Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2000-01-04
2001-11-27
Beck, Shrive (Department: 1762)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C427S248100, C427S255500, C427S255110, C427S255280, C427S240000, C427S288000, C427S294000, C118S730000, C204S192160
Reexamination Certificate
active
06322671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the field of coating processes by the method of physical and chemical vapor deposition (PVD and CVD), allowing the improvement of operational properties of the coatings, by delivering to the coatings quasi-plasticity behavior and can be used for the formation of protective metal and non-metallic coatings on substrates of the components, operating under environmental degradation mechanisms, e.g., for applying high-temperature coatings on gas-turbine blades.
2. Background
Usually, the following formation process is used to obtain coatings on substrates by the method of vaporization and deposition in a vacuum. A substrate is placed into a vacuum device chamber, having a source of material for vaporization (e.g., a titanium cathode, vaporized by the ionic-arc plasma method in a nitrogen media, resulting in titanium nitride being deposited onto the substrate surface); the necessary vacuum is produced, then the material is vaporized and deposited onto the substrate surface in the form of an integral flow (i.e., the coating is formed under the integral build-up front), the deposition is continued until a determined thickness of the coating is obtained.
The considered methods for coatings production are used in various fields of technology, where it is necessary to transfer to surfaces some special properties, providing higher resistance to wear, corrosion, erosion, high-temperatures, etc., than that of the material the surface is made. The creation of highly effective protective coatings, with minimal negative influence upon the degradation resistance of substrates, is vital in such fields as energy generating engines, aircraft engines, machine and ship building. Existing coating formation methods do not allow the production of coatings which meet the present requirements. In particular, the low quality of the present coatings is explained by unsatisfactory quasi-plasticity properties of the deposited materials. With this, the quasi-plasticity properties of the coatings depend upon the thickness of the coatings. For example, for various materials and particular deposition conditions, there exist particular threshold thickness values, which, when exceeded, significantly lower the quasi-plasticity properties. For example, in the case of titanium nitride obtained by the ionic-plasma method, this thickness value makes about 5 microns, which requires a special layer being applied to ensure a proper thickness. (E.g., International Patent WO N 90/02218: “PLASMA METHOD FOR COATING AN OBJECT WITH A HARD METAL”.) With this, the quasi-plasticity properties of the materials, when the critical thickness of coatings is not exceeded, also remain unsatisfactory.
At the same time, the range of the necessary thickness values for protective coatings lies between several microns and several hundred microns, i.e., the requirements of the coating thickness exceed the ability to provide quasi-plasticity, which results in a lower quality of the coatings and poor characteristics of the protected substrates.
It is known that with all other conditions being equal, the properties of a coating are determined by the presence of defects, the type of the structure and the thickness. In the general case for the methods being considered, the defects are appearing and growing in number during the coating formation, due to the interaction of structural elements of the coating within the growth process. Along with this, while the coating thickness increases, the negative effect of defects increases. The other cause of the low quality of coatings is in the orientation of the coating structural elements not being optimal from the functional viewpoint.
As it follows from the above statement, in order to provide a higher quality of coatings, it is desirable to meet the following three objectives:
Decrease the formation of defects and the negative interaction of structural elements during the coating formation process;
Obtain a predetermined structure and orientation of the structural elements of the coating;
Decrease the sensitivity of the coating and the coated substrate to the thickness of the coating.
It is known that various methods of coatings production in a vacuum form different structural types: a columnar structure, an equal-axis structure, a cone-like structure, etc. However, the problems of defects formation, including the dependence of defects on the thickness of the coating, are common for all cases.
To illustrate the idea, the above-mentioned problems of quality improvement are considered using the example of the class of coatings, having a columnar structure, with such a coating being taken as a prototype coating, together with a prototype method for analysis.
The prototype: a protective coating formed by integral build-up front by the method of PVD, providing a columnar structure.
The drawbacks of the prototype: low quality, unsatisfactory quasi-plasticity properties, high density of defects, non-optimal structure and orientation of structural elements, and sensitivity of properties to the thickness of the coating.
The causes of the drawbacks:
Defects appearing due to interaction of the structural elements (grains and crystals) of the coating during the growth process;
A columnar structure, oriented perpendicular to the substrate surface, which, as a rule, is non-optimal.
The usual columnar structure for this class of protective coatings diminishes their operational properties. The columnar structural elements, located perpendicular to the substrate surface, make borders, which are also oriented in a perpendicular manner to the substrate surface. Thus, the mechanical strength of such coatings is determined, in the final analysis, by the strength of the bonds between the columnar elements. In the conditions of high temperatures and aggressive media, such borders are good conductors of alien aggressive chemical elements, leading to coatings destruction, which is aggravated also by mechanical stresses. Naturally, cracks are appearing in such coatings, acting as tension concentrators, leading to the fast destruction of a protected substrate.
SUMMARY OF THE INVENTION.
The present invention comprises versions of formation of integral protective coatings with improved quasi-plasticity behavior, which formation includes the following steps:
1. Preparing of substrate surface for a protective coating application;
2. Locating the substrate into a vacuum vapor deposition device chamber in front of the deposited material source;
3. Providing an action for deposition of the material onto the substrate surface in the form of multiple separated-in-space deposition zones;
4. Providing an action for constant migration of said multiple deposition zones over the substrate surface during the whole process of coating formation, while uniformly distributing the material over the substrate surface;
5. Creating a vacuum necessary for condensation of the deposition material over the substrate surface in a vacuum device chamber;
6. Vaporizing and deposition of the material over the substrate surface in the shape of constantly migrating separated-in-space zones, making an integral, uniform coating of a necessary thickness, and if necessary, providing a following (final) treatment of the coating, e.g., re-crystallization annealing in a vacuum.
It is an object of the present invention to:
To create conditions allowing an additional degree of growth freedom for the structural elements, so as to diminish the degree of interaction of the coating structural elements being formed, hence diminishing the formation of defects;
To form a predetermined coating structure and orientation of the structural elements, so as to provide the most efficient resistance to the deterioration factors.
Generally, the optimal orientation of columnar structural elements of a coating would be when such elements are parallel to the substrate surface; however, such coatings do not exist at present.
The particular ways in which these objectives are met, together with other object
Barr Michael
Beck Shrive
IONICA, LLC
LandOfFree
Method for formation of protective coatings with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for formation of protective coatings with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for formation of protective coatings with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597011