Soft Nitriding Of M2 High Speed Steel And Nitride Brittle Mechanism

Tuff-nitriding of M2 high-speed steel was investigated and improvemented under the following parameters:temperature 560℃,ammonia flow3-8Nm~3/h, Nitrogen flow 6-10Nm~3/h,Carbon dioxide flow0.4-0.6Nm~3/h,two cooling ways:air cooling,oil cooling.Thickness,hardness gradient,microstructure,phase structure,backscattered electron image and residual stress of M2 nitrated steel's nitration case have been analysed by using microhardness instrument,metallographic microscope,X diffraction instrument,electron probing analysis instrument,residual stress measurement instrument;The diffusion Processes of nitrogen atoms and the mechanism of brittleness in the ferritic nitrocarburizing process have been discussed deeply。The results showed that:the vein nitride that lead to the brittleness of M2 high speed steel's nitration case is the main reasons;when M2 high speed steel's nitration cases has White layer and vein nitride,Specimens is very brittle and when M2 high speed steel's nitration cases only has vein nitride,specimen is also very brittle,so this shows that the vein nitride is the main reasons for brittle;Rail carbon compounds of nitrogen of M2 high speed steel's nitration cases in the form of mountain china along the boundary grain boundary Precipitation and distribution is the major cause of brittle,while the formation of mountain china of Carbon and nitrogen compounds hindered nitrogen and carbon continuing to spread and had a cumulative effect,which is the major reason for the vein organization;Reasonable controlling technology parameters are useful to the formation of alloys nitrides which is disperse in nitrocarburized layer after ferritic nitrocarburizing for high-speed steel,thus reducing the brittleness of the nitrocarburized layer,Reduce the rejection rate,yield reached more than 96 percent,Greatly increasing the economic benefits.