Patent Application
20180044799
The invention relates generally to a non-metallic coating for steel substrates and for coated steel substrates. More particularly, the invention relates to a multi-layer non-metallic coating including at least one protective layer and at least one absorber layer, and to a method and system for forming such a coating on a steel substrate or on a coated steel substrate.
Motor vehicle components are often produced by hot-forming a cold-rolled or hot-rolled steel sheet. Examples of such automotive steel products include vehicle columns, supports, bumpers, rocker panels, fuel tank assemblies, door frames, and components such as parts of the floor of the motor vehicle. Hot-forming is carried out at a temperature greater than 700° C. and often includes hot-stamping the steel sheet. Rapid cooling of the component is then performed in order to improve the mechanical strength and other properties of the finished product.
Unfortunately, uncoated steel substrates are susceptible to scale formation, corrosion and decarburization, which can occur at exposed surfaces of the substrate during hot-forming. These types of surface defects can lead to reduced mechanical strength in the finished product and produce increased wear on the forming tools. Further, these types of surface defects make it more difficult to paint the surface of the component and may lead to poor adhesion of a subsequently applied paint coat.
Various solutions have been suggested for reducing the severity of these types of surface defects. For instance, the hot-formed steel part can be shot-blasted to remove surface corrosion and scaling, but this requires a high degree of energy and may have a negative influence on other properties of the component. Alternatively, the steel substrate may be heated in a controlled atmosphere oven in order to prevent the surface defects from occurring in the first place, but this solution increases the cost and complexity of the system that is used to carry out the hot-forming process. Further alternatively, the steel substrate may be coated prior to being hot-formed. By way of an example, a coating for a steel substrate is disclosed in WO 2013/166429, which includes one to three different layers, each of which is free of metal atoms. The composition of the layers includes at least silicon and carbon, and the total thickness of the coating is not more than about 300 nm.
It would be beneficial to provide a non-metallic coating and method that overcomes at least some of the above-mentioned disadvantages.
In accordance with an aspect of at least one embodiment, there is provided a non-metallic coating for a steel substrate or for a coated steel substrate, comprising: a first layer comprising at least one of a silicon oxide, a silicon nitride, and a silicon oxynitride; and a second layer comprising chromium nitride, the second layer having a thickness between 3 nm and 30 nm, wherein the first layer and the second layer form a stacked-layer structure having a total thickness of not more than 300 nm.
In accordance with an aspect of at least one embodiment, there is provided a coated steel component, comprising: a steel substrate; a non-metallic coating formed on the steel substrate, comprising: a first layer comprising at least one of a silicon oxide, a silicon nitride, and a silicon oxynitride; and a second layer comprising chromium nitride, the second layer having a thickness between 3 nm and 30 nm, wherein the first layer and the second layer form a stacked-layer structure having a total thickness of not more than 300 nm.
In accordance with an aspect of at least one embodiment, there is provided a method for coating a steel component with a non-metallic coating, comprising: providing a steel substrate or a coated steel substrate; depositing a non-metallic coating on the steel substrate or the coated steel substrate, including a first layer comprising at least one of a silicon oxide, a silicon nitride, and a silicon oxynitride; and a second layer comprising chromium nitride, the second layer having a thickness between 3 nm and 30 nm, wherein the first layer and the second layer form a stacked-layer structure having a total thickness of not more than 300 nm.
In accordance with an aspect of at least one embodiment, there is provided a non-metallic coating for a steel substrate or for a coated steel substrate, comprising: a first layer comprising at least one of a silicon oxide, a silicon nitride, and a silicon oxynitride; and a second layer comprising a metal nitride, the second layer having a thickness between 3 nm and 30 nm, wherein the first layer and the second layer form a stacked-layer structure having a total thickness of not more than 300 nm.
