Hydrogen Decrepitation (HD) Unit

 HD unit is a special unit used for coarse crushing of the strip cast Nd-Fe-B flakes using Hydrogen gas.   In this process flakes of Nd-Fe-B is encapsulated with hydrogen which diffuses into the alloy and gets adsorbed along the Nd-rich phases in the grain boundaries.    This leads to volume expansion leading to intergranular fracture and results in formation of easily crushable coarse powders