Adhesive wear occurs at the interface between two sliding surfaces. A shaft rotating in a bushing is a good example of two such surfaces. If there is insufficient lubrication between the shaft and the bushing, the resulting friction will cause a buildup of heat. This can lead to elevated temperatures at relatively small localized areas, which are high enough to melt the shaft, the bushing, or both. When this occurs, a microscopic weld is momentarily formed between the shaft and the bushing. These “micro welds” are broken within a fraction of a second by the continued rotation of the shaft, tearing a microscopic piece of metal from either or both parts. This process may occur at hundreds or even thousands of locations, with each revolution of the shaft tearing more and more metal from the parts until they fail.