Ideal Surface Roughness
04-26-2007, 06:12 PM,
#1
Ideal Surface Roughness
Hi

Have a limited experience in the surface engineering field, and everytime that surface roughness was mentioned i had the idea that a very smooth surface can lead to coating detachment. In my current job i encountered a company that uses PACVD that says that a smooth substrate mean good adhesion. can someone coment on this?

Thanks

Regards
Reply
04-28-2007, 05:26 PM,
#2
RE: Ideal Surface Roughness
Hi ruskasinthehouse

Sign0016 to the Surface Engineering forum.

In processes like painting, powder coating and thermal spray where the coating does not alloy, diffuse or metallurgically bond with the substrate material, surface texture is an extremely important factor with respect to bonding (increases surface area and promotes mechanical keying). With processes that form metallurgical bonds, the surface texture tends not to be so critical.
Reply
05-05-2007, 09:44 AM,
#3
RE: Ideal Surface Roughness
Hi,
PACVD is a vapor phase deposition process, whereas in thermal spraying the molten or semi-molten particles are spray deposited onto the substrate.CVD requires heating of workpiece to high temperature thus allowing diffusion of elements from coating material to the substrate.The diffusion results in a strong metallurgical bond.For comparitively weak mechanical bond in thermal spraying depends, it is essential to take care of all the factors enhancing the bond strength including the surface roughness, as pointed out by Gordon.
Ram
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