郑步云,陈鑫,雷剑波,王天琪.热处理对激光熔化沉积18Ni300马氏体时效钢微观组织和力学性能的影响[J].表面技术,2023,52(3):388-398.
ZHENG Bu-yun,CHEN Xin,LEI Jian-bo,WANG Tian-qi.Effect of Heat Treatment on Microstructure and Mechanical Properties of 18Ni300 Maraging Steel Prepared by Laser Melting Deposition[J].Surface Technology,2023,52(3):388-398 |
| 热处理对激光熔化沉积18Ni300马氏体时效钢微观组织和力学性能的影响 |
| Effect of Heat Treatment on Microstructure and Mechanical Properties of 18Ni300 Maraging Steel Prepared by Laser Melting Deposition |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.03.037 |
| 中文关键词: 激光熔化沉积 马氏体时效钢 热处理 微观组织 力学性能 |
| 英文关键词:laser melting deposition maraging steel microstructure heat treatment mechanical property |
| 基金项目:国家重点研发计划(2018YFB0407302);国家自然科学基金(61772365);天津市关键技术研发计划(19YFZCGX00870);天津市科技攻关项目(20YDTPJC00780) |
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| 中文摘要: |
| 目的 提高18Ni300马氏体时效钢在工业应用中的力学性能，研究不同热处理对激光熔覆制备18Ni300合金的影响。方法 采用固溶处理(840 ℃/1 h)和固溶处理(840 ℃/1 h)+时效处理(490 ℃/ 6 h)2种热处理方法，利用扫描电子显微镜、X射线衍射仪和拉伸试验机对激光熔化沉积(LMD)制备18Ni300合金的微观组织、力学性能进行研究，根据不同处理方法下的拉伸断口形貌、性能表征及元素偏析行为，分析热处理对力学性能的影响。结果 经固溶处理后，熔池边界消失，在高温保温过程中杂质相与合金元素充分溶解在奥氏体中，冷却后形成了均匀的马氏体组织，与沉积态相比，抗拉强度由662.1 MPa变为611.5 MPa，降低了约7.64%，伸长率由12.328%变为13.832%，提升了约12.20%;经固溶+时效处理后枝晶形貌基本消失，各元素分布均匀，并在基体中弥散分布着Ni3Mo、Ni3Ti型第二相沉淀，抗拉强度达到1 404.6 MPa，提升了约112.14%，伸长率为7.80%，降低了约36.72%，在断口中观察到亚微米级第二相沉淀呈球状或颗粒状，并大量分布于枝晶间。结论 沉积态18Ni300合金主要由马氏体和少量奥氏体组成，致密度良好，拉伸性能表现为强度较低但塑性良好;经固溶处理后，物相均由马氏体组成，元素分布均匀，抗拉强度略微下降，塑性提升;固溶+时效处理对合金起到了弥散强化的作用，抗拉强度大幅提升，塑性显著减弱。在热处理前后试样的断裂机制均属于韧性断裂，第二相弥散强化为热处理后合金力学性能提升的主要原因。 |
| 英文摘要: |
| The maraging steel (18Ni300) is a typical high-strength steel with excellent weldability, good mechanical properties, and strong adaptability to complex working conditions. One of its most obvious advantages is that its heat treatment process is simple and it is less prone to deform after aging treatment. Therefore, the addition of excellent strengthening process will further broaden its application, making it an important material in marine transportation, aerospace, machinery manufacturing and other fields. The work aims to improve the mechanical properties of maraging steel in practical application and study the effects of different heat treatment methods on the preparation of 18Ni300 alloy by laser additive manufacturing. As an additive manufacturing technology with high degree of freedom and high molding efficiency, laser melting deposition was selected as the molding method in this work. Multi-channel multilayer 18Ni300 alloy samples were prepared by coaxial powder feeding. The optimum process parameters were determined after optimization. The heat treatment tests were carried out in a vacuum tube furnace with a heating rate of 3 ℃/min, and the samples were subjected to solution treatment (840 ℃/1 h ) and solution treatment (840 ℃/1 h ) + aging treatment (490 ℃/6 h). The mechanical property was analyzed by INSTRON 5982 material mechanics testing machine. The phase and microstructure were analyzed by D/MAX-2500 X-ray diffractometer (XRD) and ZEISS Sigma 300 scanning electron microscope (SEM) and supporting X-ray diffraction instruction (EDS). The effects of different heat treatment methods on mechanical properties were analyzed through tensile fracture morphology, performance characterization and element segregation behavior under different treatment methods. After solution treatment, the size of dendrites did not change significantly, but the molten pool boundary disappeared. During the high-temperature heat preservation process, the impurity phase and alloying elements were fully dissolved in austenite, and a uniform martensite structure was formed after cooling. The tensile strength changed from 662.1 MPa to 611.5 MPa, with a decrease of 7.64%, and the elongation changed from 12.328% to 13.832%, with an increase of 12.20%. After the solution treatment + aging treatment, the dendrite morphology basically disappeared, the distribution of each element was uniform, and the Ni3Mo and Ni3Ti as second phase particles were dispersed in the matrix. The tensile strength reached 1 404.6 MPa, with an increase of 112.14%, and the elongation was 7.80%, with a decrease of 36.72%. Submicron second phase particles were observed in the fracture, which were spherical or granular and distributed among the dendrites. The as-built 18Ni300 alloy is mainly composed of martensite and a small amount of austenite, with good density and low strength but good plasticity in tensile properties. After solution treatment, the phases are all composed of martensite, the distribution of elements is uniform, the tensile strength is slightly decreased, and the plasticity is improved. The combination of solution treatment + aging treatment has a dispersion strengthening effect on the alloy, so the tensile strength is greatly improved, and the plasticity is significantly weakened. The fracture mechanism of the samples before and after heat treatment belongs to ductile fracture, and the second phase dispersion strengthening is the main reason for the improvement of mechanical properties of the alloy after heat treatment. |
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