重型切削中硬质合金刀具前刀面粘焊变质层损伤机理研究

The bonding breakage of carbide tools in heavy duty cutting is a key problem in large equipment manufacturing. Due to the high temperature and pressure caused by the large amount of cutting in heavy duty cutting, diffusion, melting and recrystallization of affinity elements occurred on tool-chips contact surfaces. The composition and performance of part surface materials on the carbide tool rake face can be easily changed to form stick-bonding metamorphic layers whose material damaging eventually leads to the bonding breakage of tools. Aiming at the material performance and the damaging and failure problems of stick-bonding metamorphic layers on the carbide tool rake face in heavy duty cutting, the project establishes a molecular model of stick-bonding metamorphic layers on tool the rake face in the cutting of typical workpiece materials and obtains the material physical performance parameters; the heat and mechanics distribution characteristics is analyzed on the rake face in cutting process and the separating criterion for stick-bonding metamorphic layers is established; the forming and stripping process of stick-bonding metamorphic layers on rake face is analyzed and the damage variables of stick-bonding metamorphic layers is represented and obtained; the damage threshold conditions of on rake face is determined, and the damage evolution equation and constitutive relations on rake face are established. The numerical simulation of damaging and failure process is given, and the damage evolution discipline of stick-bonding metamorphic layers on rake face is clarified. The research has important theoretical and practical significance to reveal the nature of thermodynamics of bonding breakage of carbide tools and to provide the theoretical basis for the problem of bonding breakage in heavy duty cutting.

重型切削中硬质合金刀具的粘结破损是大型装备制造中的关键问题。由于重型切削超大切削用量引起的高温高压，刀屑界面亲和元素产生扩散、熔融和再结晶，硬质合金刀具前刀面的部分表层材料的成分与性能易发生变化，形成粘焊变质层，粘焊变质层材料的损伤破坏最终导致了刀具的粘结破损。项目针对重型切削中硬质合金刀具前刀面粘焊变质层的材料性能与损伤失效问题，建立典型工件材料切削的刀具前刀面粘焊变质层的分子模型，获得其物理性能参数；分析切削过程中刀具前刀面热力分布特性，建立粘焊变质层分离判据；分析前刀面粘焊变质层的形成与剥离过程，表征并获得粘焊变质层损伤变量；确定前刀面损伤阀值条件，建立前刀面损伤演化方程与本构关系；进行损伤失效过程数值模拟，阐明前刀面粘焊变质层的损伤演化规律。项目研究对于揭示重型切削中硬质合金刀具粘结破损的热力学本质，解决重型切削刀具的粘结破损问题提供理论依据，有重要的理论与实际意义。

重型切削中硬质合金刀具失效是大型装备制造中的关键问题之一。在重型切削超大切削用量引起的高温高压作用下，刀-屑界面亲和元素的扩散运动增强，导致刀具前刀面表层材料的性能发生变化，形成表面变质层，并与切屑产生比较牢固、类似“钎焊”的粘结现象，故而将其称之为“粘焊变质层”。与刀具基体材料相比，刀具前刀面粘焊层的表面硬度、晶体的表面能、晶界内聚力等物理性能均会减弱，致使前刀面损伤演化过程加剧，易产生裂纹，导致刀具的快速磨损或粘结破损，引起较为突出的刀具失效问题。项目通过分析刀-屑粘焊刀具成分，建立刀具前刀面粘焊变质层的分子模型，获得其物理性能参数以及刀屑接触界面结合能；建立了前刀面有无粘焊层两种情况下的传热理论模型和有限元模型，获得了粘焊层的存在及其厚度对硬质合金刀具前刀面温度分布及其梯度变化的影响规律，以及前刀面粘焊层形成到剥离的温度和应力值，初步阐明了前刀面粘焊变质层层形成-剥离过程前刀面热-力特性；分析了刀具失效后的损伤形貌，建立了刀具前刀面扩散磨损理论模型、前刀面裂纹扩展仿真模型以及粘结破损仿真模型，获得了刀具前刀面损伤演化过程中刀具前刀面磨损、破损以及裂纹扩展特性变化规律；分析前刀面粘焊变质层的形成与剥离过程，确定刀具前刀面损伤形式，选择应变能密度和剩余强度作为损伤变量，建立了硬质合金疲劳损伤力学和损伤强度退化模型，进行刀具损伤失效过程数值模拟，实现刀具使用寿命的有效预测。项目相关研究成果，为进一步揭示重型切削中硬质合金刀具的失效机理，提高切削刀具使用寿命，丰富和完善切削刀具设计理论，解决大型装备制造工艺技术难题，有着较重要的理论价值与现实意义。