Ni-based　alloy　powders　with　different　contents　of　cobalt　(Co)　have　been　deposited　on　a　42CrMo　steel　substrate　surface　using　a　fiber　laser.　The　effects　of　Co　content　on　the　microstructure,　composition,　hardness,　and　wear　properties　of　the　claddings　were　studied　by　scanning　electron　microscopy　(SEM),　an　electron　probe　microanalyzer　(EPMA),　X-ray　diffraction　(XRD),　a　hardness　tester,　and　a　wear　tester.　The　results　show　that　the　phases　in　the　cladding　layers　are　mainly　,　M-7(C,　B)(3),　M-23(C,　B)(6),　and　M2B.　With　the　increase　in　Co　content,　the　amounts　of　M-7(C,　B)(3),　M-23(C,　B)(6),　and　M2B　gradually　decrease,　and　the　width　of　the　eutectic　structure　in　the　cladding　layer　also　gradually　decreases.　The　microhardness　decreases　but　the　wear　resistance　of　the　cladding　layer　gradually　improves　with　the　increase　of　Co　content.　The　wear　resistance　of　the　NiCo30　cladding　layer　is　3.6　times　that　of　the　NiCo00　cladding　layer.　With　the　increase　of　Co　content,　the　wear　mechanism　of　the　cladding　layer　is　changed　from　abrasive　wear　to　adhesive　wear.