Gas Screen Coating Process for Substrate Pre-Heating
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Solution Overview
Problem
In physical vapor deposition processes, premature deposition of coating material during pre-heating can alter the chemistry and microstructure of the thermally grown oxide and debit the performance of components, particularly in gas turbine engine applications where maintaining chemical stoichiometry and adherence of the coating is critical.
Innovation Solution
A gas screen is established using increased oxygen gas flow or other gases to shield the substrate from premature deposition of volatilized coating material during pre-heating, and later, back-pressure is applied to collimate and increase the deposition rate of the coating plume during the actual deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pre-heating is conducted in an oxygen-containing environment to grow oxide scale and maintain chemical stoichiometry, then the chemical composition is improved, but premature deposition of volatilized coating material occurs on the substrate
Solution Approach 1:
The patent divides the pre-heating process into two distinct stages: a first pre-heating stage without oxygen supply to prevent premature deposition, and a second pre-heating stage with oxygen supply to grow oxide scale and maintain chemical stoichiometry. This temporal segmentation allows each objective to be achieved in its appropriate phase without interference
Solution Approach 2:
The patent performs preliminary heating of the substrate and coating material without oxygen before the actual pre-heating process. This preliminary action prevents premature deposition by eliminating volatilized coating material early, while preserving the coating material's ability to form oxide scale later when oxygen is introduced
2Strength
If the substrate is heated to high temperature to ensure coating adherence, then coating adherence is improved, but volatilized coating material deposits prematurely on the substrate
Solution Approach 1:
The heating process is segmented into phases: initial heating without oxygen to reach target temperature while preventing deposition, followed by oxygen introduction for oxide scale growth. This ensures the substrate achieves necessary temperature for adherence without causing premature coating material deposition
Solution Approach 2:
The patent uses oxygen as a controlled intermediary that is introduced only after the substrate reaches appropriate temperature. Oxygen acts as the mediating element that enables oxide scale formation for adherence while being timed to prevent premature deposition caused by high-temperature volatilization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces premature deposition, maintains chemical stoichiometry, and enhances the adherence and performance of the ceramic coating by controlling the gas flow and pressure to ensure a focused, dense coating plume, thereby improving the coating process efficiency and component performance.
Implementation Method 1
Physical vapor deposition ('PVD') is one common method for depositing a coating, such as a metallic coating or a ceramic coating, on a substrate
Implementation Method 2
One type of PVD process utilizes an electron beam gun to melt and evaporate a source coating material contained within a crucible
Implementation Method 3
utilizes an electron beam gun to melt and evaporate a source coating material
Implementation Method 4
The evaporated source material condenses and deposits onto the substrate
Data Source
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Figure 3
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AI summary
A method for use in a coating process includes pre-heating a substrate in the presence of a coating material and shielding the substrate during the pre-heating from premature deposition of the coating material by establishing a gas screen between the substrate and the coating material. An apparatus for use in a coating process includes a chamber, a crucible that is configured to hold a coating material in the chamber, an energy source operable to heat the interior of the chamber, a coating envelope situated with respect to the crucible, and at least one gas manifold located near the coating envelope. The at least one gas manifold is configured to provide a gas screen between the coating envelope and the crucible. A second manifold provides gas during a later coating deposition to compress a vapor plume of the coating material and focus the plume on the substrate to increase deposition rate.