EP0576366A1 - Metallic coatings consisting of amorphous wear- and corrosion resistant alloys, process for obtaining these alloys and use as wear resistant coatings of hydraulic material - Google Patents

Abstract

The finishes of the present invention consist essentially of metal alloys having the general formula: TaCrbZrcBdMeM'fXgIh(I) in which a+b+c+d+e+f+g+h=100 atomic percent; T is Ni, Co, Ni-Co or any combination of at least one of Ni and Co with Fe, wherein 3<Fe<82 at. % and 3<a<85 at. %; M is one or more elements of the group consisting of Mn, Cu, V, Ti, Mo, Ru, Hf, Ta, W, Nb, Rh, wherein 0<e<12 at. %; M' is one or more rare earths, including Y, wherein 0<f<4 at. %; X is one or more metalloids of the group consisting of C, P, Ge and Si, wherein 0<g<17 at. %; I represents inevitable impurities, wherein h<1 at. %, and 5</=b</=25, 5</=c</=15, and 5</=d</=18. Powders obtained from these alloys that are deposited on substrates by thermal projection provide finishes having increased hardness in addition to high ductility and excellent resistance to corrosion. The finishes are suited for applications including hydraulic equipment.

Description

The present invention relates to metallic coatings based on amorphous alloys resistant to wear and corrosion, the methods for obtaining these coatings and their applications to the production of antiwear coatings, in particular for hydraulic equipment.

In the description which follows, these coatings will be mainly studied in their applications on metallic substrates. It is obvious that, without departing from the scope of the present invention, they are also of particular interest when they are applied to non-metallic substrates such as wood, paper and synthetic substrates.

There are researches in many fields to solve the problems posed by phenomena of wear by abrasive erosion, scratches and friction in aggressive media and cavitation phenomena. These problems arise with special acuity when it comes to hydraulic equipment such as turbines.

• Dureté élevée leur permettant de résister aux phénomènes d'érosion de frottement et de rayures
• Bonne ductilité leur permettant de résister aux chocs et aux faibles déformations.
• Structure homogène leur assurant un bon comportement à la corrosion.

In general, the materials currently used are hard but in return they are fragile and users are looking for materials with the following properties:

• High hardness allowing them to resist the phenomena of friction erosion and scratches
• Good ductility allowing them to resist shocks and small deformations.
• Homogeneous structure ensuring good corrosion behavior.

Currently, the materials available, whether steels with high mechanical characteristics, stellite, ceramics ... do not have all these properties. In particular, if they resist corrosion well, they do not have sufficiently high mechanical properties.

One of the solutions for obtaining materials having a satisfactory compromise between these contradictory properties consists in using metal alloys of amorphous structure obtained by rapid cooling.

The amorphous alloys used to date are mainly in the form of small ribbons obtained by a casting method or in the form of very thin deposits obtained by electrochemical methods.

The thermal projection methods and for example that of the blown arc plasma have not so far made it possible to obtain completely amorphous alloys at the level of X-ray diffraction in the form of very thick powder deposits (> 0.5 mm) on surfaces up to several square meters.

Among the various amorphous alloys currently known, it is the metal-metalloid alloys based on iron (Fe-B or Fe-Cr-P-B alloys) which give the best results from the point of view of mechanical characteristics. None of these alloys, however, makes it possible to satisfy the contradictory requirements sought for high mechanical strength, corrosion resistance and ductility.

The object of the present invention is to provide amorphous metallic coatings combining with high mechanical characteristics a certain ductility, a high crystallization temperature, a good ability to be released from the residual manufacturing constraints by means of a heat treatment of stress relaxation without causing a significant change in structure and brittleness, good corrosion resistance, including in the presence of halogens, made from alloys capable of being amorphizable for cooling rates of the order of 10 ^{5 ° K / sec.} , these coatings can be obtained on thicknesses from 0.03 to 1.5 mm on large surfaces.

