ES2597814A1 - System of metallic glass coatings with aluminum base alloys with improved corrosión and wear resistance properties (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

System of metallic glass coatings with aluminum base alloys with improved corrosión and wear resistance properties. The invention relates to a system comprising metallic glass coatings based on aluminum, which have low porosity, good adhesion and excellent properties against wear and corrosión in the chloride environment, and its processing procedure using cold projection technology. Furthermore, the invention relates to the use of said coating system as a component or a part of a component of a protection system used in the automotive, aerospace, aeronautics, transport, naval and mining industries. (Machine-translation by Google Translate, not legally binding)

Description

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METAL GLASS COATING SYSTEM WITH ALUMINUM BASED ALLOYS WITH CORROSION AND WEAR RESISTANCE PROPERTIES

IMPROVED

DESCRIPTION

The invention relates to a system comprising aluminum-based metal glass coatings, which have low porosity, good adhesion and excellent anti-wear and corrosion properties in the environment of chlorides, and to their processing process using cold projection technology . In addition, the invention relates to the use of said coating system as a component or a part of a component of a protection system used in the automotive, aerospace, aeronautics, transportation, naval and mining industries.

STATE OF ART

The metallic glasses (acronym in English MG of metallic glasses) with its lack of crystalline structure have attracted the attention of the scientific community due to its already known advantages, such as mechanical resistance and better magnetic and electrochemical properties over its crystalline counterparts. Great variety of MG has been discovered in recent years based on alloys of the following main elements Fe, Ni, Zr, Cu, Al, Mg, Co and also on the basis of rare earth elements. Among the diversity of MGs, Al-based alloys exhibit low density, good mechanical strength and good corrosion resistance as it is a lightweight material, with potential for the aerospace industry and in applications in the automotive industry. Unfortunately, Al-based MGs are difficult to manufacture due to their low capacity to form vortex systems (acronym in English GFA of glass forming ability) and the need for a protective atmosphere for their production. Many efforts have been made in the design of the composition of the alloys and in the manufacturing technique to produce Al-based MGs with an improved GFA. The most successful compositions consist of Al-TM-RE ternary alloys, where TM is a transition element (i.e., Ni, Co or Fe) and RE an element of the rare earth group (i.e., La, Ce, Di or Y). In fact, rods made of MG on the basis of Al with a diameter of 1 mm were obtained by simultaneously replacing Ni and Y with Co and La respectively in the Al-Ni-Y system [BJ Yang, J.H. Yao, Y.S. Chao, J.Q. Wang, E.Ma, Philosophical Magazine 90-23 (2010) 3215-3231and BJ Yang, JHYao, YS Chao, J.Q. Wang, E.Ma, Scripta Materialia 61 (2009) 423-426]. The improved GFA of the

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Ternary composition is due to the function of the insertion atoms, the ER atoms are larger and facilitate the formation of glass, while the TM atoms help to have a more efficient atomic packing, favoring an energetically more stable amorphous state. Despite the progress in the composition of the alloys, the size of the MG pieces based on Al remains a great limitation for their practical applications.

The cold projection technology (acronym in English CGS of Cold Gas Spray) within the whole thermal projection processes has become one of the best options to develop MGs as a coating material. The advantages of the CGS process consist in being a solid state process; This means that the amorphous state of the MGs, previously manufactured as a powder material, is preserved after deposition. The coating is produced from the high speed impact of the powder and its consequent plastic deformation. In this way, parts of any size ranging from millimeters to meters can be coated, taking advantage of the properties of the MGs on the surface and of a metal alloy on the substrate. In fact, partially amorphous Ni-based and Fe-based thermal spray coatings are used industrially as protective coatings because of their better physical and chemical properties, as already mentioned [
http: //www.nakayama- amorphous.co.jp/en/ and
http://scopertainc.com/]. Recently, alloys based on crystalline but partially amorphous Al have been deposited by CGS. Despite the high porosity 2%, low hardness 3.36 GPa and the low thickness of 250 microns, this alloy showed interesting properties such as wear protection coatings [D. Lahiri, PK Gill, S. Scudino, C. Zhang, V. Singh, J. Karthikeyan, N. Munroe, S. Seal, A. Agarwal, of surfaces and coatings Tecnologia 232 (2013) 33-40 and SB Pitchuka, B Boesel, D. Lahiri, C. Zhang, A. Nieto, S. Sundararajan, A. Agarwal, Surface and Coatings Technology 238 (2014) 118-125]. However, improving the wear and corrosion performance of these coatings is still a challenge.

