PDC 复合片残余应力优化设计

PDC（Polycrystalline diamond compact，聚晶金刚石复合片）是一种将硬质合金基体与金刚石粉末烧结在一起的复合材料，广泛应用于航天工业，机械加工，地质钻探等领域，成为工业加工，石油天然气开采的“牙齿”。PDC 的制造烧结过程一般采用高温高压制备法，于压机中完成整个工艺过程。由于PDC 原材料金刚石与硬质合金基体存在很大的热胀系数以及烧结中所使用的粘接剂等原因，导致PDC 在降温卸压的过程中会产生较大的残余热应力。这种残余应力的存在会使PDC 因应力过大而产生裂纹，缺陷，甚至发生脱层现象，严重影响了PDC质量，制约了工业生产的发展。本文着重对PDC 残余应力的产生进行研究，探讨影响残余应力的因素，并对这些关键因素进行优化以改善PDC 的应力状态。本文主要对晶锐公司生产的基体型号为R11-1913 的复合片进行残余应力的研究，并对其进行一些改进。一方面通过Rigaku 生产的XRD 衍射仪对其金刚石表面层的残余应力进行测定，研究了表面残余应力的分布规律；另一方面基于有限元法利用ANSYS 的Workbench 模块对PDC 残余应力进行了数值模拟。通过实验数据以及模拟结果的对比，验证残余应力分布的正确性，并在此基础上讨论了影响PDC 残余应力的因素如：厚度比，界面几何形状等，初步得出影响残余应力的最关键因素为金刚石层的厚度以及界面的形状因素。通过控制变量法以数值模拟为基础，研究了外形尺寸不变的条件下R11-1913 的最优设计参数。同样以R11-1913 的外形尺寸为基础，自行设计了异形界面形状的PDC 复合片，并将其与R11-1913 的应力数值模拟结果进行比较，验证设计的优越性。其中新界面PDC 结合面处的平均Mises 应力降低了1/3，并且应力分布更为均匀；剖面最大Mises 应力值降低800MPa；整体PDC 剖面轴向应力比旧界面低100MPa。

Polycrystalline diamond compact (PDC) is a kind of composite material sintered with cemented carbide matrix and diamond powder. It is widely used in aerospace industry, mechanical processing, geological drilling and other fields which is called "teeth" in industrial processing, petroleum and natural gas exploration. PDC's manufacture process generally uses high temperature and high pressure preparation method to complete in the press. Due to the large different coefficient of thermal expansion of PDC material and the reason of the adhesive used in sintering, PDC will generate large residual thermal stress in the process of cooling and pressure relief process. The existence of such residual stress will lead to cracks, defects, and even delamination of PDC, which will seriously affect the quality of PDC and restrict the development of industrial production. This article focuses on the study of residual stress generation of PDC, discusses the factors that affect the residual stress, and optimizes these key factors to improve the stress state of the PDC.This article mainly studies the residual stress of the composite sheet produced by Jinrui with model number R11-1913, and makes some improvements. On one hand, the residual stress of the diamond surface layer was measured by XRD diffractometer manufactured by Rigaku, and the distribution law of residual stress on the surface was studied. On the other hand, the residual stress of PDC was numerically simulated using ANSYS Workbench module based on finite element method. Through the comparison of experimental data and simulation results, the distribution of PDC residual stress is verified. Based on these results, the factors that influence the residual stress of the PDC, such as thickness ratio and interface geometry are discussed. The critical factors are thickness of the diamond layer and the interface shape. Based on numerical simulation, the optimal design parameters of R11-1913 were studied under the condition of constant dimensions. Based on the dimensions of R11-1913, a PDC composite sheet with a profiled interface shape was designed and compared with that of R11-1913 to verify the superiority of the design.The average Mises stress at the interface of the new interface PDC is reduced by 1/3, and the stress distribution is more uniform; the maximum Mises stress is reduced by 800 MPa; the axial stress of the overall PDC is 100 MPa lower than that of the old interface.