IRON-BASED METALLIC GLASS ALLOY POWDER AND USE THEREOF IN COATING

Abstract

The invention provides an iron-based metallic glass alloy powder including: Fe as the main component; a metalloid element group including Si, B, and C; a small amount of Mo to improve the degree-of-supercooling; and the addition of Cr and Ni to increase corrosion resistance, where the total amount of the metalloid element group, the amount of the degree-of-supercooling improvement element and the total amount of the elements to increase corrosion resistance are set within predetermined ranges.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This utility application claims priority to Taiwan Application Serial Number 110138281, filed Oct. 15, 2021, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an iron-based metallic glass alloy powder and a thermal spray coating deposited by using an iron-based metallic glass alloy powder, and more in particular, to an iron-based metallic glass alloy powder with high hardness, high corrosion resistance and low manufacturing cost and a thermal spray coating deposited by using an iron-based metallic glass alloy powder.

For the relevant technical background of the invention, please refer to the references as follow.

• [1] U.S. patent publication no. 2005/0034792A1.
• [2] Shujie Pang, Tao Zhang, Katsuhiko Asami, and Akihisa Inoue, New Fe—Cr—Mo—(Nb,Ta)—C—B Glassy Alloys High Glass-Forming Ability and Good Corrosion Resistance, Materials Transactions, Vol. 42, No. 2 (2001), pp. 376-379.
• [3] Jun Shen, Qingjun Chen, Jianfei Sun, Hongbo Fan, and Gang Wang, Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy, Applied Physics Letters, 86 (2005), 151907.
• [4] S. P. Pang, T. Zhang, K. Asami, A. Inoue, Synthesis of Fe—Cr—Mo—C—B—P bulk metallic glasses with high corrosion resistance, Acta Materialia, 50 (2002), pp. 489-497.
• [5] U.S. patent publication no. 2016/0298216 A1.
• [6] U.S. patent publication no. 2019/0119797 A1.

2. Description of the Prior Art

Amorphous alloy is a new type of non-crystalline material that can be produced by modern rapid solidification processes and has much better mechanical, physical and chemical properties than conventional crystalline metals and alloys. Amorphous alloys are also called metallic glass or liquid metal. In contrast to conventional metals and alloys, those atoms are periodically arranged in a long-range order and consist of numerous grain boundaries, by contrast, the atomic arrangement of amorphous alloys is less order and irregular. Because of the irregular atomic arrangement and the lack of grain boundaries or precipitates in amorphous alloys, the uniform distribution of constituent elements in amorphous alloys makes it provide remarkable properties.

Amorphous alloys have some promising excellent physical, mechanical and chemical properties. For example, the strength, toughness, hardness, and modulus of amorphous alloys are superior to conventional metals and alloys. Amorphous alloys with specific compositions are excellent soft magnetic, catalytic, wear-resistant and corrosion-resistant materials.

Regarding the prior arts of amorphous alloys, many researches have confirmed that bulk amorphous alloys can be only obtained by carefully controlling their concentrations and compositions. A prior art discloses a bulk amorphous alloy with high glass forming ability can be achieved by adding a large difference in atomic size of constituent elements [1]. Another prior art discloses the typical iron-based bulk amorphous alloy of high glass forming ability is to be Fe₄₅Cr₁₆Mo₁₆C₁₈B₅ and the modification of such bulk amorphous alloy by the addition of Nb and Ta [2].

Another prior art discloses the addition of Co into Fe_48-xCo_xCr₁₅Mo₁₄C₁₅B₆Y₂ (x=0, 3, 5, 7, 9) can further increase the glass forming ability of the amorphous alloy [3]. However, it is well-known that adding Mo, Co, Y, Nb and Ta into the amorphous alloy will make such amorphous alloy much costly.

In addition, austenitic stainless steels, e.g., AISI 304 stainless steel or AISI 316 stainless steel, consist of 16-18 Cr (in wt. %) and 8-10 Ni (in wt. %). The formation of Cr and Ni oxide films on the surface of AISI 304 and 316 stainless steels protects these stainless steels from rusting and/or corrosion in certain environments. Conventional stainless steel powders with granular structure have been utilized as a coating material to modify the surface corrosion resistance of a structure or a component. However, the stainless steel coating is of low hardness (Vickers hardness (Hv) about 200) and low resistance to wear. As compared with conventional metallic coating with crystalline structure, iron-based amorphous alloy coating can provide superior properties, including high wear resistance and corrosion resistance. Another prior art discloses one composition of bulk iron-based amorphous alloy including Fe₄₃Cr₁₆Mo₁₆C₁₅B₁₀, which can be cast into a rod with a diameter of 2.5 mm by injecting the molten alloy into a copper mold under high cooling rate [4]. The prior art can be achieved by adding high Mo content to improve the glass forming ability of the iron-based amorphous alloy, however, it will make such iron-based amorphous alloy very expensive. Such a high price limits the usage of the iron-based amorphous alloy in the market.

