Deformation of parts after plasma nitriding

When the plasma is nitrided, the surface of the part is evenly covered with glow, and the voltage drop is mainly concentrated near the cathode. Under high-energy ion bombardment, the temperature rise rate of the parts is generally uniform. Adjusting the output power of the power supply can control the heating rate and allow the parts to heat up slowly and uniformly. After some temperature homogenization measures are taken, a more uniform nitriding layer can be obtained on the parts. The speed of ion nitriding is fast, and the time of nitriding is short. Therefore, for the bending deformation of long-axis parts, the borehole shrinkage and ellipticity and other deformations of the set of parts, the ion nitriding is smaller than the gas nitriding.

After the plasma nitriding, the size of the part generally increases slightly, but it is less than the gas nitriding. This is because the cathode sputtering counteracts a part of the volume increase effect caused by the infiltration of nitrogen. At the corners of nitrided parts, the result of simultaneous nitriding of two adjacent faces results in a more severe dimensional expansion than the other parts, called edge protrusions. This has an adverse effect on the carrying capacity of the contact surface. Due to the presence of cathode sputtering, such edge protrusions produced by ion nitriding are much smaller than gas nitriding, and sputtering can be enhanced to further reduce the edge protrusions and obtain a more desirable profile.

Lowering the nitriding temperature can significantly reduce the deformation of nitrided parts. Nitriding treatment above 350°C will enhance the effect. The use of low-temperature ion nitriding can often solve the problem of nitriding and deformation of certain parts. At the same time, low-temperature ion nitriding also has the characteristics of keeping the parts high enough in heart strength and enhanced load carrying capacity.