镍基高温合金激光熔覆层摩擦压力剪切变形行为研究

For aiming at the key issues - controlling internal quality and ensuring mechanical properties, to restrict the application of laser cladding technology in remanufacturing repair field, deformation behavior of directional growth columnar dendrite microstructure and mechanism of dynamic recrystallization (DRX) of Non-equilibrium rapid solidification microstructure within the laser cladding layer will be researched in the conditions of Friction hybrid Pressure Shear（FPS） deformation. The changing characteristics on the distribution of pecial low-CSL (coincident site lattice) boundaries wiil be analyzed in the process of the dynamic displacement and the DRX. The deformation process of the laser cladding layer during frictional heating hybrid rotary roll (FHRR) will be simulated by finite element mothed. The mechanical properties of the as-deposited layers and the heat affected zone will be estimated after the FPS deformation. Systemic scientific basis will be provided for controlling internal quality of the laser cladding layer and achieving stable and reliable mechanical properties based on the profound research. Plastic forming foundation of the laser cladding layer will be established. Principle on the FHRR technology and an advanced experimental method-FPS will be put forward so as to establish the control condition of the deformation behavior and the DRX. Grain Boundary Character Distribution (GBCD) will be used for describing complex microstructure characteristics of the cladding layer, and the relationship between the GBCD and the dynamic displacement will be revealled. The experimental method to acquire the plastic parameters and the yield conditions of layered distribution microstructure characteristics will be explored in order to implement finite element simulation on the FHRR deformation of the laser cladding layer. An practical test method to evaluate separately the mechanical properties of the deposited layer and the heat affected zone will be presented. The results of the study will provided with important theoretical significance and application value for establishing a remanufacturing repair theory and developping advanced manufacturing technology.

针对制约激光熔覆技术在再制造修复中应用的关键问题--控制内部质量和保证力学性能，研究摩擦压力剪切变形条件下激光熔覆层中定向生长枝晶组织的变形行为和非平衡快速凝固组织的动态再结晶（DRX）机理，特殊的低重合点晶格晶界分布在动态位移和DRX过程中变化特征；有限元模拟熔覆层摩擦热辅助旋碾变形过程；评价沉积层和热影响区的力学性能。通过系统深入的研究，为控制熔覆层内部质量，获得稳定可靠的优秀力学性能提供系统的科学依据。 提出摩擦热辅助旋碾技术原理和摩擦压力剪切实验方法，建立变形行为和DRX的控制条件；以晶界特征分布表征激光熔覆层复杂组织特征的变形行为，揭示动态位移与晶界特征分布状态之间的关系；探索获取层状分布组织特征的塑性参数和屈服条件的实验方法,给出分别评价沉积层和热影响区力学性能的可行方法。项目成果对建立激光熔覆层塑性变形工艺理论和发展先进的再制造技术具有重要理论意义和应用价值。

控制内部质量和保证力学性能是制约激光熔覆技术在增材制造及再制造中应用的关键，在通过激光熔覆及不同热处理工艺获得具有不同组织特征的IN718试样的基础上，采用多种表征手段研究了熔覆态和热处理态的IN718合金的微观组织、显微偏析、碳化物和析出相特征，利用常温拉伸和纳米压痕试样从宏微观两方面对上述不同组织特征的宏微观弹塑性性能进行比较研究，发展了微观塑性力学参数的纳米压痕结合FEM计算反演分析方法。设计并实施了激光熔覆IN718合金的表面摩擦压力剪切变形试验并建立了表面摩擦剪切变形的FEM模型。对IN718镍基高温合金激光熔覆增材制造组织的系统研究，揭示了其组织的本质特征，表现在微区连续快速凝固控制凝固组织的合金元素分布、基体相形态、析出相的变化具有多重不均匀性；通过对IN718镍基高温合金激光增材制造组织的热处理和塑性变形工艺的研究，全面清晰地描述了热处理和塑性变形对其多重不均匀性组织的影响；对多重不均匀性组织力学性能表征方法的研究，特别是通过对IN718镍基高温合金激光熔覆组织塑性变形行为的分析，深入认识了多重不均匀性组织的力学行为及其塑性变形特点，结合对激光增材制造组织剧烈塑性变形组织的观察和评估，表明熔覆组织形态的塑性变形具有进一步提高金属材料力学性能的潜力，为塑性变形理论发展提供了新的研究领域。