The inventors have discovered that the ease of amorphization can be obtained by combining the action of the different states of positive or negative size of certain constituent elements with respect to the basic constituent elements, and in particular by playing on the combined action of B and Zr on a Fe - Ni and / or Co. matrix

On the other hand, a low concentration of metalloids and the absence of intermetallic compounds with a high melting point makes it possible to obtain satisfactory ductility. The presence of Zr allows a high crystallization temperature to be obtained. Finally, a suitable dosage of Cr and Zr makes it possible to fight against corrosion.

   dans laquelle a + b + c + d + e + f + g + h = 100 % en nombre d'atomes
   T est Ni, Co, ou tout choix de plus de l'un de ces éléments associé à Fe, avec : 3 < Fe < 82 at et 3 < a < 85 % at.
   M est un ou plusieurs éléments d'addition pris parmi la liste : Mn, Cu, V, Ti, Mo, Ru, Hf,Ta, W, Nb, Rh avec :   0<e<12%at.
   M' est une ou plusieurs terres rares, Yr inclus, avec : 0<f<4 % at.
   X est un ou plusieurs métalloïdes choisis parmi C, P, Ge et Si avec : 0<g<17 % at.
    et I représente les impuretés d'élaboration inévitables avec : h < 1% at.The wear-resistant and corrosion-resistant amorphous metal coatings according to the invention are therefore characterized in that they essentially consist of alloys having the following general formula: $${\text{T}}_{\text{at}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

in which a + b + c + d + e + f + g + h = 100% in number of atoms
T is Ni, Co, or any choice of more than one of these elements associated with Fe, with: 3 <Fe <82 at and 3 <a <85% at.
M is one or more addition elements taken from the list: Mn, Cu, V, Ti, Mo, Ru, Hf, Ta, W, Nb, Rh with: 0 <e <12% at.
M ' is one or more rare earths, Yr included, with: 0 <f <4% at.
X is one or more metalloids chosen from C, P, Ge and Si with: 0 <g <17% at.
and I represents the inevitable processing impurities with: h <1% at.

We also have:
5 ≦ b ≦ 25
5 ≦ c ≦ 15
5 ≦ d ≦ 18

The powders of these alloys are obtained by atomization and, for particle sizes <100 μm, the grains have a completely amorphous structure by X-ray diffraction.

The thermal spray deposition method allows reproducibility of deposition and structural conditions.

The alloys used for the amorphous metallic coatings resistant to wear and erosion according to the invention have numerous advantages compared to the alloys of the prior art. First of all, these are easily amorphizable alloys due to the simultaneous presence of boron, an element whose atomic dimension is smaller than that of T atoms, and of Zr, larger than T atoms.

Note also the introduction of other elements favoring the tendency to amorphization, such as rare earths and / or metalloids.

In addition, the crystallization temperature of these alloys is remarkably high, when compared to that of alloys of the prior art, such as Fe-B alloys and derived alloys (such as Fe - B - C, Fe - B - Si ).

This effect, which can be attributed to the presence of zirconium, can be further increased by the addition of refractory elements (such as Mo, Ti, V, Nb, Rh ...) or metalloids.

The combined effects of chromium and zirconium make it possible to obtain excellent resistance to corrosion, an effect which can be further reinforced by the addition of various elements, in particular Rh, Nb, Ti, rare earths and phosphorus.

Finally, these are essentially ductile metallic glasses in a sufficiently low metalloid concentration range, namely:
b + g ≦ 24 at%. The alloys obtained then resist satisfactorily the embrittlement which usually follows in other alloys the heat treatments at the crystallization temperature.

