基于分区成形激光增材制造一种Fe-Cr-Ni-B钢组织性能研究

Study on Microstructure and Properties of Laser Additive Manufacturing a Fe-Cr-Ni-B Steel by Divided-area Process

摘要:

采用分区成形+整体连接的方式可以有效改善增材制造零件边缘处应力。本文选用一种含B合金钢作为研究对象，对分区成形该合金组织形成机理、成分变化及性能变化进行了研究，验证分区成形该合金的组织、性能相容性。结果表明，该成形方式制备的合金组织由呈条带分布的树枝晶组成，靠近搭接线位置处组织条带出现向生长方向弯曲，整体上而言分区成形不同位置处组织尺寸差异性较小，合金无宏观偏析。合金中组成相由基体相奥氏体相、分布于枝晶间的硼化物+基体相共晶相构成，共晶相形成导致枝晶偏析。性能分析表明，由于硼化物的存在和组织细小，导致合金硬度高、强度高、塑性差，在熔接区域附近显微硬度略低于其他区域，但差异性不大，整体硬度分布较为均匀。

Abstract:

This paper presented a fundamental investigation of the formation mechanism and compatibility of microstructure/mechanical property of Fe-Cr-Ni-B steel samples, these samples were built by the divided-area forming and integral connection methods. The stress at the edge of the specimen produced in additive manufacturing could be reduced by the divided-area forming and integral connection methods. According to the microstructure analysis using stereology microscopy/optical microscopy/scanning electron microscope/X-ray diffractometer/Schaeffler diagram, the macrostructure distributed in strip band geometry and the microstructures consisted of dendrites with the intermetallic phases containing austenite phase, boride/matrix eutectic phase. Additionally, the macrostructure strips near the bonding line bent to the building direction and was discontinuous because of unique forming method. However, the microstructures and compositions of the samples were homogeneous. Due to the existence of boride and the finer microstructures, mechanical properties analysis showed that the alloy had high hardness, high ultimate strength and bad deformability. The hardness distribution was homogeneous apart from some positions of the re-melting zone and the heat-affected zone near the bonding line, which had a limited lower hardness because of difference in microstructure.