WC涂层纳米划痕过程中摩擦学性能及演化特征的分子动力学研究

为研究纳米划擦过程中WC涂层纳米级摩擦演化特征，利用大型原子/分子大规模并行模拟器建立了不同条件（载荷、划痕深度、划痕速度）下的分子动力学模拟模型。结果表明：摩擦力和摩擦系数随着划痕深度的增加而增大；当压头划擦试样时，沿划痕方向在压头前方及凹槽两侧的原子被挤压、剪切、堆积。瞬时摩擦曲线在初始阶段和稳定阶段表现出明显的摩擦学特征，摩擦过程中压头下方区域晶体出现错位、滑移、间隙或空位。随着划痕速度的增加，体系应变能超过原子间相互约束，原子突破约束，在划痕沟槽两侧堆积，堆积的表面形貌和外缘变得粗糙，亚表面晶体结构产生缺陷。本研究有助于在纳米尺度了解WC涂层摩擦过程的微观磨损机理。

Tribological Performance and Evolution Characteristics of WC Coating During Nano-scratching: a Molecular Dynamics Study

In order to investigate the nano-friction evolution characteristics of WC coating during the nano-scratching process, the molecular dynamics simulation model was established under different conditions (load, scratching-depth, scratching-velocity) by the large-scale atomic /molecular massively-parallel simulator. Results show that the friction force and coefficient of friction are increased with increasing the scratching depth. When the indenter scratches the specimen, the atoms are squeezed, sheared, and piled up in front of the indenter and at both sides of the groove along scratching direction. The instantaneous friction curve presents the distinct tribological characteristics during the initial and stable stages, and the dislocation, slip, interstitial, or vacancy occurs in the region under the indenter during the friction process. With increasing the scratching velocity, the strain energy of system exceeds the bonding energy caused by interatomic constraint. The atoms break the constraint and are stacked on both sides of the scratching grooves. Additionally, the surface morphology and the outer edge of accumulated atoms become rough, and defects appear in the subsurface crystal structure. This research provided the microscopic wear mechanism of WC coating at nano-scale during friction process.