Pitting and galling

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Senior Member
Hi there,

I need a mechanical engineer help. Regarding the below sentence:
When this occurs, turbine components made of hardened steel or metal alloys can still break down as a result of extreme wear, scuffing, surface fatigue, pitting and galling.

What is galling in this particular case?

I have no idea about the meaning.

  • Copyright

    Senior Member
    American English
    From Wikipedia: Galling: Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is caused by a combination of friction and adhesion between the surfaces, followed by slipping and tearing of crystal structure beneath the surface. This will generally leave some material stuck or even friction welded to the adjacent surface, whereas the galled material may appear gouged with balled-up or torn lumps of material stuck to its surface.

    More on that link.

    Uncle Jack

    Senior Member
    British English
    I am a mechanical engineer and I cannot improve on the Wikipedia entry Copyright has posted. Two moving parts stick together at a microscopic level, causing the surface of one of them to pull away. The movement doesn't have to be fast like a turbine blade; it can occur when slowly screwing in a bolt.
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