This　paper　presents　a　systematic　study　of　NiCrBSi　and　WC-Co　high　velocity　oxy-fuel　(HVOF)　sprayed　coatings　that　were　deposited　on　substrates　of　various　surface　roughnesses　to　reveal　predominant　bonding　mechanism　under　a　pull-off　test.　During　HVOF　spray,　NiCrBSi　was　completely　melted　while　solid-liquid　two-phase　WC-Co　particles　were　generated　due　to　their　different　thermo-physical　properties.　The　results　showed　that　the　adhesive　strength　of　the　coatings　increases　as　the　substrate　surface　roughness　increases　from　Ra　0.059　mu　m　to　Ra　9.0　gm.　The　mechanism　of　adhesion　of　HVOF　metallic　coatings　deposited　with　the　fully　melted　spray　particles　was　mainly　mechanical　interlocking,　while　the　deposition　with　the　liquid-solid　two-phase　spray　particles　can　lead　to　the　formation　of　the　physical　bonding　effect　in　addition　to　the　mechanical　interlocking.　(c)　2005　Elsevier　B.V.　All　rights　reserved.