Table 2-2. Propeller Defects - CONT
Discoloration due to synthetic engine oils should not be confused with heat
discoloration. Additives in Specification MIL-L-23699 oil react with steel surfaces
to form a brownish color stain. This stain is not detrimental and should not be
A part which breaks or decomposes into small objects.
Distortion is caused by forces which twist the piece from its original shape.
Damage not having the same geometric center.
Loss of metal from the surface by mechanical action of foreign objects, such as
grit or fine sand. The eroded area will be rough and may be lined in the direction
in which the foreign material moved relative to the surface.
The breaking loose of small pieces of metal or coated surfaces, which is usually
caused by defective plating or excessive loading.
A break through the entire thickness of the material.
An area worn by rubbing actions.
A rapid oxidation of metal surfaces caused by cyclic back-and-forth movement
of closely fitted parts in the presence of oxygen. It is characterized by rusty
surfaces ranging from black (well bonded) to a fairly bright brick red color (often
loosely bonded or even free particles).
A severe condition of chafing or fretting in which a transfer of metal from one
part to another occurs. It is usually caused by a slight movement of mated parts
having limited relative motion and under high loads.
Damage which appears smooth and glossy.
A furrowing condition in which a displacement of metal has occurred (a torn
effect). It is usually caused by a piece of metal or foreign material between
close moving parts.
A recess or channel with rounded and smooth edges usually caused by faulty
alignment of parts.
Shallow depressions in the functional surfaces where metal has been displaced
but not removed. They are usually rounded, having the shape of the foreign
particle, and the original surface finish can still be seen in the depressions.