Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
water lubrication is given in Figure 11. Ni-P nanocomposites have attracted scientific and industrial interest because of their mechanical and chemical characteristics and they are considered a potential replacement for hard chrome coatings. From this figure it can be seen that water lubrication under some conditions can be as efficient as a conventional grease lubrication, while being environmental friendly. The friction in a sliding system, when measured in water, shows the lowest and most stable evolution, compared to unlubricated conditions and even to grease lubricated conditions.
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Figure 12. effect of water on (a) friction and (b) wear industrial materials and coatings.
In Figure 12(b), materials above the line have a lower wear in water, but below the line have an increase in wear. This behaviour strongly depends on the ability of the material to form protective layers and on the influence of the friction mechanism on those layers.
Figure 11. effect of different environments on the frictional behavior of Ni-P nanocomposites against corundum.
Naturally, it is equally important to compare the wear damage synergy by water as an environment. In many cases water lubrication can significantly decrease the friction of a tribosystem when compared to dry conditions, but that does not mean that it would have the same influence on the wear resistance. A typical example is given in Figure 12, where the influence of water lubrication on the friction and wear is mapped for various industrial materials and coatings. Figure 12(a) shows that the friction reduces when going from dry to water lubricated conditions (above the line) but in terms or wear damage, the picture is a bit more varied.
Conclusion Tribocorrosion is an important issue in industry, examples can be found in many fields and diverse applications. Equipment can be easily adapted to testing in such conditions, but the real advantage of tribocorrosion testing lies in developing meaningful test protocols and building an understanding of the synergies at play. The latter requires a lot of experience in two fields of testing. On the one hand, tribological test development: how can we build a test protocol that correlates with reality. And on the other hand, electrochemical know-how is required: how can we interpret the electrochemical measurements and use them to our advantage?
LINK
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LUBE MAGAZINE NO.136 DECEMBER 2016
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