DESCRIPTION OF THE INVENTION

Metal glasses (acronym in English MGs of metallic glasses) based on Aluminum are alloys with low capacity for glass formation, therefore, conventional thermal projection techniques, such as Plasma Spray, High Velocity Oxy-Fuel, Flame Spray or Warm Spray , are not suitable for producing coatings of this type of materials. Conventional thermal projection techniques produce high rates of oxidation of the particles in flight or the cooling of the impacted particles is too slow to

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the formation of a metallic glass, a fact that leads to coatings with poor performance due to partial crystallization or oxidation of the particles. The cold projection technique is therefore advantageous because the acceleration gas is nitrogen, an inert gas that protects the particles against oxidation; and the low working temperatures prevent the crystallization of the coatings.

Thus, the present invention consists in the use of the cold projection technique in order to obtain a coating system comprised of an Al-based metal glass and a suitable substrate with which the Al-based metal glass has a good adhesion .

The present invention has an aluminum based metal glass coating system consisting, for example, of a metal substrate and an aluminum based metal glass coating which is formed of deformed and welded grids between them, said grids are formed to in turn by an amorphous phase and a-aluminum nanocrystals, where said a-aluminum nanocrystals are embedded in said amorphous phase matrix.

These coating systems have low porosity, good adhesion and excellent anti-wear and corrosion properties in chloride-rich environments.

Therefore, the systems can be used as a component or part of a component of a protection system used in the automotive, aerospace, aeronautics, transportation, marine and mining industries that may be exposed to corrosive environments and generate wear while a low weight is required.

An advantage of having a coating system is that it is easy to replace. By cold projection technique the repair and replacement of the coating can be carried out on site. In addition, the coating fully utilizes the best properties of the applied material, that is, metal glass or nanocomposite metal glass, to protect the component against corrosion and wear.

A first aspect of the present invention relates to a coating system characterized in that it comprises:

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• A coating consisting of metallic glass particles of an aluminum base alloy flattened and welded together, said particles consist of an amorphous phase and, optionally, of a-aluminum nanocrystals, in which said a-aluminum nanocrystals are embedded within said amorphous phase;

• A substrate.

In a preferable embodiment, the particles of the metal-based glass coating Al are ternary alloys of formula

Al-TM-RE

in which TM is a transition metal selected from the list consisting of Ni, Co and Fe, and RE is a rare earth element selected from the list consisting of La, Ce, Gd and Y.

In another preferred embodiment of the present invention, the coating has a porosity fraction volume between 0.1% and 2%. It is well known that low porosity improves coating performance. Highly porous coatings lead to poor corrosion resistance because they can allow the electrolyte to reach the substrate material and offer poor wear resistance.

In a preferred embodiment, the coating has a thickness greater than 25 ^ m. Although, preferably it has a thickness between 100 pm and 2000 ^ m.

The substrate on which the coating is deposited must be adequate, that is, that the metal-based glass coating Al has a good adhesion to the substrate.

Preferably the substrate is metallic.

Examples of substrates in the present invention are aluminum, other aluminum alloys and steels.

As mentioned before, the coating system of the invention comprises

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• A coating consisting of metallic glass particles based on flattened and welded together.

• Said particles consist of amorphous phase and, optionally a-Al, in which said a-Al nanocrystals are embedded in said amorphous phase;

In the coating system of the invention, the amorphous phase extends between 100% and 70% by volume.

In another preferred embodiment of the invention, the flattened particles of the metal-based glass coating Al are constituted by amorphous phase, this means that the coating is 100% formed by an amorphous phase.

Another embodiment refers to the flattened particles of metal glass in Al base which are constituted by an amorphous phase and a-aluminum nanocrystals. In this case, said a-aluminum nanocrystals are embedded in said amorphous phase.

The a-aluminum nanocrystals are in a volume percentage of less than 30%.

Preferably, the a-aluminum nanocrystals are of sizes ranging from 5 to 50 nm.

