A Raman spectroscopy investigation into the influence of thermal treatments on the residual stress of polycrystalline diamond

• The thermal residual stress prior to heat treatment is quantified for four different grades of PCD;
• After oil quenching specimens exhibited increases in tensile stress;
• Removal of cobalt from coarse grain microstructures reduces the thermally induced stresses during quenching;
• Cobalt removal is limited for fine grain PCD and little effect on the magnitude of thermally induced stresses was observed;
• The Finite Volume numerical method is used to reproduce and validate experimental results

A systematic study of the residual stress distribution in number of polycrystalline diamond grades was performed using Raman spectroscopy. The analysis focuses on evaluating the stress state in the specimen both before and after oil quench treatment, with a particular emphasis on the role of the second phase material. Prior to heat treatment, measurements along the surface of the specimen indicate an average residual stress in excess of 1.5 GPa for all grades examined. For specimens subjected to oil quenching at 600 °C an increase in the presence of tensile stress was recorded. The removal of the cobalt second phase from the surface of the microstructure had the effect of limiting this increase of tensile stresses on the specimen surface. Numerical modelling of the quench experiment was performed for polycrystalline diamond using the finite volume method (FV). The increase in residual stress, observed experientially after oil quenching was reproduced numerically, validating the experimental approach for approximating the stress distribution on the surface of the specimens.