Page 438 - Failure Analysis Case Studies II

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Table 2. Smeared material on the outer race
Region I Region I1 Region 111
Fe 35.3 27.0 24.6 36.0 80.7 75.8 92.6 96.3
Cu 56.6 63.7 65.1 55.4 14.6 18.5 4.4 1 .o
AI 4.6 5.6 5.5 4.9 1.2 1.8 0.2 0.4
Mn 1.0 1.1 1.2 1 .O 0.5 0.8 0.3 0.4
Cr 0.7 0.4 0.2 0.3 1.6 1 .o 1.7 1.8
Ag 1.5 2.0 3.3 2.1 1.2 1.7 0.3 ~
Si 0.4 0.2 0.2 0.3 0.3 0.4 0.4 0.2

Table 3. Smeared material on the inner race
Region I Region I1 Region I11 Region IV
Fe 92.3 92.2 97.0 96.9 90.0 83.8 77.7 71.3 72.0 97.5 97.0 81.8 84.9
Cr 6.6 7.2 1.0 0.9 1.7 1.3 5.0 5.7 5.8 1.6 1.9 1.6 1.7
Mn 0.4 0.2 1.2 1.2 0.2 0.5 0.7 0.8 0.7 0.4 0.4 0.5 0.5
Si 0.8 0.5 0.9 1.0 0.3 0.4 9.6 11.8 10.9 0.3 0.3 0.1 0.3
cu - - - - 6.5 11.3 - 0.3 0.3 - - 14.6 11.3
AI - - - - 1.2 1.5 2.4 3.6 5.1 - - 1.4 1.3
Ag - - - - 0.5 1.2 - - - - - - _
-
-
-
-
Mg 0.1 - 4.6 6.5 - 5.4 - - -

I

Fig. 6. Deformation bands near the surface of the retrieved outer race.

and they indicate the presence of smeared cage material at Regions I1 and IV; see Table 2b for the
analysis report. At Region 11, Ag is also present indicating that when the cage got smeared here the
coating was at least partially intact. No bearing component was found to contain Cr, Si, A1 and
Mg in the amounts detected in Region I11 of the inner race. Particles rich in Si and A1 and containing
Mg were retrieved from the lubricating oil and could be transported to the inner race from some
other source through the lubricant.
The material protruding from the RHS of the race (Fig. 4c-vii) contained more than 7% Cr which
was not found in any of the bearing components. It seems that a component of high chromium
content was severely damaged and hit the inner bearing race. No obvious damage was seen on the
inner race at the location of impact.
Different portions of the retrieved cage, including the inside surface of the holes, showed smears
of steel; an iron content of up to 71 % was found near the surface regions. The retrieved balls showed