3. Limit wear and damage

Certain coatings limit wear, but their modes of action are often poorly understood and are the subject of ongoing research. The film's effectiveness depends on the substrate (composition, hardness, toughness, etc.). Environmental parameters (humidity, type of gas, etc.) and test conditions (speed, contact pressure, etc.) also play a role. Coating thickness also plays an important role. If it's too thin, it wears out through fatigue. The hardness of the coating also plays a role: a soft coating on a hard substrate is preferred to reduce adhesive wear, and a hard coating to prevent abrasive wear.