Inconel　718　superalloy　has　been　fabricated　by　selective　laser　melting　technology　(SLM).　Its　microstructure　and　mechanical　properties　were　studied　under　solution+aging　(SA)　standard　heat　treatment,　homogenization+solution+aging　(HSA)　standard　heat　treatment　and　as-fabricated　conditions.　Precipitated　phases　and　microstructures　were　examined　using　OM,　SEM,　TEM　and　X-ray　analysis　methods.　The　fine　dendrite　structures　with　an　average　dendrite　arm　spacing　of　approximately　698　nm　accompanying　some　interdendritic　Laves　phases　and　carbide　particles　can　be　observed　in　the　as-fabricated　materials.　After　standard　heat　treatments,　dendrite　microstructures　are　substituted　by　recrystallization　grains,　and　Laves　phases　also　dissolve　into　the　matrix　to　precipitate　strengthening　phases　and　delta　particles.　The　test　values　of　all　specimens　meet　Aerospace　Material　Specification　for　cast　Inconel　718　alloy,　and　the　transgranular　ductile　fracture　mode　exists　for　the　three　conditions.　The　strength　and　hardness　of　heat-treated　SLM　materials　increase　and　are　comparable　with　wrought　Inconel　718　alloy,　whereas　their　ductility　decreases　significantly　compared　with　the　as-fabricated　material.　This　is　because　of　the　precipitation　of　fine　gamma＇　and　gamma　＇＇　strengthening　phases　and　needle-like　delta　phases.　For　the　as-fabricated　alloy,　the　formation　of　finer　dislocated　cellular　structures　that　develop　into　a　ductile　dimple　fracture　shows　excellent　ductility.　Due　to　dislocation　pinning　from　gamma＇　and　gamma　＇＇　strengthening　phases　and　the　impediment　of　dislocation　motion　caused　by　the　needle-like　5　phases,　the　ductility　of　the　SA　materials　decreases　and　causes　a　transgranular　fracture,　compared　with　the　as-fabricated　samples.　(C)　2015　Elsevier　B.V.　All　rights　reserved.