Study On Polycrystalline Diamond Sintering Process Of Stress And The Density Of Finite Element Analysis

Polycrystalline Diamond Compact(abbreviated as PDC)is a kind of super-hard composite material which is sintered from diamond powder and cemented carbide substrate under the conditions of high temperature and high pressure(1350~1500°C,5.5~10GPa).Based on its superior hardness,wear resistance,good impact toughness,weldability,etc.,it is widely used in many fields such as oil drilling,ore mining,and machining of difficult-to-machine materials,which also means for PDC.The performance and quality of the composite sheet put forward higher requirements.This article focuses on the effect of sintering stress of diamond layer on the performance and quality of PDC compact.Based on the modified Drucker-Prager/Cap material model,a material model suitable for pressure sintering is established and the sintering process of diamond powder is simulated.The finite element software Abaqus was used to simulate the diamond powder.The magnitude and distribution rule of the triaxial stress at different levels of the diamond layer were analyzed,which provided the theoretical basis and basis for the influence of the process parameters on the stress distribution of the diamond layer.The density field of the diamond layer was analyzed and studied based on the density parameters related to the density established in the material model.The density distribution of the diamond layer was preliminarily compared with the experimental results in the literature.The influence of top hammer lowering velocity V and height-to-height ratio H/D on the stress and density distribution of diamond layer was analyzed.The variation of stress and density under different parameters was obtained,which provided a theoretical basis for the sintering experiment.Based on the coupled physical field model of "thermal-force",the residual stress of polycrystalline diamond after demolding was studied,and the magnitude and distribution of radial and circumferential residual stress were obtained.Studies have shown that the stress distribution of the diamond layer is not uniform,showing a gradually decreasing trend from the center to the edge,and the third principal stress is obviously greater than the first and second principal stresses;the stress has fromthe upper layer to the intermediate layer between the layers gradually decreasing distribution.Equivalent stress and density gradient become larger with the increase of the down-pressing speed and the ratio of height to diameter;after the mold-released polycrystalline diamond,the radial residual stress is wavy and there is residual tensile stress,and the circumferential residual stress is in the form of a ring.Distribution and are compressive stress.