In case of making amorphous alloy powders, the particle size of amorphous alloy powders usually is less than 300 μm. For typical thermal spray applications, the powder size of used amorphous alloy powders is usually less than 50 μm, and the thickness of deposited layer for one pass of thermal spray is generally less than 100 μm. To meet the actual requirement and not over design, the constituents of amorphous alloy powder can be modified to have low glass forming ability relative to that of bulk amorphous alloy. It is confirmed in this present invention that under proper alloy design, the Mo content of the iron-based metallic glass alloy can be greatly reduced but still can successfully produce amorphous alloy powder even by gas atomization.

However, many iron-based metallic glass alloys are poor in corrosion resistance relative to AISI 316 stainless steel, except ample elements that enhance the formation of stable passive film on the surface in corrosive environments are added. Even in conventional stainless steel, the presence of Cr in the stainless steel has an obviously positive influence on the corrosion resistance. To further increase the corrosion resistance at elevated temperature, it is wise to increase the Cr content of the iron-based metallic glass alloy powder. In addition, increasing the Cr content and extra addition of Ni improve the corrosion resistance of iron-based metallic glass alloy powder. The hardness of thermal spray coating by using iron-based metallic glass alloy powders can be higher than Hv 800, which is much harder than the austenitic stainless steel (Hv 200). The high hardness together with high corrosion resistance of the iron-based metallic glass coating is very useful in many applications. In addition, the iron-based metallic glass alloy powder can be used as the fine particle for shot-peening.

Regarding the prior art of iron-based metallic glass alloy powder, a prior art discloses an iron-based metallic glass alloy powder whose composition is (Fe_1-s-tCo_sNi_t)_100-x-y{(Si_aB_b)_m(P_cC_d)_n}_xM_y), and the compositional ratios of the iron-based metal element group Fe, Co, and Ni are such that 19≤x≤22, 0≤y≤6.0, 0≤s≤0.35 0≤t≤0.35 and s+t≤0.35 [5]. The prior art discloses the composition of the iron-based metallic glass alloy powder including predominant Fe and a group of metalloid elements that consists of Si, B, P and C, and a little amount of Nb and Mo to improve the degree of supercooling. As revealed in the iron-based metallic glass alloy powder disclosed by the prior art, the compositional ratio of M (M: either or both Nb and Mo) falls from 0.05 to 2.4 to improve the degree of supercooling, the compositional ratio of Co is less than 25.2 (atomic %), the compositional ratio of Ni is less than 25.2 (atomic %), and Co+Ni≤25.2 (atomic %). The iron-based metallic glass alloy powder disclosed by the prior art characterized with low eddy-current loss for an electronic component is 0.5-50 μm in particle size and produced by a water atomization process.

Another prior art discloses an iron-based metallic glass alloy powder whose composition is (Fe_1-s-tCo_sNi_t)_100-x-y{(Si_aB_b)_m(P_cC_d)_n}_xM_y), and the compositional ratios of the iron-based metal element group Fe, Co, and Ni are such that 19≤x≤22, 0≤y≤6.0, 0≤s≤0.35 0≤t≤0.35 and s+t≤0.35 [6]. M can be Nb and/or Mo. The compositional ratio of the Nb and Mo is preferably as low as possible within a range where necessary magnetic properties can be obtained. When s+t>0.35, not only the increase in Co or Ni content results in increase in raw material costs, but also the degree of supercooling decreases to an unmeasurable level [6]. The iron-based metallic glass alloy powder disclosed by the prior art has a particle size of 30 μm or less and is produced by a water atomization process. The disclosed iron-based metallic glass alloy powder is used as a material for powder compaction of various electronic components or as a material for coating materials for forming magnetic films on electronic circuit boards. The use of fine particle for electronic components is to reduce the eddy-current loss. It is emphasized that the cooling rate of the water atomization process is much higher than that of the gas atomization.

