激光诱导溶胶凝胶制备TiC复合增强涂层的原位反应机制研究

Featured with the properties of firm metallurgical bonding, low reaction temperature, excellent controllability and low cracking tendency, laser induced sol-gel hybrid technology becomes an effective method to prepare metal matrix ceramic reinforced coating without any flaws. The TiC compound coating was prepared by photochemical reaction using the hybrid technique of laser cladding and sol-gel in this project. The powder plating method was proposed to produce xerogel powder of nanoscale TiO2 coated graphite flake, which can push through the thickness limitation of coating, increase contact area of powder, and then accelerate the chemical reaction. Through the contrast analysis of reaction resultant in thermodynamic equilibrium and non equilibrium state under high density laser radiation, the physicochemical characteristic of C/TiO2 composite powder in remote equilibrium state should be investigated. The relationship of powder composition proportion, laser type, processing parameters, gas atmosphere and reaction resultant should be built up, then the optimum reaction condition of TiC phase, the in-situ reaction mechanism and hybrid hardening theory can be obtained. Finally, the crack-free TiC reinforced coating with hardness of HV1200 and thickness of above 300μm will be gained. This technology can be used on the cutters, molds, drilling tools and valves in extreme friction condition to realize domestic manufacturing for key components.

由于涂层与基体冶金结合、反应温度低、可控性强、可避免高温热作用下的裂纹等特点，激光诱导溶胶凝胶法成为制备无缺陷金属基陶瓷增强涂层的有效途径。本项目利用激光熔覆和溶胶凝胶相结合的方法，在高能密度激光作用下通过光化学反应原位制备高性能TiC增强复合涂层，提出了采用粉末涂覆法制备纳米级TiO2包裹的石墨薄片复合干凝胶粉末，突破涂层厚度限制，增大反应物接触面积，促进反应快速进行；通过热平衡态下反应过程与激光快速加热条件下反应物的对比分析，系统研究强激光作用的远平衡状态下，石墨与TiO2复合粉体的物理、化学反应特性，建立胶体成分配比、激光类型、工艺参数、气体氛围与反应生成物的关系模型，明晰TiC硬质相的反应条件，获得原位反应机理与复合强化可控机制，制备出硬度HV1200、厚度300μm以上、无裂纹的TiC增强涂层，用于极端摩擦工作环境下的切削刀具、模具、钻探工具、阀门，实现高端零部件的国产化制造。

该项目面向工模具领域易磨损零部件的表面性能提升的需求，针对常规陶瓷增强涂层较薄、易于开裂的问题，选用两种代表性材料即45钢和3Cr13不锈钢为研究对象，利用激光熔覆和溶胶凝胶相结合的方法，在高能激光作用下通过光化学反应原位生成TiC复合涂层。选用不同配比的微米石墨、纳米石墨和碳纳米管为碳源，采用粉末涂覆法制备出纳米级TiO2包裹的石墨薄片复合干凝胶粉末，突破涂层厚度限制，增大反应物接触面积，促进反应快速进行。通过热平衡态下反应过程与激光快速加热条件下反应物的对比分析，系统研究了强激光作用的远平衡状态下，碳源与TiO2复合粉体的物理、化学反应特性，建立了胶体成分配比、激光工艺参数与反应生成物的关系模型，明晰了TiC硬质相的反应条件，制备出最高表面硬度达HV1240，最大熔覆层厚度1.5mm，耐磨性能较基体提高达12倍，耐腐蚀性能较基体提高5.5倍的TiC增强涂层。该项目在理论上获得了TiC光化学反应原位生成的机理以及激光复合强化制备TiC增强涂层的强化机制，工艺上获得了无裂纹、大厚度、增强相均匀分布、耐磨性耐腐蚀性能大幅增强的陶瓷复合涂层，用于极端摩擦工作环境下的切削刀具、模具、钻探工具、阀门等零部件的表面性能提升，为高端零部件的国产化制造提供关键技术支撑。