The　effect　of　the　WCoB　addition　on　the　wear　resistance　of　the　ultra-coarse　WC-8Co　cemented　carbides　was　studied　by　experiments　and　finite　element　simulations.　The　results　showed　that　with　the　increase　of　the　WCoB　content,　the　wear　resistance　of　the　ultra-coarse　cemented　carbides　was　greatly　improved.　The　cemented　carbide　containing　1.0　wt.%　WCoB　had　a　friction　coefficient　of　0.281　and　a　wear　rate　of　0.77　x　10-6　mm3/N.m,　which　was　72%　and　46%　of　those　of　the　WC-8Co　counterpart.　The　reason　of　the　significant　reduction　of　the　friction　coefficient　and　wear　rate　was　analyzed.　WCoB　with　high　hardness　distributed　homogeneously　at　WC/WC　and　WC/Co　interfaces,　which　led　to　relatively　homogeneous　distribution　of　the　stress　in　WC　grains　and　supported　the　WC　grains　after　Co　removal.　Consequently,　the　probability　of　brittle　fracture　and　pull-out　of　the　WC　grains　during　wear　process　of　the　cemented　carbides　was　decreased.　(c)　2021　Elsevier　B.V.　All　rights　reserved.