激光原位沉积TiBx/TiC增强钛基复合梯度涂层中颗粒形成机理研究

Using in-situ laser deposition technique to prepare wear-resistant surface layers with integrated gradient, which contents a variety of particle reinforcements with controlled content, size, morphology and distribution, such as in-situ generated TiBx and TiC phases etc.,as well as the matrix of controlled composition and microstructure was proposed in this project to achieve gradient coatings with high reinforcement content, good strength and excellent wear-resistant properties on the surface of titanium alloys...The microstructure evolution and control mechanism of in-situ formatted reinforcements and the matrix metal under different laser processing condition and with different deposition materials will be investigated using the microstructure and property analysis, the measurement and simulation of the temperature field of laser melting pool, the distribution of powder flow and the particle reactions,together with in-situ diffraction of the phase formation analysis. The main effect factors of the amount, size, morphology and distribution of the TiBx/TiC reinforced particles under the rapid solidification of the in-situ laser deposition will be elucidated to obtain a good TiBx/TiC synergistic effect. The wear and oxidation behaviour of the gradient deposited layers will be studied to clarify the influence of the composition and microstructure of the layer on its properties. Establish a primary theoretical model of in-situ laser deposition process，the deposition thickness and microstructure of the coatings and extent its application according to different substrates and surface properties to select coating materials and processes through which could quickly obtain excellent performance coatings.

本项目以在钛合金表面获得高增强相含量、强韧性好、优异耐磨梯度涂层为目标，研究利用激光原位沉积分层制备以原位生成的TiBx 和TiC 多种颗粒增强相可控含量、尺寸、形貌及分布以及基底可控成分及显微组织为综合梯度的表面耐磨层。利用显微组织和性能分析、温度场测量、粉末加热反应生成相的原位衍射分析及计算模拟激光熔池温度场、粉流分布及颗粒反应相结合，研究不同沉积层材料及激光工艺条件下原位生成的增强相及基底显微组织演变等规律及控制机理，深入阐明沉积层中TiBx/TiC增强颗粒在激光原位沉积快速熔凝条件下形成规律及影响颗粒含量、尺寸、形貌及分布主要控制因素，实现TiBx/TiC良好的协同增强效果。研究梯度沉积层成分、微结构对其耐磨及抗氧化性能的影响。初步建立激光原位沉积工艺与沉积层厚度、显微组织等特征理论模型并优化工艺，发展其针对不同基材、不同表面性能需求有效的选定涂层材料及工艺，快速得到性能优良的涂层

钛合金关键部件的表面性能（特别是耐磨性及高温抗氧化性等）是决定其在航空航天、汽车等领域的应用潜力重要因素之一，本项目以如何在钛合金表面获得高增强相含量、强韧性好、优异耐磨性梯度涂层及增强相形成机理为研究目标，按计划有序开展了研究工作，主要针对不同基底黏结相材料（Ti-6-4及TiNi）和添加的B4C及TiB2+C沉积材料体系,系统研究了激光原位沉积工艺参数（激光的输出模式、激光功率密度、扫描速度、搭接率、单沉积层厚等）、粉末添加方法及参数（粉末预置厚度、送粉粉流质量速率、送粉及保护气体的流速）对沉积过程的影响。建立了激光原位沉积熔池温度场分布数学模型，采用COMSOL Multiphysics 有限元软件模拟了激光原位沉积单层涂层激光熔池温度场数值范围为沉积过程的调整提供了参考，获得了沉积过程中优化工艺参数；实测温度场分布情况由于实验条件的限制未获得精确测量，但其温度循环整体趋势与模拟数据相符合，原位反应对温度场的影响及陶瓷相对熔池液流速度场设定条件复杂有待逐步添加可计算假设条件与实验数据进行进一步模拟。表征了优化条件下制备的沉积层包括颗粒及基底成分、形貌、微结构等，分析了其耐磨性能及磨损机制。分析说明了TiB、TiB2 及TiC三种颗粒协同增强的钛基复合涂层特性及其对沉积层性能的影响规律，对各个激光工艺参数及其交互作用因素对获得的沉积层中耐磨TiBx+TiC 增强颗粒的种类、尺寸、形貌及分布的影响规律进行了系统研究。分层以激光原位沉积制备出Ti-6Al-4V或（及）Ti2Ni合金为主要基底粘接相、不同含量、形貌及分布的TiB、TiB2，TiC 协同增强的综合梯度复合涂层, 实现了对梯度涂层中增强相含量控制，具有韧性基底和良好综合耐磨性，为发展激光原位沉积技术针对不同基材、不同表面性能需求有效地选定涂层材料及工艺，快速得到性能优良的涂层提供了参考数据及相关成形规律。