i have a theory...
diamond particles is really hard, and is used as abrasives in industrial applications.
one such example is this being sold on alibaba
http://www.alibaba.com/product-gs/733590813/industrial_diamond_dust.html?s=p
i know this because i have studied machining and machine tool designs as a part of my degree in mechanical engg.
now i do not know about the structure of diamond particles used in this particulat thermal paste.
As far as i know, based on the chemical atomic structure of diamond, the only ways it can exist, is always crystalline, i.e. with sharp edges.
so we are at this point where.. they are basically putting abrasive particles in your thermal compound. i may be wrong, as i have little clue on artificial diamond manufacturing processes, and there might be some special way to get non abrasive diamond particles. (
well, i did a google check and it doesnt produce relevant results)
this would explain the scratches formed on the surfaces.
now to wards the pitting.
i have analyzed the pictures, and most of the cases the pitting seems to have formed on the lower side of the CPU(assuming most people use desktop standing PCs).
my theory is that... after the heatsink has been mounted and set up right, the diamond particles being heavier than the suspension medium, have a tendency to fall under gravity.
this can be tested by applying a small anount of the stuff on an acrylic plate, then putting another one on top, with a small gap between. if my hypothesis is correct the diamond dust will reach the bottom faster and hence tend to be concentrated towards the bottom a bit more.
now the pitting action.
the pitting action is actually a more advanced form of the previous problem.
we all know that the temp cycles go about 30C difference in between noload and loaded conditions.
this produces tiny deformations in the thin IHS of CPUs and in heatsinks. What i mean is, that due to expansion and contraction, the IHS and surfaces will act like a diaphragm and this will sort of provide a pumping action, agitating the particles and further facilitating the previous problem.
now because of any microscopic imperfection in the surface or because of contamination, a small diamond particle might get lodged in a place. now this diamond particle will attract the other atoms on other diamond particles and slowly a large mass will be gathered.
now this will be pressured by repeated movements of the diaphragm action which may result in the pitting action.
also another theory is its just abrasion from movement. like in a sand blaster.
there is already movement from the diaphragm action. maybe it was making distinct same currents everytime? it was eroding like a river
.
Please do post the links here!