Nitriding and related low temperature heat diffusion techniques

- Jun 01, 2018-

This type includes nitriding, ion nitriding, carbon nitriding, oxygen nitriding, sulfur nitriding and sulfur nitriding.These methods treatment process is simple, strong adaptability, core permeability low temperature (480 ~ 600 ℃), small deformation, especially adapt to precision mold surface strengthening, and the nitride layer with high hardness, wearability, good antisticking properties.3 cr2w8v steel die casting mould, after tempering, 520 ~ 540 ℃ after nitriding, less nitride mould service life increase 2 ~ 3 times.America made of H13 steel die casting mould, a lot of nitriding processing, and nitriding in lieu of a tempering, surface hardness up to HRC65 ~ 70, and the lower mold core hardness and toughness, good to get good comprehensive mechanical properties.Nitriding process of die casting mould surface treatment commonly used, but when the nitride layer were thin and crisp white layer, unable to resist the effect of alternating thermal stress, easy to produce micro cracks, reduces the thermal fatigue resistance.Therefore, in the process of nitriding, the process should be strictly controlled to avoid the formation of brittle layer.Recently, secondary and multiple nitriding processes have been proposed in foreign countries.By repeatedly nitriding can be produced in the process of service can be decomposed easily micro cracks of nitrides white layer, increase the nitriding layer thickness, and at the same time make the mould surface residual stress layer is very thick, prolong the life of the mold to improve.In addition, salt-bath carbonitriding and salt-bath sulfur-nitrogen carburizing are also adopted.These processes have been widely used in foreign countries. For example, TFI+ABI process is more widely used in China, which is to soak in alkaline oxidizing salt bath after nitric carburizing in salt bath.The surface of the workpiece is oxidized and black, and its wear resistance, corrosion resistance and heat resistance have been improved.The die - casting die life of aluminium alloy treated by this method is increased by hundreds of hours.For example, the oxynit process developed in France for nitrogenation treatment after sulfur and nitrogen carburization is more characteristic for non-ferrous metal die casting mould.

 


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