Fatty Liver Gall Bladder

Today I finally managed to go to Milan to do the analysis. Sprockets analyzed are those of the 3rd gear mounted on the clutch and were removed from my bike (TTR600 '99) and the XT's Wish (Forum XT600.it). The wheels show no signs of damage to both contact fatigue (pitting), only that my shot has 26,000 km and the wish of many more (50-80'000).
To isolate a tooth on which to do the analysis I did three cuts: one for the long approximately in the middle of the wheel, and two side (like cake) to remove the tooth. The tooth was then encased in a block of phenolic resin to be able to easily handle. All this can be seen in the first photo. After incorporation, the freshly cut surface of the tooth has been polished by machine with various abrasive papers. Then I attached the sample with a solution of Nital (nitric acid and alcohol) to highlight the hardened layer (you can also see in the picture that is more polished).
At this point I used the micro hardness tester to measure the hardness profiles. The hardness test by pressing a conical tip with a certain force at the surface and studying the imprint left. More material is hard, the smaller footprint, and measuring the latter dates back to hardness. All this happens in a very small scale and is under the microscope: the prints are great for a 20in microns are invisible to the eye. I made a sequence of measures (sewing, in the jargon) from the edge of the tooth (the surface) to about 1 mm in depth, measured every tenth of a millimeter. Plotting the results that jumps out is called the hardness profile.
In the picture there are two aspects to the comparison, let's see what can be said. It is evident that the value of the surface hardness is much greater than that to heart: the material is hardened. This is a classic gears and I expected it to 100%. The value of core hardness is equal in the two-wheel (about 400HV). This tells us that in all probability the material used is the same and is equal also treated in this area (quenching and tempering). Now begins the most critical part in the first value of the cementation of TTR is harder and deeper. This is NOT 'the result I expected: I thought the treatment of TTR was worse than the XT, but it did not appear. But there is a but. The first hardness value is lower than that in TT nell'XT. I do not know explain. It could be a measurement error or it could be the key to the dilemma. The mechanism of damage infatti avviene proprio in quella zona, nei primi 5 centesimi di materiale. Tutto questo ovviamente l'ho scoperto a casa una volta tracciati i diagrammi e quindi non ho potuto fare nessuna prova ulteriore. La prossima volta che vado a Milano rifaccio i profili, misurando con particolare cura nei pressi della superficie. Proverò anche fare delle prove di durezza classiche su quello che resta delle ruote. Se poi è confermata la misura di oggi chiederò aiuto a qualche professorone per cercare di capire com'è possibile che ci sia un profilo di durezza così strano, e magari ci scappa anche qualche analisi al SEM (microscopio elettronico). A presto!