WC-eta　(i.e.　Co6W6C,　Co3W3C,　etc)　composite　powder　was　synthesized　by　in　situ　reduction　and　carbonization　reactions　using　tungsten　oxide,　cobalt　oxide　and　carbon　black　as　raw　materials.　Mean　particle　size　of　the　as-　synthesized　composite　powder　is　about　155　nm.　Thermal　spraying　powder　with　a　high　density　and　an　excellent　flowability　was　prepared　using　WC-eta　composite　powder　by　agglomeration　and　heat-treatment.　Cemented　carbide　coatings　were　then　fabricated　by　high　velocity　oxy-fuel　(HVOF)　spraying　technique　using　nanostructured　and　commercially　available　low-carbon　WC-12Co　thermal　spraying　powders　as　feedstock.　The　results　show　that　equiaxed　W2C　particles　form　at　certain　amount　in　the　nanostructured　coating　while　cracks　propagate　mainly　along　grain　boundaries　and　phase　interfaces.　However,　the　micron-structured　coating　still　contains　W　besides　W2C,　which　mainly　distribute　in　outer　surface　of　WC　grains.　The　micron-structured　coating　has　stronger　tendency　to　get　transgranular　fracture.　As　a　result,　the　cracks　go　forward　along　a　relatively　straight　path.　Due　to　higher　density,　finer　grain　size　and　much　larger　in-terface　area,　the　nanostructured　coating　has　simultaneously　higher　hardness　and　fracture　toughness　as　compared　to　the　micron-structured　coating.　After　immersion　into　molten　zinc　for　200　h,　the　micron-structured　coating　suffers　from　more　serious　cracking　along　the　directions　perpendicular　and　parallel　to　the　interface　between　coating　and　substrate,　which　causes　the　large-scale　exfoliation　of　coating　material　and　the　corrosion　of　substrate.　In　contrast,　zinc　diffusion　is　not　observed　in　the　nanostructured　coating　and　only　a　few　cracks　perpendicular　to　the　coating/substrate　interface　are　locally　produced.　Moreover,　the　inner　surfaces　of　the　crack　are　covered　with　tungsten　and　cobalt　oxides,　which　inhibit　corrosion　of　the　nanostructured　coating　in　molten　zinc.　Therefore,　the　nanostructured　coating　has　a　promising　corrosion　resistance　against　molten　zinc.