Nitrogen-containing martensite composite modified layer with controllable layer thickness on steel surface and process method of nitrogen-containing martensite composite modified layer

The invention discloses a nitrogen-containing martensite composite modified layer with controllable steel surface layer thickness and a process method thereof. The composite modified layer comprises a base body, a nitride layer is arranged on the outer surface of the base body, a nitrogen-containing martensite layer is arranged between the base body and the nitride layer, and an oxide layer is arranged on the outer surface of the nitride layer. A composite structure layer with high mechanical property and high corrosion resistance is designed on the surface of the low-carbon alloy steel, and then the nitrogenous martensite, nitride and surface oxide composite modified layer with controllable layer thickness is obtained from inside to outside by utilizing tufftriding and water vapor oxidation technologies; the nitrogen-containing fine grain martensite supporting layer with the thickness of about 20-30 microns and the gradient nitride layer with the high nitrogen content are combined to provide high hardness an