Guide to Abrasive Wear

On this page you can learn about abrasive wear and how to reduce it.

Definition of Abrasive Wear

Abrasion is the most common form of wear in industry. It is defined as:

'The action of a hard, sharp material cutting through the surface of a softer material'

The abrasive may be products like coal, cement, rock, glass, ceramics or ore. It may be being processed; that is mined, crushed, extruded or conveyed. The consequent wear of machinery and parts is called:

'High Stress, Two-Body Abrasion'

and requires hard, tough and thick surface coatings to combat it.

The abrasive may be present as a contaminant in a product, for instance sand in oil being pumped ashore. Facilities like pumps and valves will have abrasive trapped between rubbing surfaces (for instance bearings), with crushing of the particles to cause sharp abrasive edges. This is called:

'Three-Body Abrasion'

and, since high stresses are involved, requires hard, tough surfaces.

Finally, the abrasive may be present within the product, either as a filler or a pigment. For instance, glass fibres in plastics, pigments like titania in textiles or chrome oxide in ink (printing, paper handling), cellulose in wood or grain, abrasive elements in medical, tobacco or food products, etc. Components handling such products suffer what

'Low Stress Abrasive Wear'

and can usually be combated with hard, relatively thin coatings.

Typical High Stress Abrasive Wear Rankings

Abrasive wear tests can provide only RELATIVE performance rankings. The actual wear rate that might be found in a practical application will depend on many factors, not least load, particle hardness, particle density, particle shape and size, as well as temperature and the environment.

In the case of High Stress Abrasive Wear, the hardness of the coating or surface being abraded is not always the crucial factor; the thickness (or case-depth) of the layer, its toughness and load carrying capacity, and the support provided by the substrate are all important factors.

 

Typical Low Stress Abrasive Wear Rankings

Abrasive wear tests can provide only RELATIVE performance rankings. The actual wear rate that might be found in a practical application will depend on many factors, not least load, particle hardness, particle density, particle shape and size, as well as temperature and the environment.

In the case of Low Stress Abrasive Wear, the hardness of the coating or surface being abraded is often the crucial factor, so that when the loads are light even very thin coatings can provide wear protection.

 

Coatings to Reduce Abrasive Wear

Low stress abrasion can be combated by relatively thin, hard coatings, The criterion for selection is that the coating hardness should be at least 20% higher than the hardness of the abrasive that is causing the problem. You should consult the coating supplier for guidance in this area. Some options are:

• Apticote 100 Hard Chrome plating
• Apticote 300 Hard Anodising of aluminium alloys
• Apticote 400 Electroless Nickel coatings
• Apticote 800 Thermally Sprayed ceramics and cermets
• Apticote Keronite 3000 on aluminium alloys

High stress abrasion cannot be solved by simply increasing the surface hardness. The coating must be tough and be able to withstand large crushing forces. It must be self-supportive and be backed by a resilient substrate. The best coatings are:

• Apticote 100 Hard Chrome plating
• Apticote 800 Thermally Sprayed ceramics and cermets