The following description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments disclosed, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
The term “coating” is used throughout the description and in the appended claims to refer to a stack of individual layers that is formed on a substrate. The substrate may be a “blank” or a “finished component” that is formed from the blank. The substrate may be a bare steel substrate or a previously coated steel substrate, such as e.g. a zinc plated steel substrate. More generally, the previously applied coating may be a metal coating, a metal alloy coating or a non-metallic coating.
The term “layer” is used to describe a deposited structure that performs a desired function within the coating (e.g. protective layer/absorber layer). A layer may consist of a single stratum or plural strata. The term “sub-layer” is used throughout the description and in the appended claims to identify different strata within a layer. In general, each stratum within a layer is fabricated from a different material.
The term “layer thickness” refers to the material thickness of an identified layer within a coating. When a layer comprises a plurality of sub-layers, the term “layer thickness” as applied to that layer means the total thickness of all of the sub-layer thicknesses.
The terms “coating thickness,” “thickness of the coating,” and “total layer thickness” are used interchangeably to refer to the sum of the layer thickness of all layers within a coating.
The term “non-metallic” is used to describe each of the individual layers in a coating. A layer that is described as being “non-metallic” may also be classified as “free of metal,” which means the layer does not include metal atoms. For instance, as discussed below, the protective layer 1 is non-metallic and is also “free of metal.” On the other hand a layer that is described as being “non-metallic” may contain metal atoms, but it does not exhibit any of the properties that are normally associated with a bulk metal material. For instance, a non-metallic layer does not display the high reflectivity, electrical and thermal conductivity, and ductility characteristics that are typical of a bulk metal material. As discussed below, the absorber layer 2 contains metal atoms but is “non-metallic” because the metal atoms are contained in island structures or because the layer is too thin to behave as a bulk metal material. Of course, a coating that contains only “non-metallic” layers is also described as being “non-metallic.” A “non-metallic” coating or layer may contain unavoidable metal atom impurities. Further, the term “non-metallic” is not intended to exclude semimetals or metalloids, such as for instance silicon.
Referring now to
As is apparent, the ordering of the layers 1 and 2 in coating 12 is different than the ordering of the layers 1 and 2 in coating 10, relative to substrate 3. Of course, the layers 1 and 2 in
Optionally, the layer sequence of the coating 10 or 12 may be repeated one or more times on top of the structures that are shown in
Referring still to
By way of a specific and non-limiting example, the total thickness of the coating 10 or 12 is up to 300 nm. More preferably however the total thickness of the coating is up to no more than about 130 nm. Continuing with the same non-limiting example, the protective layer 1 preferably has a layer thickness of approximately 30-100 nm, and the absorber layer 2 preferably has a layer thickness of approximately 3-30 nm. Of course, the above-mentioned numerical ranges are intended to provide guidance for forming coated steel substrates that are suitable for typical applications encountered in the automotive industry. It is to be understood that some applications may demand coating characteristics that require the deposition of a thicker coating 10 or 12. As already discussed above, a total layer thickness up to about 300 nm is envisaged, but with corresponding reduced savings in cost and time.
Depending on the amount of material (CrN) that is deposited, the absorber layer 2 is applied either in the form of a uniform, thin layer or in the form of island-shaped material clusters. An absorber layer 2 applied in the form of a uniform, thin layer results in a “deck of cards” type structure, in which the protective layer 1 and the absorber layer 2 are distinct layers formed one on top of the other. As a result, there is very little incorporation of the material from one layer into the other layer. On the other hand, an absorber layer 2 that is applied in the form of non-contiguous island-shaped clusters has relatively large interstices between the island-shaped clusters, and these interstices become filled with material of the protective layer 1 when the protective layer 1 is applied to the absorber layer 2 during the formation of the coating.
To optimize the absorption properties of the scale protection layer, “plasmon-based layer paints” are generated. In this connection, island-shaped material clusters play a significant role. The reason for the behavior of metallic island layers lies in the fact that the electrons are freely mobile within the islands, but not between the islands. As the result of a partial and temporary charge shift within the islands, local field intensification occurs, also called plasmon-plasmon interaction. This leads to the result that the electromagnetic radiation is characteristically influenced when passing by this layer. Precisely this influence is absorption intensification, which is implemented in this coating having non-metallic materials. In simplified form, it can be formulated that metallic plasmons are the longitudinal resonance oscillations of the delocalized conduction electrons.
