempered martensite,bainite and retained austenite,and the corrosion resistance of different sections of LAM 300 M steel specimens is increased slightly.In addition,300 M steel forgings exhibit the minimum grain size and relatively high grain boundary density.Therefore,the corrosion resistance of as-deposited and heat-treated specimens of laser additive manufactured 300 M steel is lower than that of 300 M steel forgings.