The　ultrafine　WC-Co　composite　powder　was　firstly　synthesized　by　in　situ　reactions,　and　was　then　spray-dried　and　heat-treated　to　prepare　the　feedstock　powder　for　the　high　velocity　oxy-fuel　thermal　spraying.　The　effects　of　the　heat-treatment　of　the　spray-dried　powder　on　the　properties　of　the　final　ultrafine-structured　WC-Co　coating　were　studied　in　detail.　The　results　show　that　increasing　the　heating　temperature　leads　to　a　significant　increase　in　the　density　and　the　flowability　of　the　feedstock　powder,　together　with　the　coarsening　of　the　WC　particles.　The　decarburization　during　the　formation　of　the　coating　is　effectively　inhibited.　As　a　result,　the　fracture　toughness　and　abrasive　wear　resistance　of　the　ultrafine-structured　coating　are　enhanced　due　to　the　increased　bonding　strength　of　WC　and　Co　inside　the　splats　and　also　that　between　the　neighboring　splats.　The　present　study　suggests　that　controlling　the　heat-treatment　process　for　the　spray-dried　powder　is　an　effective　approach　to　improve　the　properties　of　the　ultrafine-structured　WC-Co　coatings.　(c)　2012　Elsevier　B.V.　All　rights　reserved.