In the case of non-metals, which after all are being used here, what are then involved are the collective oscillations of the valence electrons.
If one applies island-like clusters of the absorber layer 2 to the substrate 3, a very thin layer of about 3 nm is sufficient for achieving the desired properties. Here, too, being metal-free and not integrating the reflective and other characteristic properties of a metal or of an alloy into the layer system is significant.
Referring now to
The coating 10 is obtained when the absorber layer 2 is deposited first, onto the surface of either a bare or previously coated steel substrate. The protective layer 1 is subsequently deposited, either as a single layer or as a plurality of sub-layers.
The coating 12 is obtained when the protective layer 1 is applied first. Applying the protective layer 1 first is practical in order to achieve good adhesion of the thin-layer coating system on the steel substrate 3.
As mentioned above, cleaning the surface to which the coating 10 or 12 is to be applied, using glow discharge, heating or other cleaning of the substrate in a vacuum, is optional. The system for forming such coatings may therefore be simplified, and the cost of such systems is reduced, compared to prior art systems that include components for cleaning the substrate. Beneficially, eliminating the substrate-cleaning step also shortens the production times for forming the coated components. In some cases it is advantageous to carry out the preparation of the steel sheet using plasma cleaning, such as for instance when SiNx is used to form the protective layer directly onto the substrate.
Alternatively, the protective layer 1 is formed using Plasma Supported Chemical Vapor Deposition (PE-CVD) and the absorber layer 2 is formed using sputtering technology. Using PE-CVD to form the protective layer 1 results in a coating that demonstrates excellent scale protection characteristics.
Referring now to
The in-line system comprises at least two vacuum chambers. In the particular system that is shown in
Referring still to
Referring now to
As discussed supra the protective layer 1 and absorber layer 2 may be deposited using sputtering technology. In this case the systems that are shown in
Alternatively, the protective layer 1 is deposited using PE-CVD and the absorber layer 2 is deposited using sputtering technology. In this case the systems shown in
The use of PE-CVD methods brings advantages with it: Activation of the starting compounds in the plasma allows clearly lower temperatures during deposition. In plasma-supported oxide deposition, silane SiH4 and laughing gas N2O are used:
3SiH4+6N20→3SiO2+4NH3+4N2
Plasma deposition of silicon oxide from TEOS is also possible:
Si(OC2H5)4→SiO2+decomposition products
Furthermore, plasma deposition of silicon oxide, utilizing a triode configuration, as in the deposition of plasma nitride, as well, allows adjusting the layer tension. The triode configuration of the plasma reactor is used to better adjust the layer tension. In this way, a high plasma density can be adjusted by way of a high-frequency generator, while acceleration of the ions toward the substrate can be achieved by way of a low-frequency generator.
Alternatively, the protective layer 1 can also be vapor-deposited. For this purpose, SiO2 is evaporated from crucibles, thermally or by means of an electron beam, while the steel plates or the steel strip move through the “vapor cloud” and are coated with SiO2 while doing so. The actual coating process takes place in a chamber.
The steel surface to be coated must be kept dust-free and grease-free before the process. All non-stainless steels are possible as steel substrates.
More generally, a coating according to an embodiment has the following structure: CrN=17 nm, SiOxNy=40 nm and SiO2=12 nm, where 0≦x≦2 and 0≦y≦1.33.
While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
Numerical ranges include the end-point values that define the ranges. For instance, “between X and Y” includes both X and Y, as well as all values between X and Y.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively.
The foregoing description of methods and embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention and all equivalents be defined by the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015204802.0 | Mar 2015 | DE | national |
| 102015204803.9 | Mar 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2016/050298 | 3/17/2016 | WO | 00 |
