Evaluation method for the mechanical diamond retention of impregnated bit matrix

Abstract

The diamond retention of traditional impregnated diamond matrix comes from the mechanical holding force. The residual compressive stress on the diamond surface is an important index used to evaluate the mechanical holding force. The existing calculation methods for the compressive stress were compared and evaluated. The results showed that the calculation results of the empirical formula and the representation formula of the elastic equation were quite different from the actual value, revealing that the forms of the formulas were not reasonable enough. The mechanic calculation formula based on the theory of elastic-plastic mechanics, and the finite element numerical simulation method had very good validity. The analysis of the cooling process of WC-based diamond composites after sintering showed that there occurred plastic deformation inside the matrix during the cooling process, and that around the diamond particles there formed a plastic deformation zone. The plastic deformation could absorb a part of the strain energy, relieve the thermal mismatch stress between the diamond and the matrix, and release part of the static pressure stress on the diamond surface. After cooling, the residual compressive stress would occur on the diamond surface and was the source of the mechanical holding force of the matrix to diamonds.

Keywords

• diamond surface pressure
• elastoplastic model
• radius of plastic zone
• analytic calculation