A second aspect of the present invention relates to a process for obtaining the coating system in which the process comprises the following steps:

a) preparation of base metal glass Al in powder form where metal glass particles have a composition in the following system:

Al-TM-RE

in which TM is a transition metal selected from the following list: Ni, Co and Fe, and RE is an element of the rare earth family selected from the following list: La, Ce, Gd and Y; said particles consist of amorphous phase and, optionally, nanocrystalline a-aluminum;

and b) deposition of the powder obtained in step a) on a substrate by cold projection under the following projection parameters:

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• gas temperature between 250 ° C and 600 ° C,

• gas pressure between 15 bar and 50 bar,

• and the projection distance between 10 to 100 mm.

In addition, the amorphous aluminum-based powder is formed by spherically or irregularly shaped particles that have an average particle size distribution of between 10 pm and 100 m.

The last aspect of the invention refers to the use of the coating system of the invention as a component or part of a component of a protection system used in the automobile, aerospace, aeronautics, transportation, naval and mining industries.

Unless otherwise defined, all the technical and scientific terms used here have the same meaning as that commonly understood by an ordinary expert in the technique to which this invention belongs. Methods and materials similar or equivalent to those described herein may be used in the practice of the present invention. Throughout the description and claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. Additional objects, advantages and features of the invention will be apparent to those skilled in the art upon examination of the description or can be learned through the practice of the invention. The following examples and figures are provided by way of illustration and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 Characteristics of atomized base powders At amorphous a) Surface morphology, b) distribution of grid size, c) X-ray diffraction patterns (XRD acronym for X-ray diffraction), d) Differential scanning calorimetry (acronym in English DSC of Differential Scanning Calorimetry) of the base powder Al amorphous.

FIG. 2. a) Efficiency of deposition of the coatings under different projection conditions, b) thickness, hardness and porosity of the coatings obtained by cold projection under the best projection conditions, c) cross-sectional structure of the Al-based coatings -MG in the best process conditions, d) free surface of Al-based MG coatings.

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FIG. 3 a) X-ray diffraction pattern (XRD) of the amorphous powder and the coating, b) Differential scanning calorimetry (DSC) of the Al-based MG powder (dashed black) and of the coating (continuous line).

FIG. 4 X-ray diffraction pattern of the coating heated to 10K / min up to a) 275 ° C and b) 300 ° C.

FIG. 5 a) Wear rate after the wear test for MG coatings based on Al at different applied forces b) depending on the friction coefficient (COF) and c) COF depending on the sliding distance at different loads applied to MG coating based on Al.

FIG. 6 a) Micrograph acquired by scanning electron microscopy (SEM) of the worn surface at 10N a), and b) indicating the size of the wear products and the shape of the slide track at 10N load.

FIG. 7 Worn surface of the MG coating based on Al a: a) 10 N, b) at 15 N, c) at 20 N, d) at 10 N and at smaller increases, (e) - (j) EDS mapping of the wear track of (d) showing the worn surface rich in the following elements, e) Al, f) O, g) Ni, h) Co, i) La, j) Y.

FIG. 8 a) Potential open-circuit (EOC) curves as a function of time for Al-based MG coatings and Al-7075 substrate. b) and c) Typical potentiodynamic polarization cycles of Al-based MG coatings and Al7075 substrate in 0.6 M NaCl.

EXAMPLES

Preparation of initial powder and coatings

The amorphous base powder of nominal composition Al88Ni6Y4.5Co1La05 was manufactured by gas atomization and subsequently screened in order to obtain a particle size distribution from 20 to 40 micrometers before projection.

A commercial cold projection equipment (CGS) Kinetics® 4000/17 kW (Impact Innovations, Ampfing, Germany) with a maximum working pressure of 40 bar and a temperature of 800 ° C was used to deposit the coatings on substrates of the AI alloy -7075-T6 with a flat geometry (100 x 50 x 5 mm). The substrates of Al-7075-T6 were roughed up using grain SiC paper 240. The CGS equipment used allows to establish different projection parameters such as projection distance, gas pressure and gas temperature. Details on the projection parameters are presented in Table 1. For convenience, the coatings have been prepared under different cold projection conditions and are denoted as C1 to C8, respectively.

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Table 1. Parameters of the projection process for the different series studied.

