1. Hardening: It is a process used to increase the surface hardness of a material, typically employed in steels.

2. Annealing: Annealing reduces the hardness of a material, making it more workable. This is particularly important for processing hard materials like cast iron.

3. Normalization: Normalization relieves internal stresses within the material and enhances structural uniformity.

4. Tempering: Tempering is used to control the phases formed during hardening and achieve desired properties.

5. Surface Improvement: Surface improvement processes enhance the surface properties of the material. For example, surface hardening or coating processes fall into this category.

Heat treatment is generally carried out within specific temperature ranges and durations. Different materials have different heat treatment requirements, so the process parameters may vary based on the type of material, intended use, and desired outcomes.