Q1: Nitriding of a steel part does not increase its

ANS:A - grain size.

Nitriding of a steel part does not increase its fatigue limit. Explanation:

1. Grain Size: Nitriding typically does not affect the grain size of the steel. It primarily modifies the surface properties of the steel by introducing nitrogen into the surface layer, forming hard nitride compounds. Grain size is more related to the microstructure of the steel, and nitriding does not significantly alter this microstructure.
2. Fatigue Limit: The fatigue limit, also known as the endurance limit, is the maximum stress level that a material can withstand without fatigue failure after an infinite number of cycles. Nitriding does not directly affect the fatigue limit of a steel part. The fatigue limit is primarily determined by factors such as the material's composition, microstructure, and surface finish, which may not be significantly altered by nitriding.
3. Surface Hardness: Nitriding is known for increasing the surface hardness of steel parts. During the nitriding process, nitrogen diffuses into the surface layer of the steel, forming hard nitride compounds such as iron nitride (Fe3N) and iron nitride (Fe4N). This surface hardening improves the wear resistance and extends the service life of the part in applications subject to abrasion and erosion.
4. Wear Resistance: Nitriding significantly improves the wear resistance of steel parts. The formation of hard nitride compounds on the surface of the part increases its resistance to wear, friction, and surface fatigue. Nitrided parts are commonly used in applications where wear resistance is critical, such as gears, shafts, and cutting tools.

In summary, while nitriding enhances surface hardness and wear resistance of steel parts, it does not directly affect their fatigue limit or grain size. The fatigue limit is primarily influenced by factors other than surface treatment, such as material composition and microstructure.