Residual stresses in polycrystalline diamond compacts

Abstract

The thermal residual macrostresses in a series of polycrystalline diamond compacts were studied using neutron diffraction. Measurements were made of (1) the average in-plane stress in the polycrystalline diamond table as a function of substrate-to-table thickness ratio; (2) the average in-plane residual stress gradient in both the WC–Co substrate and the diamond table; and, (3) the radial and hoop components of the residual stress in the diamond table as a function of radial position. The average in-plane stress in the diamond table increases in magnitude with increasing substrate-to-table thickness ratio, from −462 to −152 MPa as the ratio goes from 4 to 1. An in-plane residual stress gradient was measured that ranges from about −200 MPa at the free surface to +700 MPa at the substrate/diamond interface in the WC–Co substrate, and from about −600 MPa at the interface to −300 MPa at the free surface in the diamond. The hoop and radial stress components were measured at five points along a radius in the diamond table. The hoop stress was essentially constant (≈−470 MPa) and the radial stress ranged between about −150 and −350 MPa.