The　ultra-coarse　WC-Co　cemented　carbides　with　additives　of　WB　and　WCoB　have　been　developed.　The　effects　of　WB　and　WCoB　additions　on　the　microstructure　and　mechanical　properties　of　the　prepared　cemented　carbides　were　studied　in　detail.　It　was　found　that　the　additions　have　slight　influence　on　the　mean　grain　size　of　the　cemented　carbides.　The　addition　of　WB　caused　an　inhomogeneous　distribution　of　its　reaction　product　WCoB　in　the　cemented　carbide.　In　contrast,　direct　addition　of　WCoB　avoided　this　problem,　leading　to　its　relatively　homogeneous　distribution　at　the　WC/WC　and　WC/Co　interfaces.　As　a　result,　both　the　hardness　and　transverse　rupture　strength　were　enhanced　in　the　cemented　carbide　with　WCoB　additive.　The　main　reason　for　such　a　behavior　is　that　the　WCoB　phase,　with　intrinsic　high　hardness,　can　form　the　WCoB/WC　and　WCoB/Co　interfaces　with　high　bonding　strength,　which　is　beneficial　to　both　the　toughness　and　fracture　strength　of　the　cemented　carbide.　(C)　2020　Elsevier　B.V.　All　rights　reserved.