By reviewing the prior arts of metallic glass alloys, it can be clearly understood that there is still space for the improvement in the constituents of iron-based metallic glass alloy powders with high hardness, high corrosion resistance and low manufacturing cost.

SUMMARY OF THE INVENTION

Accordingly, one scope of the invention is to provide an iron-based metallic glass alloy powder with the advantages of high glass forming ability, low manufacturing cost, etc., and its application for thermal spray coating. Moreover, when the iron-based metallic glass alloy powder according to the invention is used to form a coating on a surface of a structure or a component, the coating has the advantages of high hardness, high corrosion resistance and the like.

An iron-based metallic glass alloy powder according to a preferred embodiment of the invention is represented by the following compositional formula: Fe_{(100-a-b-c-d)}Cr_aNi_bMo_c(B_eC_fSi_g)_d, where 18≤a≤24; 10≤b≤14; 6≤c≤8; 20≤d≤28; 10≤e≤12; 6≤f≤10; 4≤g≤6.

In one embodiment, the iron-based metallic glass alloy powder, according to the preferred embodiment of the invention, can be formed by a gas atomization process or a water atomization process.

In one embodiment, the iron-based metallic glass alloy powder, according to the preferred embodiment of the invention, has a particle size ranging from 5 μm to 300 μm.

A coating according to a preferred embodiment of the invention is produced by using the iron-based metallic glass alloy powder according to the invention.

In one embodiment, the coating according to the preferred embodiment of the invention is formed by a high velocity flame spray process.

Different from the prior arts, the iron-based metallic glass alloy powder according to the invention has the advantages of high glass forming ability, low manufacturing cost, etc., and can be successfully manufactured by a gas atomization process. Moreover, when the iron-based metallic glass alloy powder according to the invention is used to produce a coating on a surface of a structure or a component, the coating has the advantages of high hardness, high corrosion resistance, and the like.

The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1 shows a scanning electron microscopy (SEM) image of an iron-based metallic glass alloy powders manufactured by a gas atomization process according to the invention.

FIG. 2 shows the X-ray diffraction (XRD) spectra of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention.

FIG. 3 shows an SEM image of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention after a hardness test.

FIG. 4 shows a graph of the iron-based metallic glass alloy powder according to the invention measured by a differential scanning calorimetry (DSC) test.

FIG. 5 shows an SEM micrograph of the top surface morphology of an amorphous coating formed on an AISI 316 stainless steel substrate by a thermal spray process using the iron-based metallic glass alloy powder according to the invention.

FIG. 6 shows an SEM micrograph of a cross-section of the amorphous coating formed on an AISI 316 stainless steel substrate by a thermal spray process using the iron-based metallic glass alloy powder according to the invention.

FIG. 7 shows a graph of polarization curves of the specimens of an AISI 316 stainless steel and the amorphous coating according to the invention in a 3.5 wt. % NaCl aqueous solution.

FIG. 8 shows a graph of polarization curves of the specimens of the AISI 316 stainless steel and the amorphous coating according to the invention in a 0.5 M HCl aqueous solution.

FIG. 9 shows a photograph of the surface morphology of an AISI 316 stainless steel specimen after charging in gaseous HCl at 400° C. for 4 hours.

FIG. 10 shows the surface morphology of a specimen of an AISI 316 stainless steel substrate which an amorphous coating of the iron-based metallic glass alloy powder according to the invention is produced on and produced by a thermal spraying process after charging in gaseous HCl at 400° C. for 4 hours.

DETAILED DESCRIPTION OF THE INVENTION

Some preferred embodiments and practical applications of this present invention would be explained in the following paragraph, describing the characteristics, spirit, and advantages of the invention.

The invention relates to the constituent design of iron-based metallic glass alloy powder, in particular including: Fe as the predominant element; a group of metalloid elements that consists of Si, B and C; a little amount of glass forming (amorphization) element of Mo; and the addition of Cr and Ni to increase corrosion resistance. The atomic size of B, C and Si elements is smaller than that of Fe element; the atomic size of Cr and Ni elements is similar to that of Fe element; the atomic size of Mo element is larger than that of Fe element. In the constituent design of the iron-based metallic glass alloy powder according to the invention provides high glass forming ability, low manufacturing cost, high hardness, high corrosion resistance and other considerations.

