脉冲激光(TiC-VC)p/Fe熔覆层组织细化与相关腐蚀行为的机理研究

Laser cladding shows a good application prospect in industry field, however, complete equipment is so expensive, choose cheap iron based alloy powder can make up for the price disadvantage, but the cracking and corrosion resistance of Fe-based laser cladding layer shows still need to be improved. It is found that pulsed wave laser could refine microstructure of in-situ TiC-VC/Fe-based cladding layer, improved its strength and toughness simultaneously, but the refinement mechanism is not clear, and the corrosion behavior and mechanism of refined microstructure is urgently to be further studied. This project intends to combine with the analysis of the heating and cooling process, the laser-induced plasma behavior, the surface and internal flow behavior of molten pool of continuous wave and pulsed wave laser cladding layers, illuminate the refinement mechanism of (TiC-VC)p/Fe cladding layer prepared by pulsed laser, based on comprehensive regulation of pulsed laser, alloy powder particle size and cladding heat input, to complete the exploration of TiC-VC nanocrystallization behavior and effect mechanism, analyse the relevence between corrosion resistance and microstruture size, combine with the analysis of corrosion potential, passivation film density, composition and semiconductor properties, reveal the corrosion resistance behaviour and mechanism. The related research results will provide theoretical basis for microstructure and corrosion resistance improvement of Fe-based cladding layer, and it shows important theoretical significance for preparaing large area and high thickness cladding layers.

激光熔覆技术在工业领域中展现出良好的应用前景，由于成套设备价格不菲，选用廉价的铁基合金粉末可弥补价格劣势，但铁基熔覆层抗裂性与耐蚀性有待提高。脉冲激光可细化原位自生TiC-VC增强Fe基熔覆层组织，提高熔覆层的强度及韧性，然而细化机理尚不明晰，并且熔覆层组织细化后的相关腐蚀行为及机理亟待深入研究。本项目拟结合连续波与脉冲波激光熔覆加热冷却过程、光致等离子体行为、熔池表面状态及熔池内部流动行为分析，阐明脉冲激光细化(TiC-VC)p/Fe熔覆层组织机理；基于脉冲激光与合金粉末粒径及熔覆热输入的综合调控探索TiC-VC纳米化行为及影响机制；解析熔覆层耐蚀性与组织尺寸的关联性，结合熔覆层自腐蚀电位与钝化膜的致密性、组成及半导体特性分析，揭示熔覆层耐蚀性变化机制。相关研究成果将为铁基熔覆层组织与耐蚀性的改善提供理论依据，对制备大面积高厚度激光熔覆层具有重要的理论意义。

本项目以原位自生TiC-VC增强Fe基熔覆层组织细化为切入点，主要研究了脉冲激光熔覆工艺参数、初始合金粉末粒径对熔覆层组织尺寸的影响及其机理，研究了熔覆层耐蚀性随其组织尺寸（熔覆层基体晶粒尺寸与TiC-VC粒径）的相关变化及其原因，开展了原位自生亚微米级TiC-VC纳米化研究。研究发现低频脉冲激光与高频脉冲激光均可细化TiC-VC，低频细化作用更明显，但高频脉冲激光可明显细化熔覆层基体，低频时归因于熔池的快速冷却，而高频时则得益于熔池的高频震荡作用。熔覆层耐蚀性随碳化物粒径减小而提高，随熔覆层基体晶粒细化而降低。随初始合金粉末粒径减小，熔覆层成型变好，熔覆层耐蚀性逐渐升高，原位自生TiC-VC明显细化，TiC-VC的细化主要受控于石墨粒径的细化。采用梯度粒径合金粉末，基于单位体积激光热输入的协同优化，获得原位自生纳米VC增强亚微米Fe基激光超细晶熔覆层，碳化物平均粒径为53nm，约95%的碳化物粒径都低于100nm。熔覆层晶体平均晶粒尺寸为0.90μm，最小晶粒为0.46μm，约70%的晶粒达到亚微米尺度范围，熔覆层耐蚀性约为低碳钢基体耐蚀性的21.60倍。采用水冷氩弧熔覆获得了纳米VC增强超细晶Fe基熔覆层，熔覆层Fe基体平均晶粒尺寸为1.90μm，VC碳化物平均粒径达0.90μm，水冷熔覆层硬度提高375HV0.2, 耐蚀性提高5.6倍。研究成果为Fe基复合熔覆层性能改善提供理论依据，为拓展价廉Fe基熔覆层工程应用提供技术支撑，具有重要的理论意义与实际应用价值。基于上述创新性成果，项目资助发表SCI论文7篇，培养硕士生四名，三名已毕业，一名在读。项目投入经费20万元，支出15.9864万元，各项支出基本与预算相符，剩余经费4.0136万元，计划用于本项目研究的后续支出。