In the general formula (I) indicated above, the choice of the element T makes it possible to distinguish different families of alloys satisfying the criteria of the present invention.

   dans laquelle a + b + c + d + e + f + g + h = 100 % en nombre d'atomes.
   M, M', X, I représentent les mêmes éléments que ceux mentionnés précédemment pour la formule (I), les compositions étant celles indiquées ci-dessus.If T is nickel, we can first of all distinguish the family (II) which corresponds to the formulation: $${\text{Or}}_{\text{at}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

in which a + b + c + d + e + f + g + h = 100% in number of atoms.
M , M ' , X , I represent the same elements as those mentioned above for formula (I), the compositions being those indicated above.

   dans laquelle : 0 ≦ a + a' ≦ 85 at %
   tous les autres symboles présentant la même signification que précédemment.Another family of alloys (III) according to the invention consists of alloys of the family (II) above in which part of the nickel atoms has been replaced by iron, namely: $${\text{Or}}_{\text{at}}{\text{Fe}}_{\text{at}}{\text{'Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

where: 0 ≦ a + a '≦ 85 at%
all other symbols having the same meaning as above.

   dans laquelle : 0 ≦ a + a" ≦ 85 at %, les autres symboles ayant la même signification que dans la formule (I).The substitution of part of the nickel of the family (II) above by cobalt makes it possible to obtain the alloys of general formula (IV): $${\text{Or}}_{\text{at}}{\text{Co}}_{\text{at''}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

in which: 0 ≦ a + a "≦ 85 at%, the other symbols having the same meaning as in formula (I).

   dans laquelle : 0 ≦ a +a' + a'' ≦ 85 at %.We can finally distinguish a last family of general formula (V): $${\text{Or}}_{\text{at}}{\text{Fe}}_{\text{at'}}{\text{Co}}_{\text{at''}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

where: 0 ≦ a + a '+ a''≦ 85 at%.

The following examples will make it possible to better understand the present invention, the characteristics which it presents and the advantages which it is capable of providing.

Example 1: Elaboration of alloys corresponding to the general formulation of family (II)

Alloys corresponding to the formulation of family (II) have been prepared in the liquid state from the constituents, taken separately. For this, fragments of the elements, of commercial purity, were alloyed in the liquid state in a cold hearth furnace placed under helium. The components were heated by high frequency currents. After melting, these alloys are introduced into the inductor of a tape casting machine consisting of a copper wheel 250 mm in diameter with a tangential speed of 35 m / sec. The enclosure containing the wheel is in a helium atmosphere. The crucible is made of quartz with an orifice 0.8 mm in diameter. The injection pressure of the liquid metal is 0.5 bar. The temperature of the liquid metal is measured by optical pyrometry on the upper face of the liquid.

The concentration, in atom%, of the chemical elements is as follows:
50 ≦ Ni ≦ 75 0 ≦ Mo ≦ 5
5 ≦ Cr ≦ 25 0 ≦ Hf ≦ 5
5 ≦ Zr ≦ 15 0 ≦ Si ≦ 5
5 ≦ B ≦ 15 0 ≦ La ≦ 4

A more precise chemical analysis gives:
Ni ₅₈; Cr₂₀; Zr₁₀; B ₁₀; Mo _{2, an} alloy which has a melting temperature (Tf₀) measured by optical pyrometry of 1127 ° C and a hardness Hv₃₀ of the order of 480.

Example 2: Elaboration of alloys corresponding to the general formulation of the family (III)

Alloys corresponding to the formulation of family (III) were developed and obtained in the form of ribbons in an identical manner to that which was done for obtaining the alloys of Example 1.

The concentration, in atom%, of the chemical elements is as follows:

A more precise chemical analysis gives:
Fe₅₁; Ni₁₈; Cr ₈; Zr ₁₀; B ₁₂; Mo _0.3 ; If _0.5 ; Hf _0.2 , an alloy which has a melting temperature (Tf₀) measured by optical pyrometry of 1100 ° C and an Hv₃₀ hardness of 585.

Or:
Fe ₆₅; Ni₁₀; Cr ₅; Zr ₈; B ₁₀; Ti₂, an alloy which has a melting temperature (Tf₀) measured by optical pyrometry of 1080 ° C and an Hv₃₀ hardness of 870.

Example 3: Elaboration of alloys corresponding to the general formulation of the family (IV)

Alloys corresponding to the formulation of family (IV) were developed and obtained in the form of ribbons in an identical manner to that which was done for obtaining the alloys of the preceding examples.