 Gas used (N2) Projection distance (mm)

 Condition

 Temperature (° C) Pressure (bar)

 C1

 300 30 10, 20, 30

 C2

 300 35 10, 20

 C3

 350 35 10, 20

 C4

 350 40 10, 20, 30

 C5

 400 25 10, 20, 30, 40

 C6

 400 30 10, 20, 30, 40

 C7

 400 35 10, 20, 30, 40

 C8

 400 40 10, 20, 30, 40, 50

Characterization of projection powder and coatings

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Initial powder characterization was carried out using a laser diffraction equipment (LS 13 320 laser diffraction, Beckman Coulter, Inc., 250 S. Kraemer Blvd, Brea, CA) to verify the distribution of the particle size after sieving. Scanning electron microscopy (SEM Jeol JSM 5310, JEOL, Inc., Peabody, MA) was used to reveal initial powder morphology. The atomic structure of the initial powder was studied by X-ray diffraction (DRX) (PANalytical X'Pert PRO MPD, PANalytical Almelo, The Netherlands). The DRX unit is equipped with a monochromatic Cu Ka X-ray source (A = 1,54056 A; 40 kV; 100 mA). X-ray diffraction patterns were taken in the range of 10 ° <20 <100 ° with a step of 0.017 ° and the time was 300 seconds per stage of

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measurement. The characteristic temperatures and the crystallization challenge (AHx) were determined by differential scanning calorimetry (DSC-1, Mettler-Toledo SAE, Barcelona, Spain), at a heating rate of 10 K / min.

The deposition efficiency of the process was calculated by measuring the increase in substrate mass after deposition and normalized by the mass of the projected powder during deposition. The cross section of the coatings was characterized by means of an optical microscope (MO) (Leica DMI 5000 M, Leica Microsystems, GmbH). The image analysis software, Image J, was used to calculate the porosity (ASTM E2109-01 standard) of the cross section. Vickers hardness measurements were performed on a Vickers microdurometer (Matsuzawa MXT CX-1, Matsuzawa Co., Ltd, Akita-shi, Akita, Japan). At least 10 indentations were made on the surface of the polished cross section of each coating. The load in the hardness tests was set at 100 gF and the residence time was 10 s. DRX and DSC analyzes of the coatings were performed using conditions similar to the analyzes of the initial powders.

Wear tests: wear tests were carried out after selecting the optimized coatings, that is, with the best deposition efficiency and the best mechanical properties. The coatings were characterized before and after the wear test, SEM was used with an X-ray dispersive energy spectroscopy detector (EDS) and the amorphous structure was checked by XRD. The slip wear test was performed with a ball tribometer (BOD), following the ASTM G99-04 standard. An aluminum oxide ball was used, a relative sample velocity of 124 rpm, a total length of 1,000 meters and different loads of 10N to 20N were used. Humidity and temperature were kept below 30% and 25 ° C, respectively. The loss of volume and recreation of the wear path was done with the Leica TCS-SE confocal equipment.

Corrosion tests: the corrosion behavior of MG based coatings Al was evaluated by measurements of potentiodynamic polarization in 0.6 M (3.5 wt.%) NaCl solution (ASTM G31-72 standard). The open circuit potential (EOC as a function of time) and the polarization curve (PC) were measured using an EG&G Princeton Applied potentiostat-galvanostat Research model 2,273 in a three-electrode cell set. The potential was scanned from 1.3 V to -1.3 V (vs. Ag / AgCl (3.0 M KCl) with a scan rate of 0.5 mV / s. Platinum and Ag / AgCl were used as the against electrode and reference electrode, respectively.

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Potentiostaticas were carried out on the unpolished surface of the coatings acting as a working electrode with a surface of 1 cm2. All electrochemical tests were performed at room temperature. The potentials mentioned in this work refer to standard Ag / AgCl electrode. The surface of the coating exposed to the NaCl solution was analyzed by means of SEM / EDS after the corrosion tests.

Characterization of the initial powders

MG powder based on Al showed a spherical and uniform morphology, as seen in Figure 1 (a). The powder had a monomodal particle size distribution and an average particle size of 32 ± 10 microns, Figure 1 (b). The XRD analysis of the powder showed a broad spectrum typical of an amorphous material and the presence of small peaks corresponding to phase a-Al, Figure 1 (c). The DSC curves of the studied powder exhibit three crystallization processes that can be associated with three crystallization temperatures, TP1, TP2 and TP3 at 231 ° C, 342 ° C and 400 ° C, respectively (Figure 1 (d)) . The crystallization start temperature (Ton) is also shown at 224 ° C. The transition glass temperature (Tg) in the DSC curve cannot be observed. This is due to the superposition of the glass transition with the first crystallization peak in Al-based MGs. The crystallization in three separate processes is typical in Al-TM-RE amorphous alloys, where TM is a transition element (i.e. , Ni, Co or Fe) and RE is an element of the rare earth group (ie, La, Ce, Di or Y). For the alloy studied, the first peak corresponds to the precipitation of nanocrystals a-Al, the results of the second crystallization peak is the growth of the nanocrystals a-Al and the formation of the intermetallic phases, (Ni, Co) 3Al4 and Al2CoY . Complete crystallization occurs when the dust is heated even more above the third peak leading to the disappearance of the amorphous matrix.

