Adhesive Wear
There are three types of wear that occur, often in combination, in barrels, screws, valves and other components. An understanding of nature and causes of adhesive, abrasive and corrosive wear is essential to the selection and use of these components.
This image is an example of adhesive wear – notice how the top of the screw flights have “rolled†over on the edges.
Adhesive Wear
Adhesive wear occurs when two metals rub together with sufficient force to cause the removal of material from the less wear resistant surface. If the two metals have a comparable chemical analysis and hardness, a galling action can occur where one metal is actually welded to the other causing high and low spots where material is added or removed.
The screw and barrel can come into contact with each other during operation. The screw is cantilevered in the barrel and is supported only at its shank and by the plastic in the barrel. When conditions cause excessive contact between the two components, adhesive wear and/or galling will occur on the screw flight OD and the barrel wall.
There are several causes of adhesive wear and galling, all of which can be prevented through the proper design, manufacture and use of the machinery components.