The concentration, in atom%, of the chemical elements is as follows:

A more precise chemical analysis gives:
Co ₆₅; Ni₁₀; Cr ₅; Zr ₁₂; B ₈, an alloy which has a melting temperature (Tf₀) measured by optical pyrometry of 1020 ° C and an Hv₃₀ hardness of 550.

Example 4: Elaboration of alloys corresponding to the general formulation of the family (V)

Alloys corresponding to the formulation of family (V) were developed and obtained in the form of ribbons in an identical manner to that which was done for obtaining the alloys of the preceding examples.

The concentration, in atom%, of the chemical elements is as follows:

A more precise chemical analysis gives:
Fe ₃₆; Co₁₄; Ni ₁₇; Cr ₁₃; Zr₇; B ₇; C₃; If _0.3 ; P _2.7 , an alloy which has a melting temperature (Tf₀) of 1065 ° C and an Hv₃₀ hardness of 685.

Example 5: Elaboration of alloys corresponding to the general formulation of the family (V)

Alloys corresponding to the formulation of family (V) were developed and obtained in the form of ribbons in an identical manner to that which was done for obtaining the alloys of the preceding examples.

The concentration, in atom%, of the chemical elements is as follows:

A more precise chemical analysis gives:
Fe ₁₆; Co₁₆; Ni ₂₀; Cr ₁₀; Zr₁₀; B ₁₄; Si₁₄, an alloy which has a melting temperature (Tf₀) of 1080 ° C and an Hv₃₀ hardness of 1430.

• Fig 1 à 7 sont des courbes de diffraction aux rayons X dans lesquelles les valeurs 2 O sont portées en abscisse et l'intensité I en ordonnée
• Fig 8 est une courbe de recuit isotherme dans laquelle le temps (en heures) a été porté en abscisse et la température (en °C) en ordonnée
• Fig. 9 est une courbe de recuit anisotherme dans laquelle la vitesse de chauffage (en °C.mn⁻¹)a été portée en abscisse et la température de début de cristallisation (en °C) en ordonnée.

The following examples bring together the results obtained on the ribbons and powders of chemical compositions described in the previous examples, with reference to the appended schematic drawing in which:

• Fig 1 to 7 are X-ray diffraction curves in which the values 2 O are plotted on the abscissa and the intensity I on the ordinate
• Fig 8 is an isothermal annealing curve in which the time (in hours) has been plotted on the abscissa and the temperature (in ° C) on the ordinate
• Fig. 9 is an anisothermal annealing curve in which the heating rate (in ° C.mn⁻¹) has been plotted on the abscissa and the temperature at the start of crystallization (in ° C) on the ordinate.

Example 6

• d'une part par la valeur élevée de la température de cristallisation T_x1 qui est par exemple:
  • pour l'ex. 2   T_x1 = 545°C
  • pour l'ex. 3   T_x1 = 570°C
  • pour l'ex. 4   T_x1 = 560°C
    pour une vitesse de chauffage de 20°K / min.
• d'autre part, par exemple pour la composition : Fe ₂₀ ; Co₂₀ ;Ni ₂₈ ;Cr ₁₂; Zr₁₀; B ₁₀, par le fait qu'un traitement thermique de 3 heures à 400°C ne fait pas apparaître par diffraction aux rayons X de modification de la structure amorphe initiale.

The ribbons corresponding to the compositions indicated above have a very high thermal stability which can be verified:

• on the one hand by the high value of the crystallization temperature T _x1 which is for example:
  • for the ex. 2 T _x1 = 545 ° C
  • for the ex. 3 T _x1 = 570 ° C
  • for the ex. 4 T _x1 = 560 ° C
    for a heating rate of 20 ° K / min.
• on the other hand, for example for the composition: Fe ₂₀; Co₂₀; Ni ₂₈; Cr ₁₂; Zr₁₀; B ₁₀, by the fact that a heat treatment of 3 hours at 400 ° C. does not reveal by X-ray diffraction a modification of the initial amorphous structure.