Characterization of the coatings

The deposition efficiencies of the projected coatings with conditions C1 through C8 are shown in Figure 2 (a). The efficiency clearly increased when the temperature of the gas also increased, since the temperature of the gas not only contributes to the acceleration of the particles due to the expansion of the fluid flow of gas in the convergent-divergent duct, but also, to the heating of the particles in flight. The effect of increasing the temperature of the material above Tg causes softening

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thermal of the particles, which allows the metal glasses to deform homogeneously, and a greater union between particles is generated. The highest deposition efficiency was obtained for conditions C8, corresponding to the highest gas pressure and temperature. Gas pressure plays a secondary role that contributes to increasing the kinetic energy of flying particles. The greater kinetic energy of the particles results in a greater energy available for deformation during impact. This is in accordance with the results shown in Figure 2 (a) and Figure 2 (b) for condition C8, where the particles subjected to sufficient temperature and kinetic energy showed the highest deposition efficiency (85%) at a projection distance of 30 mm. On the other hand, when the distance was set to a maximum of 40 mm, the deposition efficiency was reduced due to the loss of temperature and kinetic energy. Observing Figure 2 (b), condition C8 with a projection distance of 30 mm corresponds to the optimum projection conditions for Al88Ni6Y45Co1La05 metal glasses that lead to coatings with thicknesses of around 400 microns, a Vickers hardness of 220 Hv , and a volumetric porosity fraction around 1.6%.

The cross section and the free surface of the MG coatings in base Al are shown in Figure 2 (c) and Figure 2 (d) for the best projection conditions. MG coatings based on Al obtained by cold projection exhibit a dense layer structure with the presence of pores, which are identified in the figures as the dark regions located between the flattened particles. The unpolished top surface of the coating shows slightly deformed particles, and also deformed and fractured particles. The different modes of deformation of the particles are related to the deformation rates experienced by each individual particle depending on their average size, temperature and impact speed, where the small particles arrive colder, but at a speed greater than The biggest particles. Thus, the deformation velocities at impact are higher for particles with smaller sizes, which leads to their fracture. In contrast, large particles undergo slight deformation due to deformation rates and impact temperatures that promote homogeneous deformation. The fracture is also attributed to the impact between metal glass particles regardless of their size. The particle-particle impact leads to a higher rate of deformation of the particles.

In Figure 3 (a), the X-ray diffraction pattern of the MG base coating Al is compared with respect to the initial powder diffraction pattern. There are no signs of new phases in the coatings obtained. In Figure 3 (b), the DSC curves of the initial powder and the coating are shown. In the case of MG coatings based on Al, a new crystallization peak is observed compared to the initial powder. The four crystallization peaks in the coating have a temperature called, TP1, TP2, TP3 and TP4, corresponding to 231 ° C, 289 ° C, 342 ° C and 400 ° C, respectively. In order to investigate the changes experienced by the Al-based metal glass during the projection process, the enthalpies of crystallization were calculated, which are listed in Table 10 2.

Table 2. Enthalpy of crystallization of the initial powder of the metallic glass Al88Ni6Y45Co1La05. The corresponding percentage of amorphous phase Vamorfa was calculated with respect to an amorphous tape of similar composition and the grain size (D) of a-Al (200) and a-Al- (220) was derived 15 from the Scherrer equation .

 Sample

 AHcrystallization (J / g) Total AH (J / g)% Vamorpha Crystalline phase at D (nm)

 pi

 P2 P3 P4 200 220

 Initial powder

 24.8 - 43.7 44.4 -112.9 82.4 a-Al 65.2 56.8

 Coating

 13.5 19.5 29.5 36.8 -99.3 72.6 a-Al 68.4 54.6

Interestingly, it was estimated that 82.4% of the initial powder is constituted by amorphous phase, but the total enthalpy of crystallization of the coating was about 10% less than 20 in the initial powder.

