A　new　type　heat　treatment　process　comprising　super-high　temperature　pretreatment　and　austempering　treatment　(S&A　treatment)　was　used　to　process　carbidic　austempered　ductile　iron　(CADI).　The　results　showed　that　the　netlike　eutectic　carbides　were　significantly　reduced　after　super-high　temperature　pretreatment.　Due　to　the　increase　in　supercooling　during　super-high　temperature　pretreatment　cooling,　the　inter-laminar　spacing　of　pearlite　was　reduced　from　300　nm　to　100　nm.　When　the　ductile　iron　with　superfine　pearlite　was　reheated,　a　large　amount　of　Fe3C　particles　were　retained　inside　the　prior　austenite　grains.　After　austempering,　a　superfine　ausferrite　matrix　with　a　length　of　1-3　mu　m　and　a　thickness　of　50　nm　was　obtained.　The　main　reason　for　this　refinement　is　the　increased　number　of　nucleation-sites　for　the　austenite　grains　and　the　retardation-effect　of　Cr　on　their　growth.　TEM　results　indicated　that　a　possible　orientation　relationship　between　bainitic　ferrite　with　a　cubic　lattice　and　precipitated　Fe3C　particles　with　a　orthorhombic　lattice　is　(01　(1)　over　bar)(alpha-Fe)//(210)(Fe3C),　and　their　boundaries　are　coherent　boundaries.　The　CADI　obtained　by　S&A　treatment　has　an　impact　toughness　120%　higher　than　the　traditional　CADI　without　sacrificing　hardness,　and　has　excellent　wear　resistance　under　high　wear　load.　(c)　2019　The　Authors.　Published　by　Elsevier　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).