How much ammonia decomposition rate should be controlled during nitriding
Sep. 30, 2020
How much ammonia decomposition rate should be controlled during nitriding
In the nitriding process, steel parts are the catalysts for the decomposition of NH3. Only NH3 in contact with the surface of the workpiece can provide active nitrogen atoms. Therefore, the lower the ammonia decomposition rate, the more ammonia will come into contact with the workpiece, and the stronger the ability to provide infiltrated nitrogen atoms to the workpiece. However, the decomposition rate should not be too low, otherwise it is easy to cause a brittle white layer on the surface of the alloy steel workpiece. The low ammonia decomposition rate also reduces the hardness of the nitrided layer. Therefore, the ammonia decomposition rate is generally controlled between 15% and 40%.
The ammonia decomposition rate is adjusted by the ammonia flow rate. When the ammonia flow rate is constant, the higher the temperature, the greater the decomposition rate. In order to make the ammonia decomposition rate reach the value specified by the process, the ammonia flow must be increased.
