Fretting corrosion adhesion

Mechanism. Basically, fretting is a form of adhesive or abrasive wear, where the normal load causes adhesion between asperities and oscillatory movement causes ruptures, resulting in wear debris. Most commonly, fretting is combined with corrosion, in which case the wear mode is known as fretting corrosion. For example, in the case of steel particles, the freshly worn nascent surfaces oxidize (corrode) to FejO, and the... 

There are other mechanisms such as fretting, fretting corrosion, and fretting CF, which is a combination of adhesive, corrosive, and abrasive forms of wear. Wear by all mechanisms except fatigue mechanism, occurs by gradual removal of material. One or more of these mechanisms may be operating in a particular machine. In many cases, wear may be initiated by one mechanism but may proceed by other mechanisms and thereby complicate failure analysis (60). 

For systems consisting of common materials (e.g., metals, polymers, ceramics), there are at least four main mechanisms by which wear and surface damage can occur between solids in relative motion (1) abrasive wear, (2) adhesive wear, (3) fatigue wear, and (4) chemical or corrosive wear. A fifth, fretting wear and fretting corrosion, combines elements of more than one mechanism. For complex biological materials such as articular cartilage, most likely other mechanisms are involved. 

Anaerobic adhesives of appropriate viscosity are often used to augment and standardise the performance of shrink and interference-fitted components, where they can reduce hoop stress in the outer component and reduce its tendency to crack or display fretting corrosion. These benefits stem from the ability of anaerobics to fill the voids that are present in even the best-prepared surfaces. This spreads loads evenly over the whole of the faying surfaces instead of concentrating them on the engaged peaks, which represent only a small proportion of the theoretical contact area. 

One major benefit of bonded joints is their superior fatigue resistance compared with mechanically fixed assemblies. The dynamic performance of anaerobic adhesives has been assessed. It has been proposed that, since the adhesive makes intimate contact with the metal surface, it fills all the micro-roughness in the surface, so ensuring that the bond line is completely filled. This means that loads, particularly compressive loads, are more evenly distributed over the joint area in comparison with mechanically assembled parts, especially when these are interference fitted. In the latter case there is rarely more than 20% of the available bond area actually in contact. In addition, the ingress of air is suppressed and fretting corrosion is eliminated. The net result is a superior performance under demanding dynamic conditions. 

Again, wear is the removal of material. The idea that friction causes wear and therefore, low friction means low wear, is a common mistake. Brief descriptions of five types of wear abrasive, adhesive, fatigue, chemical or corrosive, and fretting — may be found in Reference 2 as well as in other references in this article. Next, it maybe useful to consider some of the major concepts of lubrication. 

Sn 8-12 Soft and ductile low melting Overlay coatings for pistons point resistant to fretting, in internal combustion scuffing and adhesive wear engines corrosion protection ... 

---