▎ 摘　　要

NOVELTY - An inlet valve comprises base material containing 0.32-0.4 wt.% carbon, 0.17-0.37 wt.% silicon, 2.5-3.5 wt.% molybdenum, 0.5-0.8 wt.% manganese, 0.8-1.1 wt.% chromium, 0.5-1 wt.% tungsten, 0.013 wt.% or less nickel, 0.015 wt.% or less phosphorus, 0.015 wt.% or less sulfur, 0.01 wt.% or less copper and remainder of iron having purity of more than 99.8%. The conical surface of the inlet valve has molybdenum zirconium alloy layer having a thickness of 30-100 microns, and graphene layer. Also claimed is preparation of inlet valve. Also claimed is, preparation of inlet valve. USE - Inlet valve is used for engine. ADVANTAGE - The inlet valve has excellent surface strength, hardness, abrasion resistance and durability. DETAILED DESCRIPTION - An inlet valve comprises base material containing 0.32-0.4 wt.% carbon, 0.17-0.37 wt.% silicon, 2.5-3.5 wt.% molybdenum, 0.5-0.8 wt.% manganese, 0.8-1.1 wt.% chromium, 0.5-1 wt.% tungsten, 0.013 wt.% or less nickel, 0.015 wt.% or less phosphorus, 0.015 wt.% or less sulfur, 0.01 wt.% or less copper and remainder of iron having purity of more than 99.8%. The base material contains impurities including 0.013 wt.% or less nickel, 0.015 wt.% or less phosphorus, 0.015 wt.% or less sulfur and 0.01 wt.% or less copper. The conical surface of the inlet valve has molybdenum zirconium alloy layer having a thickness of 30-100 microns, and graphene layer. Also claimed is, preparation of inlet valve. The inlet valve is prepared by mixing alloy material, melting by a vacuum induction furnace smelting at 1600-1650 degrees C for 2-2.5 hours, forging at 1100 degrees C, 1050 degrees C and 950 degrees C, controlling deformation ratio of obtained product to more than 70%, obtaining inlet valve blank, quenching, heating to 450-500 degrees C, heat-preserving for 2-2.5 hours, cooling by air, removing surface oxide layer, cleaning, subjecting obtained product to ultrasonic surface treatment, nitriding at 330-360 degrees C, welding molybdenum-zirconium alloy containing 30-40 wt.% molybdenum and remainder of zirconium on the resultant product, depositing graphene layer on surface of obtained product by a chemical vapor deposition using methane as carbon source, and hydrogen as carrier gas, at 900-1000 degrees C, and cooling.