Abstract: A dense thick alloy coating with no layered organizational structure and a preparation method thereof are provided. The preparation method includes the following steps: step 1, placing a substrate in a plasma spraying apparatus, controlling a vacuum degree of the plasma spraying apparatus to be 0.2 mbar-0.5 mbar, controlling a length of a plasma flame of the plasma spraying apparatus to be 1000 mm-1200 mm, and controlling a diameter of the plasma flame to be 200 mm-300 mm; step 2, preheating, by using a plasma spray gun, the substrate to a temperature of 700° C.-1000° C. to obtain a preheated substrate; step 3, plasma spraying an alloy powder on the preheated substrate under a specific plasma spraying condition to obtain a sprayed substrate; and step 4, cooling the sprayed substrate after the plasma spraying, to thereby obtain the dense thick alloy coating without layered organizational structure.

Abstract: A bilayer passive film structure of a substrate, comprising an inner layer comprising an oxide of a first element, and an outer layer comprising an oxide of a second element, wherein the passivation potential of the first element is lower than the passivation potential of the second element, and the passivation potential of the second element is lower than the transpassivation potential of the first element. Also a method of forming the above bilayer passive film structure of a substrate, comprising: treating a surface of the substrate containing Cr and Mn. Further a stainless steel comprises, in percentage by weight, 15%<Cr<22%, 13%<Mn<23%, 12%<Ni<23%, and 0.5%<Si<4%, wherein Si can be replaced with an equal amount of Al, Ti or V.

Abstract: The present invention provides a non-magnetic stainless steel with high strength and corrosion resistance and a preparation method thereof. The non-magnetic stainless steel composed of the following components according to percentage by weight: 17%<Cr<23%, 17%<Mn<23%, 17%<Co<23%, 0.5%<Si <3%, and the balance of iron and inevitable impurities thereof. The preparation method includes: (1) melting a raw material and casting it to a mold to obtain a stainless steel block; (2) homogenizing the stainless steel block at 1,100-1,250° C. for 6-12 hours; (3) forging the homogenized stainless steel block at 1,050-1,150° C. with a final forging temperature of 850-950° C. to obtain a plate having a thickness of 5-15 mm; and (4) holding the forged plate at 1,000-1,250° C. for 10-30 minutes and then put it in water for quenching. The non-magnetic stainless steel of the present invention has superior pitting corrosion resistance and mechanical properties.