The invention relates to a nano-crystalline
alloy coating layer and a preparation method thereof. Particularly, the invention relates to a nano-crystalline
alloy coating layer, the components of which, expressed by
atomic ratio, satisfy the relational expression: (Fe1-aM1a)100-x-y-z-Alpha-Beta-GammaCuxSiyBzM2AlphaM3BetaXGamma, wherein, M1 is one or both of Co and Ni, M2 is at least one of Nb, W, Ta, Zr, Hf, Ti and Mo, M3 is at least one of V, Cr, Mn, Al, Sc, Y, Au, Zn, Sn and Re, X is at least one of C, Ge, P, Ga, Sb, In, Be and As, a is more than or equal to 0 and less than or equal to 0.5, x is more than or equal to 0.1 and less than or equal to 3, y is more than or equal to 0 and less than or equal to 30, z is more than or equal to 0 and less than or equal to 25, and furthermore, y plus z is more than or equal to 5 and less than or equal to 30, Alpha is more than or equal to 0.1 and less than or equal to 30, Beta is more than or equal to 0 and less than or equal to 10 and Gamma is more than or equal to 0 and less than or equal to 10, the
volume percent of nano-crystals contained in the nano-crystalline
alloy coating layer is above 50 percent and the
crystal size of the nano-crystals is below 100nm. The invention also relates to the application and a preparation method of the nano-crystalline
alloy coating layer.