What purpose does roughness serve in surface finishes?

Roughness in surface finishes plays a significant role in improving strength and wear resistance. A rough surface can contribute to stronger mechanical interlocking between materials, which enhances the overall strength of the bonded components. The variations in height and geometry on rough surfaces can help distribute stress more evenly across a surface, which can also increase its resistance to wear over time. This is particularly important in applications where surfaces are subjected to sliding or abrasive forces.

Surface roughness can also create features that impede the wear process by trapping lubricants or particles, further protecting the material from degradation. Thus, while aesthetic appeal, friction, and adhesion might have their own merits in certain contexts, the enhancement of strength and wear resistance is a primary function of roughness in surface finishes.