EXAMPLE 7 Corrosion Resistance of Alloys Obtained in the Form of Ribbons

• Potentiel de dissolution statique et dynamique
• Résistance de polarisation autour du potentiel de corrosion en mode potentiodynamique et / ou en mode galvanodynamique
• Intensité du courant de corrosion.

To characterize this outfit, the following parameters were measured:

• Static and dynamic dissolution potential
• Polarization resistance around the corrosion potential in potentiodynamic mode and / or in galvanodynamic mode
• Intensity of the corrosion current.

• H₂SO₄ 0,1 N
• NaOH 0,1 N
• NaCl à 3 % de concentration dans l'eau.

These parameters have been determined in the following environments:

• H₂SO₄ 0.1 N
• 0.1 N NaOH
• NaCl at 3% concentration in water.

For example, for the alloy: Fe ₆₀; Ni ₁₀; Cr ₁₀; Zr ₈; B ₁₂

Example 8

The nuances of families (II) to (V) were atomized in an atomization tower having an Alumina-Zirconia crucible and using a He-Argon mixture to atomize; powders are obtained whose grain size is between 20 and 150 μm.

For a particle size <100 μm, the examination of the structure of these grains, by X-ray diffraction (Kα line of Cu) shows a completely amorphous structure.

For example, for a composition by weight% of:
Fe _20.5 ; Ni _28.2 ; Co _20.9 ; Zr _16.2 ; Cr _11.4 ; B _2.4
the diffraction peak is 35 ° <2 O <55 °. For a recording speed of 4 minutes, for example we obtain a curve such as that shown in Figure 1

The curve of FIG. 2 likewise represents the recording of the X-ray diffraction for a composition by weight% of:
Fe _54.2 ; Ni _17.4 ; Zr _17.2 ; Cr _11.6 ; B _2.27

Example 9

The alloys powders of families (II) to (V) were deposited on various metallic substrates such as structural steel, stainless steels, copper-based alloys, by a thermal spraying method, and for example by the method of arc plasma blown under controlled atmosphere and temperature.

These sprayed powders have a particle size between 30 and 100 μm. The thicknesses, deposited on a sanded substrate, are between 0.03 and 1.5 mm. The coated surfaces are covered over several square meters.

The X-ray diffraction patterns represented by the curves of FIGS. 3 (thickness 0.1 mm), 4 (thickness 0.2 mm), 5 (thickness 0.3 mm), 6 (thickness 0.4 mm) and 7 (thickness 0.5 mm) carried out under the same conditions as those described in Example 8 demonstrate the totally amorphous structure, on the surface and in the thickness, of these deposits.

These powder deposits can also be followed by cryogenic cooling under the conditions described for example in the document FR - A 83 07 135.

Example 10

The deposits are made under the conditions described in Example 9. However, according to one embodiment of the method according to the invention, instead of working in a controlled atmosphere, in order to prevent any oxidation during the spraying of the molten powders, the single path of the molten particles is protected by an annular jet of nitrogen, concentric with the plasma jet carrying the particles, and of dimensions slightly greater than this. The deposits can then be carried out in the open air, under partial protection of nitrogen.

In the case of very thick parts, the thermal mass of the part may be sufficient to provide cooling allowing the deposit to have an amorphous structure. This avoids the cryogenic cooling step.

Example 11 - Study of the thermal stability of powders and deposits.

On the deposits corresponding to the chemical analyzes relating to families (I) to (V) the isothermal and anisothermal anneals show the excellent thermal stability of the amorphous alloys. The curves represented in FIG. 8 correspond to a composition in at%:
Fe ₂₀; Ni ₂₈; Co ₂₀; Cr ₁₂; Zr ₁₀; B _10.

The following table gives the correspondence with the concentrations by weight :

Isothermal anneals define the stability domains of amorphous (A) and crystallized (C) structures for a given time and temperature.

