Page 338 - Handbook of Materials Failure Analysis

11 Babbitt Alloy Wear Particles 335

100µm 50µm
(a) (b)
FIGURE 13.35
The copper alloy wear particles (200 ): (a) a copper alloy fatigue wear particle from a
gearbox; (b) a copper alloy sliding wear particle from a geothermal steam turbine.

Figure 13.39 shows the typical severe wear particles in this scenario. The parti-
cles were from an oil sample taken from the gearbox drain. The copper alloy sliding
wear particle (Figure 13.39a) could be from the bearing cage. Other large-size wear
particles (Figure 13.39b–d) signify the onset of severe wear.

11 BABBITT ALLOY WEAR PARTICLES
Babbitt alloys (commonly known as “white metal” in the industry) are widely
applied in the slide bearing pads due to its low coefficient of friction, high fatigue
strength, and excellent seizure resistance. Babbitt alloys are tin-base alloys with
Sn-Sb-Cu and Sn-Sb-Pb systems commonly applied to bearing pads.
Unlike steel wear particles, large-size babbtitt alloy wear particles are rarely
caught in the oil samples. But they can be caught from the oil drain or found on
the oil filters. Figure 13.40 shows the large-size babbitt alloy wear particles from
the oil drain of a hydro-turbine. The particle in Figure 13.40a retains the “white
metal” appearance. However, the tin-base alloys are sensitive to oxidation. Babbitt
alloy wear particles usually appear with colorful oxide film on the particle surface
(Figure 13.41b). Figure 13.41 shows the babbitt alloy wear particles with different
color films.
After oxidation, some color babbitt alloy wear particles would be misinterpreted
as other types of particles. For example, Figure 13.42a looks like a copper alloy wear
particle, whereas Figure 13.42b resembles a steel wear particle. However, both par-
ticles were from the hydro-turbine. ESEM/EDS analyses results (Figures 13.43 and
13.44) of the particles further confirm that both the two particles were from the
Sn-Sb-Cu babbitt alloys.