Non-stick masking fixtures and methods of preparing same
Non-stick fixtures for selectively masking portions of a workpiece during application of a workpiece coating are described herein. These fixtures have predetermined surfaces thereon having an average surface roughness of about 25 Ra or less and a Rockwell hardness of about 65 Rc or more. The controlled average surface roughness ensures that these fixtures are non-stick with respect to the workpiece coating being applied to the workpieces disposed therein. The controlled Rockwell hardness ensures that the desired average surface roughness can be maintained throughout repeated use of the fixture in harsh coating environments. These fixtures reduce the workpiece coating bridging that occurs between the fixture and the workpiece, and also reduce the amount of overspray that occurs on the workpiece, thereby minimizing the amount of handwork and/or rework that is necessary after the workpiece is coated. This improves process cycle times and yields significantly.
1. A method for preparing a fixture for selectively masking a workpiece during application of a workpiece coating, the method comprising the steps of:
preparing predetermined surfaces of the fixture to an average surface roughness of about 25 Ra or less; and
ensuring that the predetermined surfaces are hard enough to maintain the average surface roughness throughout repeated applications of workpiece coating.
2. The method of claim 1 , wherein the preparing step comprises polishing the predetermined surfaces.
3. The method of claim 1 , wherein the ensuring step comprises at least one:
(a) making at least the predetermined surfaces of the fixture from a material having a Rockwell hardness of at least about 65 Rc;
(b) coating at least the predetermined surfaces of the fixture with a fixture coating to harden at least the predetermined surfaces of the fixture to a Rockwell hardness of at least about 65 Rc; and
(c) treating at least the predetermined surfaces of the fixture to harden at least the predetermined surfaces of the fixture to a Rockwell hardness of at least about 65 Rc.
4. The method of claim 3 , wherein the coating step comprises applying the fixture coating via at least one of physical vapor deposition and chemical vapor deposition.
5. The method of claim 3 , wherein the fixture coating comprises at least one of TiN and TiAlN.
6. The method of claim 3 , wherein the treating step comprises hardening at least the predetermined surfaces of the fixture via at least one of a nitriding process and a plating process.
7. The method of claim 1 , wherein the predetermined surfaces comprise at least a portion of any fixture surfaces where bridging of workpiece coating may occur between the fixture and the workpiece.
8. The method of claim 1 , wherein the predetermined surfaces comprise at least any fixture surfaces that will be exposed to workpiece coating when the workpiece is being coated.
9. The method of claim 1 , wherein the fixture is capable of being utilized in a thermal spray process.