Page 321 - Handbook of Materials Failure Analysis
P. 321
318 CHAPTER 13 A concise filtergram wear particle atlas
100µm 100µm
(a) (b)
50µm 50µm
(c) (d)
FIGURE 13.7
The wear particles had been subjected to different degree of the press (200 ): (a) a
fatigue wear particle from a rolling element bearing; (b) a fatigue wear particle from a
compressor; (c) a laminar particle subjected severe press; (d) a laminar particle pressed
from a cutting wear particle.
During the machine’s operation, some wear particles can be further deformed by
the machine component’s rolling and pressing, forming the laminar particles. Hence,
the thickness ratio of laminar particles depends on severity of pressing.
Figure 13.7 displays the wear particles subjected to different degree of press.
Figure 13.7a is a fatigue wear particle from an oil sample taken from a rolling ele-
ment bearing. The particle surface had been flattened. Figure 13.7b is a fatigue wear
particle from an oil sample taken from a compressor. The cracks on the flat surface
indicate severe press. Both particles remained both features of fatigue wear particle
(thicker) and laminar particle (flat surface). Figure 13.7c and d are the wear particles
from an oil sample taken from a rolling element bearing in a Yankee machine. In
Figure 13.7c, the laminar particle had been pressed so severely, forming the big
cracks and the holes. Figure 13.7d is a laminar particle originally from a cutting wear
particle.
Some wear particles lose their magnetic properties although the particles are
generated from the low-alloy steel components. The mechanisms of magnetic
alternation have not been studied. It could be due to the crystal transformation in
the particle formation, such as changing from bcc to fcc, or forming amorphous
structures.