The average diameter of the nanocrystals of a-Al was evaluated from the width in half of the peaks of the DRX pattern according to the Scherrer equation,

kX

ficosd

equation 1.

where k is a constant, at the radiation wavelength and 0 the diffraction angle. Based on this equation, particles of nanometric scale were found both in the powder as well

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as in the coatings after the projection. There were no significant changes in the average diameter of the nanocrystals in the coatings. In addition, the volume crystallized fraction from the DRX pattern was evaluated in both the initial powder and the coatings. Both results, the crystallized fraction by volume and the size of the particles, indicate that the precipitation of a-Al is insignificant during the CGS process. To reveal the nature of the crystallization products of the first two DSC peaks, the coatings were treated linearly at 10 Kmin "1 at the end of both peaks, 275 ° C and 300 ° C. The DRX patterns of the treated samples were shown in Figure 4. Both samples correspond to phase a-Al superimposed on an amorphous halo.The coating treated above the second peak in the DSC shows a higher crystalline fraction in volume since the intensity of the diffraction peaks is much higher, therefore, the crystallization products of both DSC peaks are the a-Al phase, which indicates the decomposition of the amorphous matrix of the initial powder into two amorphous phases during the CGS process.

From the results presented, it is understood that the amorphous structure of metal glasses based on Al undergoes significant changes during the CGS projection process as a result of the temperature experienced by the particles. The separation of the amorphous phase has already been reported in glasses of the Al-TM-RE family [29-32]. This phenomenon consists in the decomposition of the initial amorphous phase into two different amorphous phases that coexist before crystallization. Phase separation often occurs when at least two of the constituent elements of the alloy have a positive mixing heat [29]. In our MG based Al, the heat of mixing between pairs of elements is negative. The phase separation in metal glasses with enthalpy of negative mixture has been explained as a consequence of the short-range atomic order (SRO) that modifies the free energy curve and generates a maximum local, producing phase separation [33,34] .

The DRX and DSC before and after the projection process do not reveal the precipitation of new crystalline phases, while the a-Al nanocrystals present in the initial powder remain at a similar size and volume fraction after deposition. The formation of two different amorphous phases, in the present study for Al-based MG, are induced as a consequence of the increase in thermal energy during the projection process. Both amorphous phases are rich in Al and therefore, their primary crystallization leads to the precipitation of a-Al. The second amorphous phase precipitates at a higher temperature probably due to the difference in the composition. This

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Thus, the Al-based metal glass coatings of the present invention consist of a double amorphous phase matrix (about 82% by volume) with a-Al nanocrystals embedded in the amorphous phases.

Wear test: The wear speed is shown in Figure 4 (a), and calculated using the following equation:

~ v w. , -

Q = - equation 2.

x N ^ S

where Q is the wear rate in mm3N'1m'1, Vw is the wear volume (mm3) calculated from the sliding profile by confocal microscopy, N the applied load (N) and S the total sliding distance (m ).

The wear resistance of the MG base Al coatings shows about 200% lower wear than compared to the Al-7075-T6 substrate at 10 N of applied load. The wear resistance of the MG base Al coatings is better than the Al alloy that acts as a substrate even if the applied load is increased up to 20 N. Therefore, the Al-based metal glass shows superior wear resistance than Al crystalline alloys, demonstrating that cold projection metal glass coatings can offer excellent surface protection against wear on sliding surfaces.

The average friction coefficient (COF) and the wear rate as a function of the normal load for the MG base Al coating is shown in Figure 4 (b). The error bar at each point indicates the standard deviation of three repeated trials. The behavior of the COF as a function of the sliding distance for different normal loads applied is also shown in Figure 4 (c). It is interesting to note that both the COF and the wear rate have a strong increase when the applied load increases from 10 N to 20 N. The higher COF obtained from the increase in the applied load suggests a dependence on the wear mechanism in normal load. For the three forces applied, COF has an initial filming period, where it increases to a maximum value. This first step occurs within the first 200 meters, for this particular case, and is often associated with the presence of a medium / high contact pressure during the initial stage of sliding on rough surfaces. In the present invention, the coatings were polished to a mirror surface with a roughness value Ra below 0.8 microns. Without

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However, taking into account the lack of volumetric homogeneity of the coatings, it is possible to assign the initial filming period to the high contact pressure caused within the volumetric heterogeneities, leading to high contact friction and wear loss, mainly due to localized fracture of the surface layer in the weakest regions, such as fords between the splat / splat surfaces and inter-splat regions, and the accumulation of wear residues on the worn surface, Figure 5 (a) and (b). After this period of shooting, the COF decreases and becomes almost constant due to the smoother and more homogeneous surface and the elimination of accumulated wear residues.