The curve represented in FIG. 9 illustrates the results for the anisothermal anneals which define the start of the crystallization temperature as a function of the heating rate.

These results show the excellent stability of amorphous coatings up to very high temperatures, which is a very important characteristic of the invention.

Example 12 -

It was possible to determine the exceptional mechanical characteristics shown by the deposits obtained according to the present invention, whether it be hardness-ductility or tribological behavior.

For example for the composition in at%:
Fe ₂₀; Ni ₂₈; Co ₂₀; Cr ₁₂; Zn ₁₀; B _10,
"pion-disc" tests were carried out measuring the average coefficient of friction between the material and a diamond or alumina indenter; a value of the dry friction coefficient is obtained of the order of 0.11 when the deposit has undergone a 3 hour tempering at 400 ° C. Examination of the indentor trace in the deposit shows that, if there are cracks, they are of the ductile type.

On a deposit of the same chemical analysis but crystallized, the average coefficient of friction is higher by approximately 5% and one highlights, during the examination of the trace of the indentor, cracks of fragile type.

These observations are confirmed by the standard scratch test in which, up to applied pressures of the order of the breaking limit, no cracking is revealed.

Example 13

The deposits of thickness of the order of 0.5 mm obtained by the thermal spraying method according to the invention have, in the raw deposition state, a percentage of porosity of the order of 8% measured by treatment d 'picture.

This porosity rate can be reduced to around 0 by shot peening the deposit from carbon steel or stainless steel balls with a diameter between 1 and 1.6 mm for a defined peening intensity (Halmen de la Sté Metal Improvment) from 16 to 18 and a recovery rate (Metal Improvment method) of 600%.

This result is confirmed by the study of permeability of the deposit by electrochemical method highlighting, for severe corrosion conditions as indicated above, the non-corrosion of the carbon steel serving as a substrate for the deposit. The deposit is impermeable to the electrolyte.

Example 14

The deposits were tested under conditions of wear by abrasive erosion identical to that occurring on the materials of hydraulic machines operating in an aqueous medium loaded with fine particles of solid material such as quartz.

• Ecoulement tangentiel et aussi avec un angle d'incidence liquide-pièce < 45
• Vitesse d'écoulement ≧ 48 m/s.
• Concentration en quartz de granulométrie = 200 µ de 20 g/l.

Comparative tests were made with other materials under the following conditions:

• Tangential flow and also with a liquid-part angle of incidence <45
• Flow velocity ≧ 48 m / s.
• Concentration of quartz with grain size = 200 µ of 20 g / l.

The wear measured at room temperature for deposition is equivalent to ceramic wear such as, for example, Cr₂O₃ and is significantly lower than metal alloys such as stellite, stainless steels such as dupleix or martensito-ferritic, as well as commercial steels known as resistant to abrasion.

Dry abrasive erosion tests at angles of incidence ranging from 0 to 90 ° give better behavior of the amorphous alloys according to the invention compared to ceramics and other metal alloys.

Examination of the structure by X-ray diffraction shows that the deposit has retained an amorphous structure similar to that at the start.

Finally, excellent results are also obtained when the deposits are applied to non-metallic substrates: wood, paper, synthetic substrates.

Claims (14)

1. Amorphous metallic coatings resistant to wear and corrosion, characterized in that they essentially consist of metallic alloys of general formula: $${\text{T}}_{\text{at}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

in which a + b + c + d + e + f + g + h = 100% in number of atoms
T is Ni, Co, or any choice of more than one of these elements associated with Fe, with: 3 <Fe <82 at and 3 <a <85% at.
M is one or more addition elements taken from the list: Mn, Cu, V, Ti, Mo, Ru, Hf, Ta, W, Nb, Rh with:     0 <e <12% at.
M ' is one or more rare earths, Yr included, with: 0 <f <4% at.
X is one or more metalloids chosen from C, P, Ge and Si with: 0 <g <17% at.,
I represents the inevitable processing impurities with: h <1% at. and:
5 ≦ b ≦ 25
5 ≦ c ≦ 15
5 ≦ d <18 2. Amorphous metal coatings resistant to wear and corrosion according to claim 1, characterized in that the metal alloys have the general formula: $${\text{Or}}_{\text{at}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

