Measurement of residual thermal stress in WC–Co by neutron diffraction

Stress measurements in ZrB2–SiC composites using Raman spectroscopy and neutron diffraction

“…While neutron diffraction has been extensively used to measure the internal stresses of composite materials, [38][39][40][41] it has also been shown that the measured lattice parameter shifts expected due to CTE mismatch can be altered by changes in chemistry. 42 If the third phase had the same effect on the SiC as on the ZrB 2 , that of increasing the lattice parameter, it would mask some of the contraction in lattice parameter due to compressive stress and could result in a lower measured stress. In light of this, further neutron diffraction experiments could benefit from production of samples without any WC impurity to confirm the SiC lattice parameter data and collect complementary data for lattice parameter changes and residual stresses in ZrB 2 .…”

Residual Stresses

“…Thus, creep or other time-dependent changes with temperature (e.g. phase change, precipitation, and composition) are problematic with respect to the direct measurement of change in the binder phase (Mari, Clausen, Bourke, & Buss, 2009). …”

“…Mari et al measured stress as a function of temperature in WC-11 wt% (17.8 vol%) Co, and followed two heating-cooling cycles from room temperature to 1273 K (Mari et al, 2009;Mari, Krawitz, Richardson, & Benoit, 1996). Above about 1000 K, the cell parameter of Co increases due to solubility of W and C, not to residual stress.…”

Carbon distribution in WC based cemented carbides

“…On one hand, releasing the carbon from the binder phase reduces the lattice strain of cobalt and also reduces the residual tensile thermal stress in the binder phase caused by the difference of the thermoexpansion rates between WC and Co [40,[70][71][72][73][74][75][76]. On the other hand, the formation of the free carbon phase at the carbide-binder interface puts a mechanical compression stress back onto the cobalt binder.…”