Re: Why the Internal stresses from shrinkage develop in coatings

Posted by Gordon England on April 25, 2003 at 03:08:29:

In Reply to: coating stress posted by harpreet on April 03, 2003 at 18:13:04:

: 1. Why the Internal stresses from shrinkage develop in coatings and these stresses increase with increased coating thickness.

: 2. Why the stresses in coating are more severe in hard metals or ceramics.

Hi Harpreet

Imaging a molten particle striking a cold surface, attaching itself then cooling. Most materials shrink on cooling so a tensile stress will develop in the particle and a compressive stress in the surface restraining the particle.
As the coating is built up each particle adds an additional stress component.

Hard metals or ceramics do NOT necessarily produce coatings more highly stressed than softer materials.


Hard 1%C steel or 13% Cr steel can produce very thick low stress coatings compared to soft low carbon steel or austenitic stainless coatings which have very limited coating thickness limitations and are highly stressed.

Coating stress is primarily due to the amount of shrinkage of the material. Other factors such as porosity, microcracking etc. have an effect, but are more process related rather than the material.

Regards Gordon

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