The iron-based metallic glass alloy powder according to a preferred embodiment of the invention is represented by the following constituents:

Fe_{(100-a-b-c-d)}Cr_aNi_bMo_c(B_eC_fSi_g)_d, where 18≤a≤24; 10≤b≤14; 6≤c≤8; 20≤d≤28; 10≤e≤12; 6≤f≤10; 4≤g≤6.

In an example, the iron-based metallic glass alloy powder according to the invention is represented by the following constituents: Fe₂₆Cr₂₄Ni₁₄Mo₈B₁₂C₁₀Si₆.

In another example, the iron-based metallic glass alloy powder according to the invention is represented by the following constituents: Fe₄₆Cr₁₈Ni₁₀Mo₆B₁₀C₆Si₄.

In one embodiment, the iron-based metallic glass alloy powder, according to the preferred embodiment of the invention, can be produced by a gas atomization process or a water atomization process. It is emphasized that the cooling rate of the gas atomization process is much lower than that of the water atomization process.

Referring to FIG. 1, FIG. 1 is the SEM image of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention. As shown in FIG. 1, the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention exhibit spherical shapes.

Referring to FIG. 2, FIG. 2 is the XRD spectra of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention. As shown in FIG. 2, the XRD spectra of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention, shows a broad diffraction peaks only in the low-angle region (40°˜50°), and then disappears with the increase of the angle. This XRD spectra proves that the compositions of the iron-based metallic glass alloy powder according to the invention has high glass forming ability.

Referring to FIG. 3, FIG. 3 is an SEM image of the iron-based metallic glass alloy powders manufactured by the gas atomization process according to the invention after a hardness test. FIG. 3 shows the hardness indentation formed on the iron-based metallic glass alloy powder according to the invention after the hardness test. Regarding the hardness test, the iron-based metallic glass alloy powder manufactured by the gas atomization process according to the invention is embedded into a specimen, ground to provide a flat surface, and then measured the hardness of the iron-based metallic glass alloy powder by the micro-Vickers hardness tester under a load of 100 g. Tested by the micro-Vickers hardness tester, the hardness of the iron-based metallic glass alloy powder manufactured by the gas atomization process according to the invention is about Hv 1200. It is confirmed that the hardness of the iron-based metallic glass alloy powder manufactured by the gas atomization process according to the invention is equal to or greater than Hv 1200. The iron-based metallic glass alloy powder manufactured by the gas atomization process according to the invention has high hardness, which also means that the iron-based metallic glass alloy powder is manufactured by the gas atomization process according to the invention also has high wear resistance.

Referring to FIG. 4, FIG. 4 is a graph of the iron-based metallic glass alloy powders according to the invention measured by a DSC test. The DSC test is performed at a heating rate of 20° C./min. The characteristic temperatures measured by the DSC curve with continuous heating are also marked in FIG. 4. These characteristic temperatures include a glass transition temperature (T_g), a crystalline temperature (T_x), a crystallization peak temperature (T_p), solidus temperature (T_s), and a liquidus temperature (T_l).

Some references have proposed that a reduced glass transition temperature T_rg (=T_g/T_l) is an important indicator of glass forming ability of the alloy. The higher the reduced glass transition temperature, the stronger the glass forming ability of the alloy. Another references have proposed that ΔT_x (=T_x−T_g) is also one of the indicators to determine the glass forming ability of the alloy. If the ΔT_x value of the alloy is larger, the critical cooling rate required for amorphization of the alloy is also smaller, and the alloy is easier to form amorphous powder. As shown in FIG. 4, the reduced glass transition temperature of the iron-based metallic glass alloy powder according to the invention is 0.475, and the ΔT_x value of the iron-based metallic glass alloy powder according to the invention is 46° C. In the field of iron-based metallic glass alloy powder, the reduced glass transition temperature and ΔT_x of the iron-based metallic glass alloy powder according to the invention both are quite high, which proves that the iron-based metallic glass alloy powder according to the invention has high glass forming ability. The iron-based metallic glass alloy powder according to the invention can be produced successfully to be amorphous powder by a gas atomization process, which also reflects that the iron-based metallic glass alloy powder according to the invention has high glass forming ability. In addition, it is noted that the iron-based metallic glass alloy powder according to the invention can more easily manufacture into a coarse size amorphous powder by a water atomization process, and the manufacturing cost of the iron-based metallic glass alloy manufactured by the water atomization process powder according to the invention is lower.

