Based　on　the　specific　structure　of　tubular　solid　oxide　fuel　cell　stacks,　a　good　chemical,　microstructural　and　phase　stability　for　the　protective　coating　are　required　in　both　the　oxidizing　and　reducing　environments.　In　this　work,　MnCo2O4coatings　of　approximately　150　μm　were　deposited　onto　porous　Ni50Cr50-Al2O3substrate　by　atmospheric　plasma　spray　(APS)　process.　The　coated　samples　were　tested　at　800°C　with　the　coating　exposed　in　air　environment　and　the　substrate　in　H2　environment.　Reducing　and　pre-oxidizing　treatments　were　performed　prior　to　the　stability　test.　Then　the　tested　coatings　were　characterized　by　X-ray　diffraction　(XRD)　and　scanning　electron　microscopy　(SEM).　The　XRD　results　elucidated　that　the　tested　coating　had　a　high　structural　stability　on　the　upper　layer,　while　presented　a　reducing　microstructure　on　the　substrate　side.　The　surface　morphology　of　100　hours　tested　coating　indicated　that　the　spinel　granules　still　arranged　closely　with　small　particle　size　of　∼250　nm　and　no　obvious　grain　enlargement　was　observed.　According　to　the　cross-section,　the　upper　layer　kept　stable　and　dense.　While　at　the　underneath　region,　the　microstructure　presented　to　be　rather　porous.　However,　the　resistance　presented　a　decreasing　trend　with　the　extension　of　exposure　duration.　After　exposure　for　95　h,　the　ASR　decreased　to　18.5　mΩ2although　a　substantial　Cr　diffusion　from　the　substrate　was　detected.　©　(2015)　by　ASM　International　All　rights　reserved.