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 fixture for selectively masking portions of a gas turbine engine component disposed therein while a workpiece coating is being applied to unmasked portions thereof, predetermined surfaces of the fixture comprising:
an average surface roughness of about 25 Ra or less to minimize the amount of workpiece coating bridging that will occur between the fixture and the gas turbine engine component when the workpiece coating is applied; and
a Rockwell hardness of about 65 Rc or more to ensure the fixture can maintain an average surface roughness of about 25 Ra or less throughout repeated applications of the workpiece coating,
where the predetermined surfaces include at least portions of the surfaces of the fixture proximate the gas turbine engine component where workpiece coating bridging might occur across a gap in a plasma spray coating proceess that is configured to minimize the amount of rework needed on the gas turbine engine component after the gas turbine engine component is coated, and the fixture and the gas turbine engine component disposed therein define the gap that is as small as about 0.020 inches.
2. The fixture of claim 1 , wherein the predetermined surfaces comprise at least any fixture surfaces that will be exposed to workpiece coating when the gas turbine engine component is being coated.
3. The fixture of claim 1 , wherein the fixture is capable of being used in a thermal spray process.
4. The fixture of claim 1 , wherein the fixture is made of A2 tool steel at least partially coated with TiN or TiAIN.
5. The fixture of claim 1 , wherein the predetermined surfaces of the fixture comprise at least one of the following:
(a) an uncoated material having a Rockwell hardness of at least about 65 Rc;
(b) a fixture coating on the surfaces, the coating comprising a Rockwell hardness of at least about 65 Rc; and
(c) a treated material that has been treated to have a Rockwell hardness of at least about 65 Rc.
6. The fixture of claim 5 , wherein the predetermined surfaces have been polished to an average surface roughness of about 25 Ra or less.
7. The fixture of claim 5 , wherein the fixture is made of at least one of: A2 tool steel and 340 stainless steel.
8. The fixture of claim 5 , wherein the fixture coating comprises at least one of TiN and TiAIN.
9. The fixture of claim 5 , wherein the treated material has been treated via at least one of a nitriding process and a plating process.
10. The fixture of claim 1 , wherein the plasma spray coating process is a YSZ plasma spray coating process.