The oil used was vegetable oil and 160N load was applied. The rpm of the disc was 1500 and 2000. In both cases there has been an increase in weight gain after the test?
while with 150N load there is no such weight gain.
It is due to the passive layer formation on the pin. As a result of tribochemical reaction at the contact, a passive layer is formed on the pin, which prevents the further wear of pin. Usually this tribochemical reaction is oxidation of material at the contact in the environmental conditions. You can observe it only at higher load because certain minimum temperature is needed at the contact surface for the tribochemical reaction to take place. Higher the load, higher the temperature at the contact surface and easier the tribochemical reaction. For more on this you can refer to the following article: A Tewari, Wear 289 (2012) (http://bit.ly/1uBOgS0)
thank you so much amin and abhishek.... how can I prove it while presenting the results.
Shubrajit, it would be good if you can do some SEM-EDX analysis of the tip and flat. You should see the oxide phases in the EDX analysis. The phenomenon is quite well known in the tribology community.
It is not uncommon for the stationary pin to weigh more after sliding contact. Why this occurs is explained by third body formation. During sliding, under certain circumstances, a 'tribofilm' can form at the interface. Tribofilm formation could be due to oxidation of the metal surface (probablly not in your case) or polymerization of the lubricant or other possibilities. What happens to this tribofilm?
1) It could be ejected from the wear track, in which case you would find wear debris at the edges of the track (or at both ends of the track in reciprocating slidng contact). This could happen without any wear of the parent surfaces (pin and disk) - hence evidence for third-body formation (i.e., the tribofilm).
2) It could stick to the pin and accummulate a measurable amount of debris on the pin. Think about forming a tribofilm 10 nm thick on a track 250 mm long. If that film detaches from the track and collects on the face of a pin 1 mm across, the thickness of this 'transfer film' would be 2.5 um, i.e., 250 times as thick as the tribofilm on the track. Here, too, all of this can happen without any wear of pin or disk.
Without more details about the size of the pin and geometry of your tribotest setup (which would give contact stress and sliding speed), it is not possible to 'explain' what caused the increase in weight of the pin for the conditions you have specified. But, hopefully you get the picture of third body effects, which go well beyond the simple picture of pins and discs wearing or not wearing.
For more information, search for literature on How Third-Body Processes Affect Friction and Wear.
Shubrait, could you call the materials used in the experiments and the diameter of the pin?
Pin is EN 24 and disc is EN 31. Dia of pin 10mm.
Can I get some Journal paper links...please
Is possible that you have adhesion of the disc material on pin. What the tangential speed?
Dear Mr Bhaumik,
It is possible that wear particles to be trapped in the lubricant layer on the pin.
i DID THE EXPERIMENT WITH LOADS OF 140 and150,160N. I found at 160N there is a weight gain in pin. Can I infer that 160N to be the maximum load the oil can bear... kindly let me know your views
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