Stop fretting corrosion and false brinelling

Bearings stand out among the components most used on machines of any typology and complexity, due to their capability of decreasing the friction between two objects in mutual movement. Friction that is significantly lower in rolling bearings than in sliding ones, due to their intrinsic design. In their turn, rolling bearings, depending on the application type they are intended for, can be subdivided into ball, roller or gear bearings, called to satisfy some determinate structural and performance characteristics according to the function they must perform, in the system where they are integrated. Concerning this, let us think for instance of the common bicycles and their headset, that is to say the mobile connection between the front wheel and the rear part: their function is fundamental for both the drive experience and for safety. Even small movements of the handlebar can in fact change the direction of the moving vehicle. In most bicycles, ball bearings are used, that is to say a quite cheap typology, easily assembled and with low friction. In some cases, especially for high-end bicycles, the more precious cylindrical roller thrust bearings are used, characterized by more resistance to false brinelling. In both cases, a good lubrication is needed, also to avoid significant impacts on wear and maintenance intervals.

In this context, among the protagonists of the lubricant market and part of  Coventya Group, Microgleit can satisfy any requirement to solve problems connected also to fretting corrosion and false brinelling, as it develops and produces a broad range of tribological specialties distributed by Tools Distribution.

Utmost performances, minimum wear

If we look at the steering head bearing when riding any moving bicycle, we will notice just very small movements in radial directions (just few degrees). The higher the speed will be the more limited movements will be, as easily imaginable. In axial direction, the bearing is expected “to bear” all loads, that is to say the weight of the bicycle and of the cyclist. Therefore, all dynamic impacts are transferred from the front wheel/fork, including eventual shocks and vibrations. The combination of small oscillatory movements and specific high loads make bearings vulnerable to fretting corrosion and to false brinelling, with easily imaginable consequences.

The solution to avoid them consists in turning to frequent maintenance with the eventual replacement of bearings, or we can use a suitable lubricant.

In this context, GSV 791 lubricant by Microgleit, part of Coventya Group, whose products are distributed by Tools Distribution, is ideal wherever there are fretting corrosion problems. Therefore, not only to solve criticalities in the roller bearings equipping the headset of any bicycle, but for instance also in applications with sliding guides, ball joints and power transmissions. We are in fact speaking of a high-performance state-of-the-art white lubricant, made of a special soap with lithium complex, synthetic oil and a combination of solid synergistic lubricants, microWhite.

Confirmed suitability

To establish the applicative suitability of GSV 791 lubricant by Microgleit, some “SNR FEB2” tests were carried out, whose configuration approaches the tribological environment of steering bearings. In this test, they have applied on two ball bearings some small oscillatory movements under high axial loads, in other words under difficult operation conditions. Test results clearly highlight how the bearings lubricated by Microgleit GSV 719 are not affected by wear. Contact areas show very thin tribo-chemical reaction layers, which protect the bearing against wear and improve the regular operation.

The chart shows the results of the “SNR FEB2” test, that is to say the comparison among wear volumes of bearings lubricated with Microgleit GSV 719, compared with “traditional greases”

The “reference grease” used is a high-quality grade with white solid lubricants, used for instance in the bearings of wind power plants to avoid the false brinelling and other damages through vibrations or oscillations. Microgleit GSV 791 lubricant has overcome the benchmark under all respects. After the distance test, the wear volume detected was by far inferior. The grease consistency as well was still good, whereas the benchmark was completely worn out, fractured. It showed deep wear signs, including red salt particles caused by fretting corrosion.

 

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