Page 182 - Failure Analysis Case Studies II

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Fig. 9. Scanning electron fractograph showing features characteristic of fatigue. x 3600

which is described as a high-temperature, extreme-pressure, corrosion-resistant assembly lubricant.
This was very difficult to remove prior to the laboratory examination, but, clearly, it does not afford
protection to the surface of the bolts. Water seeping across the contact area (joint) of the cover and
body to the drive head bolt locating holes can, therefore, penetrate the anti-seize compound.
A water additive is used for its lubricating and hole cleaning properties, but only if the system is
a closed loop. In addition, the additive would have no corrosion-inhibiting effect on the water. A
medium such as an oil-based red lead primer should be used at the connection joint between the
cover and the body in order to prevent water from reaching the drive head bolts. The torque
tightening of the 32 bolts will cause the compound to “spread” and allow satisfactory sealing of the
mating surfaces.

Fig. 10. Longitudinal section of a bolt thread root showing fine tempered martensite, and no material or
manufacturing defects. Etched in 2% nital. x 285.