in which a + b + c + d + e + f + g + h = 100% in number of atoms.
M , M ' , X , I representing the same elements as those mentioned for formula (I), the compositions being those indicated above. 3. Amorphous metal coatings resistant to wear and corrosion according to claim 1, characterized in that the metal alloys have the general formula: $${\text{Or}}_{\text{at}}{\text{Fe}}_{\text{at'}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}\text{I}{}_{\text{h}}$$

    in which 0 ≦ a + a '≦ 85 at%
the other symbols having the same meaning as in formula (I). 4 - Amorphous metallic coatings resistant to wear and corrosion according to claim 1, characterized in that the metal alloys have the general formula: $${\text{Or}}_{\text{at}}{\text{Co}}_{\text{at''}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}{\text{I}}_{\text{h}}$$

in which 0 ≦ a + a '' ≦ 85 at%, the other symbols having the same meaning as in formula (I). 5 - Amorphous metallic coatings resistant to wear and corrosion according to claim 1, characterized in that the metal alloys have the general formula: $${\text{Or}}_{\text{at}}{\text{Fe}}_{\text{at'}}{\text{Co}}_{\text{at''}}{\text{Cr}}_{\text{b}}{\text{Zr}}_{\text{vs}}{\text{B}}_{\text{d}}{\text{M}}_{\text{e}}{\text{Me}}_{\text{f}}\text{X}{}_{\text{g}}{\text{I}}_{\text{h}}$$

with: 0 ≦ a + a '+ a''≦ 85 at%.
the other symbols having the same meaning as in formula (I). 6 - Process for obtaining wear-resistant and corrosion-resistant amorphous metal coatings according to claim 1, characterized in that said coatings are produced by depositing, on a substrate intended to receive them, powders of metallic alloy, obtained by atomization according to a particle size between 20 and 150 µm 7 - Process for obtaining wear-resistant and corrosion-resistant amorphous metallic coatings according to claim 6, characterized in that the powders are deposited by thermal spraying on metallic substrates with a thickness of between 0.03 and 1, 5 mm and preferably greater than 0.3 mm. 8 - Process for obtaining amorphous metallic coatings resistant to wear and corrosion according to claim 7, characterized in that the deposition of powders is carried out by the method of arc plasma blown under controlled atmosphere and temperature. 9 - Process for obtaining amorphous metallic coatings resistant to wear and corrosion according to claim 7, characterized in that the deposition of powders is carried out by the method of blown arc plasma, the path of the molten particles being protected from oxidation by an annular jet of nitrogen concentric with the plasma jet conveying the particles and of very slightly larger dimensions. 10 - Process for obtaining amorphous metallic coatings resistant to wear and corrosion according to one of claims 7 to claim 9, characterized in that the deposition of powders is followed by a cryogenic cooling step. 11 - Process for obtaining amorphous metallic coatings resistant to wear and corrosion according to claim 7 characterized in that a compacting step follows the deposition of material powders by thermal spraying on substrates. 12 - Process for obtaining wear-resistant and corrosion-resistant amorphous metal coatings according to claim 7 or claim 8, characterized in that the powders are deposited by thermal spraying on non-metallic substrates over a thickness of between 0 , 03 and 1.5 mm and preferably greater than 0.3 mm, this step being followed by a cryogenic cooling step. 13 - Process for obtaining amorphous metallic coatings resistant to wear and corrosion according to any one of claims 6 to 12, characterized in that the powders are deposited on surfaces which may be greater than 1 m². 14- Application of amorphous metallic coatings resistant to wear and corrosion obtained by implementing the method according to any one of claims 6 to 13 to the production of parts of hydraulic machines resistant to wear by scratching, by cavitation and abrasion erosion at temperatures below 400 ° C.

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