from 28 June 2015 to 3 July 2015 (Africa/Johannesburg)
SAIP2015 Proceeding published on 17 July 2016
X-ray diffraction and Raman spectroscopy based residual stress measurements for assessment of fatigue in leached polycrystalline diamond tool bits
Presented by Mr. Maxwell VHARETA on 30 Jun 2015 from 15:20 to 15:40
Type: Oral Presentation
Track: Track F - Applied Physics
Polycrystalline diamond (PCD) cylindrical tool-bits are complex materials systems. One aspect that has a significant influence on the in¬–service behaviour and lifetime is the residual macro-stress state created as a result of the difference in coefficients of thermal expansion (CTE) between the diamond table and the WC-Co substrate. Leached PCD, where the near-surface cobalt has been removed from the PCD layer, has a longer in-service lifetime and the reasons for this are not well understood. The measurement and study of the average in-plane stress fields on the surface of the PCD thus becomes crucial in understanding the in–service behaviour with the quest to have an extended life for the tool-bits. Two complementary non-destructive techniques namely Raman spectroscopy and X-ray diffraction have been employed for residual stress measurements on detached PCD layer samples of 16 mm in diameter and 2 mm in thickness. The Raman peak reveals both the nature and magnitude of the stress present in the material but it is essentially a surface technique with the depth penetration of the visible light being limited by the transparency of the PCD to only a few microns. The X-ray Diffraction technique probes the change in the spacing of the atomic planes of the diamond crystals with strain and has a larger penetration depth. Employing the ball on three balls fatigue set-up the samples were cyclically loaded under constant amplitude load control at a frequency of 10 Hz at room temperature and pressure conditions. Raman and XRD residual stress measurement were done as a function of the number of fatigue cycles to study the surface and near-surface stress under increasingly severe fatigue conditions. These are compared with published Raman spectroscopy results on unleached PCD.
Dr Rudolph Erasmus Rudolph.Erasmus@wits.ac.za School of Physics University of the Witwatersrand