How Surface Treatments Improve Wear Resistance
Surface wear can be a major issue for many components. The surface treatment can have a significant impact on the life of a worn component, and by selecting the most appropriate treatment, extended life can be achieved without the need for redesign.
Increase Hardness to Reduce Abrasive Wear
Hard anodising, for example, increases the surface hardness of an aluminium component and thus reduces abrasive wear. The surface hardness of an electroless nickel plated component is also increased well above that of the base metal to reduce abrasive wear. In addition, hard anodising of aluminium can achieve a surface hardness of 400 to 500 HV for sliding and/or rotating applications.
Add a Low-Friction Layer for Adhesive Wear
The primary form of wear for two sliding metal surfaces is adhesive wear, where small pieces of material are removed from the surfaces in operation. PTFE-composite coatings and similar low-friction surface treatments can help to reduce the amount of wear that such parts suffer, by reducing the surface friction of the two parts in contact. This is particularly useful where parts are in operation without lubrication, or with limited lubrication.
Match Coating Thickness to the Load
A coating which is too thin is of little use in situations where there are high contact loads, whereas a coating that is too thick can crack or delaminate as the substrate flexes. The thickness of a coating should therefore be matched to the expected contact pressure and the number of cyclic loading events that the part is likely to undergo.
Control Surface Texture After Treatment
Surface finish after a surface treatment has to be controlled too. A surface that is too rough will create high contact points, resulting in rapid wear, while a surface that is too smooth will not allow to form a lubrication film. A defined Ra-range will be sufficient to guarantee proper running-in and minimum wear.
Combine a Hard Base with a Lubricious Top Layer
For those applications subject to both abrasive wear and sliding wear, the hardest coating is often combined with a low-friction lubricious surface. This is known as a hybrid coating and often comprises a hard under layer such as an electroless nickel coating, with a PTFE or similar coating applied to the surface. For Surface Treatments, see https://www.poeton.co.uk/surface-treatments/.
Specifying the correct surface treatment to combat specific wear mechanisms is the simplest method to increase the life of engineering components without redesigning them.
