Reasons for surface oxidation after mould nitriding

Die nitriding is a chemical heat treatment process in which nitrogen atoms penetrate the surface of the medical treatment mould. If surface oxidation occurs after nitriding the mould, it not only affects the appearance quality of the mould, but also affects the hardness and wear resistance of the mould surface and seriously affects the service life of the mould. Therefore, when we are nitriding the mould, we must understand what factors will cause the surface of the medical treatment mould to oxidize after nitriding, and the corresponding preventive measures.

Reasons for surface oxidation after medical treatment mould nitriding:

1. Leakage of gas nitriding tank or poor sealing of furnace cover.

2. The desiccant in the drying device providing ammonia gas fails, and the ammonia gas passed into the furnace contains moisture.

3. Insufficient oxygen supply when the furnace cools after the nitriding process causes negative pressure in the tank, and the air is sucked to cause oxidation color.

4. After the medical treatment mould is nitrided, the temperature of the furnace is too high to oxidize in the air.

Measures to prevent surface oxidation after mould nitriding:

1. Always check the equipment, replace the leaking muffle tanks in time, and keep the furnace lid well sealed.

2. The desiccant in the ammonia drying device should be replaced regularly.

3. The medical treatment mould after nitriding adopts oil cooling. For the moulds that require strict control of the deformation, a small amount of ammonia gas should continue to be supplied after cooling after nitriding to avoid negative pressure in the furnace. The temperature of the furnace is controlled below 200 ° C to avoid oxidation of the nitriding mould in the air.

4. The nitriding medical treatment mould that has been oxidized can be removed by spraying fine sand under low pressure, and reheated to about 510 ℃ for 4h nitriding. After nitriding, the furnace is cooled to below 200 ℃ and released.