The　chromia　layer,　which　is　formed　during　the　pre-oxidation　process,　can　suffer　from　the　reduction　during　the　carburizing.　However,　the　oxide　coating　retards　the　growth　rate　of　the　external　carbide,　and　thus　permits　the　development　of　the　inner　silica　layer.　Nevertheless,　wedging　crack　of　the　silica　layer　during　cyclic　carburizing　facilitates　the　internal　carburization.　For　the　comparison,　the　high　grain　boundary　density　within　the　Ni,　Al　rich　layer　of　aluminium　adopted　alloy　promotes　the　severe　internal　carburization.　However,　as　the　ion　diffusion　has　been　blocked　by　the　integrity　outer　alumina　layer,　the　pre-oxidized　Al-adopted　alloy　almost　unaffected　during　cyclic　carburizing.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.