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Film thickness and tolerance

Does film thickness affect your tolerance?

A PVD film grows on every surface the source can see, so a diameter gains twice the film and a bore loses it. For most tolerances that is far below the noise. This works out which side of the line you are on.

Published film thickness by code

Typical film thickness for each chamber deposited SurfTech coating code
Code	Chemistry	Typical thickness
SurfTech 3012	CrN	1 to 4 µm
SurfTech 4000	B4C	1 to 3 µm
SurfTech 4253	B4C / MoS2	1 to 3 µm
SurfTech 5000	MoS2	0.5 to 2 µm
SurfTech 6020	TiN	1 to 4 µm

Published typical ranges for each material system, not certified SurfTech figures. The value for your part comes from the data sheet issued with the quote. Thickness is not published yet for SurfTech 3010, SurfTech 4200, SurfTech 4656, SurfTech 6012, SurfTech 6120, SurfTech 6212 or SurfTech 9200. Data sheets for those are available on request.

PTFE is not in this table. It is sprayed and cured rather than deposited in the vacuum chamber, and at 12 to 40 microns it sits an order of magnitude away from the films above. If you are considering PTFE on a dimensioned feature, ask rather than calculate.

What this page will not give you

It will not give you a pre-coat undersize target. Grinding a feature undersize to allow for a film is the one thing on this page that cannot be undone, and the published thickness range is four times wide from end to end. A part machined to allow for four microns that comes back with one is permanently oversize, in a material you cannot weld up. Pre-coat targets are agreed at part review, against a thickness SurfTech commits to for your job.

It will not answer confidently for a bore. Deposition is line of sight. A film grows on every surface the source can see, and how far it reaches down a bore depends on the diameter, the depth and how the part is fixtured. Anyone who gives you a number for that from a web form is guessing.

It does not say pass or fail. There are two answers here. Either your tolerance is loose enough that film thickness is not the thing to worry about, or it is tight enough to be worth engineering. Both are useful. Neither is a certification.

Send the drawing

Send the tightest tolerance on the print and which surfaces stay uncoated. SurfTech confirms the thickness and the masking before the job runs.

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