Which process is utilized to enhance the durability and surface finish of metal parts?

The process that enhances both the durability and surface finish of metal parts is shot peening. This technique involves bombarding the surface of the metal with small spherical particles, known as media. This bombardment creates compressive residual stresses on the surface, which significantly improves the material's fatigue resistance and overall durability.

In addition to improving strength, shot peening also contributes to a better surface finish by reducing the surface roughness. The impact of the shot creates a smoothened appearance as it removes imperfections and irregularities on the metal surface. This makes shot peening an effective method not only for enhancing the lifespan of components but also for achieving a desired aesthetic quality.

Other processes like baking, painting, and polishing serve different purposes. Baking typically involves curing materials and doesn’t directly contribute to strength or surface finish improvements in metals. Painting is used primarily for protective and aesthetic coatings rather than altering the physical properties of the metal. Polishing is focused on achieving a high shine and smoothness but does not significantly increase the durability or fatigue resistance like shot peening does. Thus, shot peening stands out as the optimal choice for enhancing both aspects effectively.