A computational study of special grain boundaries in WC–Co cemented carbides

Artikel i vetenskaplig tidskrift, 2015

In this work, we model Sigma = 2 and Sigma = 1 {10 (1) over bar0}parallel to{10 (1) over bar0} WC/WC boundaries in WC-Co using density functional theory (DFT). In particular, the misfit structure of the Sigma = 2 twist boundary is modeled explicitly with a previously developed Peierls-Nabarro model for misfit dislocations. The grain boundary energy of the twist boundary is found to be 0.7 J/m(2), which is small in comparison with energies of general WC/WC boundaries. The misfit structure can be described as a square network of screw dislocations with Burgers vectors 1/6 < 1 (2) over bar 13 >. Our calculations show that Co will not segregate to the Sigma = 2 twist boundary, which contrasts with predictions for other WC/WC boundaries that typically give half a monolayer of segregated Co.