超细硬质合金激光焊接接头“异常晶粒长大”机理及其抑制

项目名称： 超细硬质合金激光焊接接头“异常晶粒长大”机理及其抑制

项目编号： No.51475282

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 机械、仪表工业

项目作者： 徐培全

作者单位： 上海工程技术大学

项目金额： 80万元

中文摘要： 异常晶粒长大是发生在加热过程中的晶粒突然长大现象，特别是在超细硬质合金中碳化钨具有强烈的长大倾向，严重降低机械性能。本项目拟采用理论计算、结合物理实验和数值模拟方法，研究超细硬质合金激光多层焊及焊后退火条件下异常晶粒长大机理及抑制的关键科学问题。重点研究成分和工艺对晶粒异常长大、微观组织、宏观性能的影响规律；明确异常晶粒与粘结相的润湿性机理及扩散、界面迁移及化学反应的基本规律；揭示位错形成及其对焊接接头异常晶粒形核与长大的驱动规律，确定异常晶粒长大的热力学条件及动力学行为。在焊接接头位错、滑移变形与WC/Co(Fe, Ni)界面结构表征基础上，结合基于多场耦合的温度场、应力场数值模拟及实测结果，建立焊态和退火态接头碳化钨异常晶粒长大模型。本项目旨在揭示激光焊焊接接头碳化钨异常晶粒长大机理，提出抑制理论方法，为提高硬质合金与钢的连接能力、推进其在下一代油气运输装备中的应用提供科学基础。

中文关键词： 硬质合金；异种材料连接；激光焊接；晶粒异常长大；塑性变形

英文摘要： Abnormal grain growth (AGG) is an abrupt growth phenomenon at elevated temperature and tungsten carbide (WC) grains have a strong tendency for AGG in ultra-fine cemented carbide. This is devastating for the mechanical properties since these abnormal grains act as initiation points for cracking and breakage. The proposed research focuses on solving critical scientific problems related to AGG mechanism and its inhibition in ultra-fine cemented carbide during multi-layer laser welding and annealing process both experimentally and theoretically (in combine with numerical simulation). The effects of chemical composition and procedure on AGG, microstructure and macro properties are addressed; clarifying the fundamental rules of diffusion, interfacial migration and chemical reaction between abnormal grains and binding phase; revealing the thermodynamics conditions and kinematic behavior of AGG, and dislocation modeling and its influence on nucleation and growth of abnormal grain will be employed to provide the further understanding of driven for AGG. On the basis of characterization of dislocation, slip deformation and WC/Co(Fe, Ni) interface, in combination with experimental results and numerical simulation on temperature field and stress field distribution, this project will model the WC AGG for as-welded and as-annealed cemented carbide welded joint. Research goals include revealing the mechanism of abnormal grain growth in laser-welded ultra-fine cemented carbide and AGG inhibition. The resulting mechanistic understanding of AGG will be used to improve the weldability of cemented carbide during dissimilar welding of cemented carbide and steels, and provide scientific bases for cemented carbide-steel application in next generation oil and gas transportation equipment under conditions of technological importance。

英文关键词： Cemented carbide;Welding of dissimilar materials;Laser welding;Abnormal grain growth (AGG);Plastic deformation