In order to further investigate the wear mechanism of the Al base MG coatings, the wear profile was analyzed for each case by means of SEM / EDS as shown in Figure 6 (a) - (j). The worn surfaces of the coatings, in all loading conditions, show signs of plastic deformation and the presence of residual particles, Figure 6 (a) - (c). Despite its low ductility in tension, Al base MG alloys have good ductility and toughness. As the normal load of 10 N and 20 N increases, more extensive abrasive grooving occurs, with larger and deeper grooves, and the presence of a large number of residual particles. It is evident that the wear mechanism of the Al base MG coatings of the present invention is dominated by grooving with limited surface shedding of splats in all loading conditions. Repeated plow fatigue and fracture of the weakest regions are the reason for the production of waste residues. The size and shape of the residues in the slide profile at a 10N load, in Figure 5 (b), remained almost equal when the applied load was increased, but as shown in Figure 6 (a) - ( c), the number of waste increased as the load increased. The largest amount of waste is in line with the intensification of abrasive wear and higher wear speeds at 20N. The EDS analysis of the wear profile showed that the worn surface was rich in elements present in the metal glass, Figure 6 (d) - (j); but the presence of oxygen only on the worn surface suggests oxidation of the MG base Al due to friction. In fact, the temperature on the sliding surface is an important factor to consider for metal glass. Typically, the ambient temperature, the average or surface temperature of the material, and the sudden increase in temperature are the typical temperatures involved in the process of wear by surface sliding. The room temperature can be easily controlled and maintained as in the present invention, at room temperature. The average temperature of the material generally does not have great influence due to heat dissipation,

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but it could be important for the wear mechanism if the sudden rise in temperature is too high. The sudden rise in temperature represents the surface temperature located in the contact regions that exceeds both the average temperature of the material and the ambient temperature. The sudden increase in the highly localized temperature leads to a global increase in the temperature that is captured in the average surface temperature. This coincides with the high plastic deformation and the oxidation observed in the wear profile, which could be generated by an increase in the average temperature. However, there are no signs of adhesive waves and no areas of molten material such as vein patterns in the wear profile, suggesting that the average surface temperature was well below the characteristic temperatures of the metal glass alloy. DSC analysis of the wear profile was performed and no change in crystallization was detected in relation to the projected red coatings.

Corrosion test: electrochemical tests showed the resistance of the coatings in chloride environment. In Figure 7 (a), the initial decrease in open circuit potential is a consequence of the initial penetration of the electrolyte through the surface and due to chemical dissolution. After 20h of testing, the open circuit potential became stabilized at -0.688 ± 0.005V for the MG base Al coating, and at -0.819 ± 0.005V for the Al7075-T6 alloy, Figure 7 (a). However, the Al7075-T6 alloy curve shows a large number of oscillations that indicate the destruction and formation of a layer of corrosion products on the surface. The typical potentio-dynamic polarization curve of the base Al MG and Al7075-T6 coating in a 0.6 M NaCl solution (3.5%) is shown in Figure 7 (b). Clearly, the MG base Al coatings are spontaneously passivated with a potential of the order of -0.65 V and exhibit a passive region until the transpassive solution above -0.4 V, while the Al7075-T6 alloy shows values well below -0.8 V for the beginning of the passivation region and the transpassive solution represented by the increase in current density, starting around -0.7 V. To reveal the stability of passivation films after of the anodic polarization, negative scans were recorded during polarization measurements. In Figure 7 (c) - (d), the cycle of hysteresis in the polarization curves shows that the current density in the negative scan was much closer to that of the passivation current density for the samples of the Al-base MG coatings, in the order of up to 10 "5 A / cm2. Normally, the change in inverse current density in dipole curves narrows due to the stability of the passive film. One more hysteresis cycle

17

Small polarization curves suggest a better stability of the passive film. This is in accordance with Figure 7 (c), where pitting corrosion is observed in the Al-7075 alloy just before the transpassive phenomenon begins. Therefore, the present potentio-dynamic results suggest that more stable films are formed in the Al base MG coating with respect to the Al-7075-T6 alloy.

