聚晶金刚石复合片（PDC）失效分析与残余应力有限元模拟

发布时间：2018-02-25 06:18

本文关键词： 聚晶金刚石复合片(PDC) 失效分析有限元模拟残余应力结构分析　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚晶金刚石复合片(Polycrystalline diamond compact,简称PDC)由于其极高的耐磨性、硬度与良好的抗冲击性、可焊接性,已广泛应用于油气钻探、矿石开采以及有色金属加工等领域。然而在PDC由高温冷却至室温的过程中,由于金刚石层(Polycrystalline diamond layer,简称PCD层)与硬质合金衬底之间以及金刚石微粉与Co相之间热膨胀系数的差异,某些部位产生残余拉应力,导致PCD层产生微观裂纹,造成产品不合格。故残余应力分布与大小的优化是PDC制备的关键技术之一。本文先以PDC1613为研究对象,对PCD层表面边缘处裂纹的失效原因进行探究。再以PDC1913为研究对象,采用实验与模拟相结合的方法对PCD层表面残余应力的大小与分布进行分析,并对界面结构几何参数对残余应力大小与分布的影响进行探究,提出相关优化方法。实验方面,对采用钴扩散浸渍烧结法(亦称钻扫越式催化再结晶法,简称STCR)制备的PDC样品进行界面形态、组织形貌、成分分布、物相组成以及残余应力表征与测试。结果表明:PCD层与硬质合金衬底界面结合良好;烧结体较为致密,未出现石墨化现象;PDC1613A边缘裂纹处发现Co含量较无裂纹处偏高。数值模拟方面,建立了描述聚晶金刚石复合片冷却过程温度场、应力场的数学物理模型,采用三维"热-力"物理场顺序耦合模拟的方法,经ABAQUS软件模拟了 PDC1913样品的残余应力,实验结果与模拟结果吻合较好,说明模型符合实际情况。并进一步模拟分析了 PCD层厚度H、加强筋倾斜角度Y、加强筋两侧面夹角θ、边缘台阶深度D和宽度W等对PDC残余应力的影响。结果表明:伴随着PCD层厚度H的增加,中心区域的径向压应力减小,边缘区域部分由压应力转换为拉应力,拉应力区域扩大;加强筋倾斜角度Y越小,径向应力的变化越平稳,拉应力区域略微扩大,拉应力峰值几乎没有变化;加强筋两侧面夹角θ对径向应力与环向应力的大小均影响甚微;边缘台阶深度D的增加与边缘台阶宽度W的减小,可以减小边缘最大径向拉应力的数值,缩小拉应力区域。综上所述,通过实验分析和有限元模拟表明:Co含量的局部偏高与边缘径向拉应力结合,导致PCD上表面边缘出现裂纹风险加大。生产单位根据结果分析,适当降低了 Co含量,使产品的合格率有较大提高。
[Abstract]:Polycrystalline diamond compact (PDC) has been widely used in oil and gas drilling because of its high wear resistance, hardness, good impact resistance and weldability. However, in the process of PDC cooling from high temperature to room temperature, due to the difference of thermal expansion coefficient between diamond layer (PCD) and cemented carbide substrate and between diamond powder and Co phase, The residual tensile stress in some parts leads to microcracks in the PCD layer, which results in unqualified products. Therefore, the optimization of residual stress distribution and size is one of the key techniques in the preparation of PDC. Firstly, PDC1613 is taken as the research object in this paper. The failure causes of cracks at the edge of the surface of PCD layer are investigated. The residual stress distribution on the surface of PCD layer is analyzed by the method of combining experiment and simulation with PDC1913 as the research object. The influence of geometric parameters of interface structure on the residual stress distribution and magnitude was investigated, and some optimization methods were put forward. In the experiment, the cobalt diffusion impregnation sintering method (also known as drilling sweep catalytic recrystallization method) was used. The interfacial morphology, microstructure, composition distribution, phase composition and residual stress of the PDC were characterized and measured. The results show that the interface between the PDC layer and the cemented carbide substrate is good, and the sintered body is compact. There is no graphitization phenomenon at the edge crack of PDC1613A and the content of Co is higher than that without crack. In the aspect of numerical simulation, a mathematical and physical model describing the temperature field and stress field in the cooling process of polycrystalline diamond composite sheet is established. The residual stress of PDC1913 sample was simulated by ABAQUS software by using the method of three dimensional "thermal-force" physical field sequential coupling simulation. The experimental results are in good agreement with the simulation results. The results show that the model accords with the actual situation, and the influence of the thickness of PCD layer H, the inclined angle of reinforcing reinforcement, the angle 胃 between the two sides of reinforcement, the depth of edge step D and width W on the residual stress of PDC are further simulated and analyzed. The results show that:. With the increase of the thickness of PCD layer H, The radial compressive stress in the center region decreases, the edge region changes from compressive stress to tensile stress, and the tensile stress region expands. The smaller the angle Y of the reinforcement is, the more stable the change of radial stress is, and the smaller the tensile stress area is. The peak value of tensile stress is almost unchanged, the angle 胃 on both sides of stiffener has little effect on the magnitude of radial stress and circumferential stress, and the depth D of edge step increases and the width of edge step W decreases. The maximum radial tensile stress of the edge can be reduced, and the region of the tensile stress can be reduced. In conclusion, the experimental analysis and finite element simulation show that the partial high of the fraction Co content is combined with the radial tensile stress of the edge. According to the analysis of the results, the content of Co is reduced appropriately, and the qualified rate of the product is greatly improved.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ163

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