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  for Metal Finishing since 1989
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Effect of Different Coatings on Fatigue Life of Components

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Hi....Sir, I am a student of MS engineering. I am doing a research thesis on the "effects of coating on the fatigue life of components" may any body help me in this regard.

Thanks.

Mntahir
Student - Islamabad, Punjab, Pakistan
2004

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2003

The MFIS CD-ROM reveals dozens of published articles from the metal finishing literature on this subject. You need access to a database, whether printed or computerized, to do a literature search; and then you need to get copies of the relevant articles.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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Regards,

Engr.M N Tahir
Asstt. Manager - Islamabad, Punjab, Pakistan
2004

I am using different types of coatings on Ferrous and aluminum alloys. I have come to know that coatings decrease the fatigue life of components. Can anybody comment on this? How can fatigue life be restored after plating.

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One thing is fatigue and another is hydrogen embrittlement (HE). In the first case the failure occurs over time due to cyclic stresses and most always cracks appear before it happens; the cause is residual stress and high hardness in the coating. The HE attacks mostly hardened steel and produces a sudden failure without prior notice; is not related to the hardness or stress in the deposit but rather to the low bath efficiency during deposition and low permeability of the plate. Both factors combine to produce hydrogen gas that cannot escape so it gets entrapped in the substrate. The remedies are specific for the combination of base metal and plating type but in general involve heat treatment.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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You need to decide what properties you are trying to achieve, which will dictate the type of finish you will need, which will in turn dictate the type of pre and post treatments you will need. Are you plating or anodising aluminium? If anodising, subsequent sealing will restore much of the fatigue characteristics, but other properties are affected (paint adhesion for CAA/SAA, or wear resistance for hard anodising).

Trevor Rowlands
Aircraft Component Manufacturer - Melbourne, Victoria, Australia
2004

There are a large number of factors that influence the fatigue life of parts. One important thing is the surface finish of the parent material. The finer the finish, the greater the fatigue life. The amount of stress in the deposit is another. Highly stressed deposits such as chrome will drastically reduce fatigue life, and can be compensated by prior shot peening. Lower stress deposits like cadmium do not need this type of pretreatment.

adv.