Electrochemical parameters (corrosion current densities (Icorr) and corrosion potentials (Ecorr) from polarization curves), and open circuit potentials (EOCP) depending on the type of material are shown in Table 3.

10

Table 3. Collected values of electrochemical parameters measured in the present invention and from the literature.

 Material

 [NaCl] / M Ecorr vs Ag / AgCl Icorr (mA) Reference

 Al-based MG Coating

 0.6-0.718 2.68 Present invention

 Al-based amorphous / nano coating

 0.01 -0.666 1.96 Surface and Coatings Technology 232 (2013) 33-40.

 Al-based amorphous / nano coating

 0.1-0.830 6.26 Surface and Coatings Technology 238 (2014) 118-125.

 Alloy 6061

 0.01 -0.622 9.87 Surface and Coatings Technology 232 (2013) 33-40.

 Alloy 6061

 0.1 -1,271 28.7 Surface and Coatings Technology 232 (2013) 33-40.

 Alloy Al-7075

 0.6 -0.849 0.75

 Al-99.99% pure

 0.1-0.771 0.298 Materials Review 47 (2002) 86-112.

15 Al-amorphous / nanocrystalline, Al-pure and Al-6061 alloy data were taken from the literature [See references in the table]. The coatings obtained from MG base Al have a novel character compared to the other materials, although a higher concentration of chloride was used in this work. This result is due.

mainly to the greater amount of amorphous phase in the present MG base Al coating.

Claims (13)

5 10 fifteen twenty 25 30 1. A coating system with features that include: • A coating consisting of metallic glass particles of a base alloy Al flattened and welded together, said particles consist of an amorphous phase and, optionally of a-aluminum nanocrystals, in which said a-aluminum nanocrystals are embedded within said amorphous phase; • And a substrate. 2. The coating system according to the preceding claim, wherein the metal base glass particles Al of the coating are ternary alloys of formula Al-TM-RE wherein TM is a transition metal selected from the list consisting of Ni, Co and Fe, and RE is a rare earth element selected from the list consisting of La, Ce, Gd and Y. 3. The coating system according to any one of claims 1 or 2, wherein the coating has a porosity volume fraction between 0.1% and 2%. 4. The coating system according to any one of claims 1 to 3, wherein the coating has a thickness greater than 25 ^ m. 5. The coating system according to the preceding claim, wherein the coating has a thickness between 100 pm and 2,000 m. 6. The coating system according to any one of claims 1 to 5, wherein the substrate is metallic. 7. The coating system according to the preceding claim, wherein the substrate is selected from the list consisting of aluminum, aluminum alloys and steels. 5 10 fifteen twenty 25 30 35 8. The coating system according to any one of claims 1 to 7, wherein the aluminum base metal flattened particles of the coating consist of an amorphous phase. 9. The coating system according to any one of claims 1 to 7, wherein the base metal flattened particles Al base of the coating consist of an amorphous phase and a-aluminum nanocrystals, wherein said nanocrystals of a- aluminum are embedded within said amorphous phase. 10. The coating system according to the preceding claim, wherein the a-aluminum nanocrystals are of sizes ranging from 5 to 50 nm. 11. The coating system according to any of claims 9 or 10, wherein the a-aluminum nanocrystals are in a volume percentage less than 30%. 12. A process for obtaining the coating system according to any one of claims 1 to 8, wherein the process comprises the following steps: a) preparation of an amorphous powder based on aluminum consisting of particles of metal base glass Al of the formula Al-TM-RE in which TM is a transition metal selected from the list consisting of Ni, Co and Fe, and RE is a rare earth element selected from the list consisting of La, Ce, Gd and Y; said particles consist of amorphous phase and, optionally a-aluminum nanocrystals, according to any of claims 8 to 11; Y b) deposit the powder obtained in step a) on a substrate by the cold projection technique under the following projection parameters: • processing gas temperature between 250 ° C and 600 ° C, • processing gas pressure between 15 bar and 50 bar, • and projection distance between 10 to 100 mm. 13. The method according to the preceding claim, wherein the Al base metal glass particles that form the amorphous powder have an average particle size distribution of between 10 pm and 100 m. Use of the coating system according to any one of claims 1 to 11 as a component or part of a component of a protection system used in the automobile, aerospace, aeronautics, transport, naval or mining industry.