Correct option is B
Nitriding is a surface-hardening process in which nitrogen is diffused into the surface of a steel component to improve its hardness and wear resistance. Before the nitriding process, the steel component typically undergoes a heat treatment process. This heat treatment usually involves heating the steel to a specific temperature and holding it for a certain duration to achieve the desired properties, such as stress relief and homogenization of the material's microstructure. The recommended time for this heat treatment process before nitriding is typically within the range of 21 to 100 hours, depending on the specific type of steel and the desired final properties.
