Wear Factors

The wearing of metal parts is the gradual decay or breakdown of the metal. When a part becomes so deformed that it cannot perform adequately, it must be replaced or rebuilt. Though the end results of wear are similar, the causes of wear are different. It is essential to understand the wear factors involved before making a hard surfacing product selection. It is actually easy to select a surfacing alloy if all metal components are subjected to only one type of wear. However, a metal part is usually worn by combinations of two or more types of wear. This makes an alloy selection considerably more complicated. A hard surfacing alloy can thus be a compromise between each wear factor. The initial focus should centre on the primary wear factor and then the secondary wear factor(s) should be examined. For example: upon examining a worn metal part, it is determined the primary wear factor is abrasion and the secondary wear factor is a light impact. The surfacing alloy chosen should not only have a good abrasion resistance but also a fair amount of impact resistance. There are five major types of wear Abrasive (3 categories)

Impact

Adhesive

High temperature

Corrosive.

Abrasive wear - Abrasive wear is caused due to the foreign materials rubbing against a metal part. 50 - 60% of all wear on industrial metal components is due to this. Abrasive wear is this a wear problem. It can be categorized into three:

a. Low-stress scratching abrasion – This is the least severe type of abrasion where metal parts are worn away through the repeated scouring action of hard, sharp particles moving across a metal surface at varying velocities. The velocity, hardness, edge sharpness, angle of introduction and size of the abrasive particles all combine to affect the amount of abrasion.

b. High-stress grinding abrasion – this is more severe than simple scratching that results when small hard abrasive particles are forced against a metal surface with enough force that the particle is crushed, in a grinding mode. Most often the compressive force is supplied by two metal components with the abrasive sandwiched between the two - sometimes referred to as three-body abrasion. The surface becomes scored and surface cracking can occur.