Surface three-step nitridation method of aluminium and aluminium alloy

Abstract

The invention relates to a surface three-step nitridation method of aluminium and aluminium alloy, comprising the following steps: 1, removing surface oxide-films; 2, conducting surface nitridation treatment, wherein the step 1 successively comprises: pretreating, conducting a first zinc immersion, washing, removing zinc, conducting a secondary zinc immersion, and washing and drying; and the step 2 successively comprises: discharging oxygen, heating up to let the furnace temperature be 300 DEG C, and controlling the ammonia dissociation rate below 10%; heating up to 560-590 DEG C for the first time; nitriding for the first time at the furnace temperature of 560-590 DEG C; heating up to 620-640 DEG C for the second time; conducting secondary nitriding at the furnace temperature of 620-640 DEG C; cooling to let the furnace temperature be 570-600 DEG C; nitriding for the third times at the furnace temperature of 570-600 DEG C; and denitriding at the furnace temperature of 570-600 DEG C. According to the invention, the surface dense oxide-films of aluminium and aluminium alloy can be effectively removed, the infiltration of nitrogen atoms is benefited, and nitridation treatment can be conducted by using a common gas nitriding furnace, thus the production cost is low, the operation is simple, the adaptability is wide, and the infiltrated layer has good quality.

Description

technical field [0001] The invention relates to a heat treatment process for aluminum alloys, in particular to a two-stage gas nitriding method for the surface of aluminum and aluminum alloys. Background technique [0002] Aluminum and aluminum alloys are widely used in engineering structures and machine manufacturing, especially in the automotive industry, because they have high specific strength and small specific gravity, which can reduce the weight of engineering structures and complete machines without reducing safety and stability. At the same time, aluminum and aluminum alloys also have good machinability. However, with the development of industrial technology, the lower hardness, lower wear resistance and corrosion resistance of aluminum and aluminum alloys make it unable to meet the harsh service conditions such as high relative movement between components, high mass flow and high corrosion. requirements. [0003] At present, the commonly used surface strength...

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Problems solved by technology

[0008] However, this method often requires pre-sputtering before nitriding to eliminate the oxide film

At the same time, the temperature is high, and some even reach 650°C, which causes local melting of the aluminum alloy and because of the high resistance of AlN, in the ordinary DC glow discharge nitriding, with the thickening of the AlN layer, in order to maintain the discharge process, it must be changed Process parameters, thus increasing the difficulty of nitriding, etc.

[0009] In order to obtain a better nitriding effect, many researchers have improved the process and equipment, and successively proposed enhanced plasma ion nitriding, laser-induced plasma nitriding, ECR (electron cyclotron resonance) microwave plasma nitriding, radio frequency (High-frequency) plasma nitriding, etc., but the above-mentioned nitriding processes of aluminum and its aluminum alloys have in common: high equipment requirements and production costs, complicated operation and difficult control, and it is difficult to obtain ideal for large-sized and complex-structured workpieces. uniform nitride layer