In one embodiment, the iron-based metallic glass alloy powder according to the invention has a particle size ranging from 5 μm to 300 μm.

In practical application, the iron-based metallic glass alloy powder according to the invention has high hardness and high corrosion resistance, and can be used as a raw material for thermal spray coating and powder metallurgy. In addition, the spherical amorphous alloy powder is produced by the gas atomization process according to the invention can be used as a bead required for shot-peening.

A coating according to a preferred embodiment of the invention is formed of the iron-based metallic glass alloy powder according to the invention. The coating according to the invention is amorphous. When the iron-based metallic glass alloy powder according to the invention is used to form a coating on a surface of a structure or a component, the coating has the advantages of high hardness, high corrosion resistance and the like.

In one embodiment, the coating according to the invention can be formed by a high velocity flame spray process, but the invention is not limited to this.

Referring to FIG. 5, FIG. 5 is an SEM micrograph of the top surface morphology of an amorphous coating deposited on an AISI 316 stainless steel substrate by a thermal spray process using the iron-based metallic glass alloy powder according to the invention. As shown in FIG. 5, the amorphous coating deposited by using the iron-based metallic glass alloy powder according to the invention is a dense coating, which can effectively protect the substrate.

Referring to FIG. 6, FIG. 6 is an SEM micrograph in a cross-sectional view of the amorphous coating deposited on an AISI 316 stainless steel substrate by a thermal spray process using the iron-based metallic glass alloy powder according to the invention.

With a micro-Vickers hardness tester under a load of 50 g, FIG. 6 shows the hardness indentations formed on the amorphous coating after the hardness test and the hardness values corresponding to the hardness indentations are indicated. As shown in FIG. 6, the hardness value of the coating is above Hv 1100, which is close to the hardness of the raw iron-based metallic glass alloy powder according to the invention, while the hardness value of the AISI 316 stainless steel substrate is Hv 184. The mentioned-above hardness values confirms that the hardness of the amorphous coating deposited by using the iron-based metallic glass alloy powder according to the present invention is equal to or greater than Hv 1100.

In order to simulate the corrosive environment of seawater, the invention uses 3.5 wt % NaCl aqueous solution as the test solution. The specimens of an AISI 316 stainless steel and another AISI 316 stainless steel substrate with an amorphous coating deposited by using the iron-based metallic glass alloy powder according to the invention and by a thermal spraying process are prepared. These specimens are subjected to a polarization test in the 3.5 wt. % NaCl aqueous solution to evaluate the corrosion resistance of these specimens. The polarization curves of the specimens are shown in FIG. 7. By the polarization curves in FIG. 7, the important corrosion kinetic parameters such as corrosion potential (E_corr) and corrosion current density (I_corr) relative to the specimens are determined, and are summarized in Table 1.

	TABLE 1
	specimen	Ecorr (V)	Icorr (μA/cm2)
	AISI 316 S.S.	−0.56	3.96
	AISI 316 S.S. substrate with	−0.56	4.7
	amorphous coating

From the results listed in Table 1, it can be found that the corrosion potential of the amorphous coating is approximately identical to as that of AISI 316 stainless steel, but the corrosion current density of the amorphous coating is slightly higher than that of AISI 316 stainless steel. As shown in FIG. 6, even if there are micro-size defects present in the coating, for example, micro holes and the interface between the stacked layers, the amorphous coating according to the invention still has high corrosion resistance. It is believed that reducing the micro-defects in the amorphous coating according to the invention can further improve the corrosion resistance of the amorphous coating according to the invention.

The invention also uses 0.5 M HCl aqueous solution as another test solution. The specimens of an AISI 316 stainless steel and another AISI 316 stainless steel substrate with an amorphous coating deposited by using the iron-based metallic glass alloy powder according to the invention and by a thermal spraying process also are prepared. These specimens are subjected to a polarization curve test in the 0.5 M HCl aqueous solution to evaluate the corrosion resistance of these specimens. The polarization curves of the specimens are shown in FIG. 8. By the polarization curves in FIG. 8, the important corrosion kinetic parameters such as corrosion potential (E_corr) and corrosion current density (I_corr) relative to the specimens are determined, and are summarized in Table 2.

	TABLE 2
	specimen	Ecorr (V)	Icorr (μA/cm2)
	AISI 316 S.S.	−0.34	58.2
	AISI 316 S.S. substrate with	−0.29	39.2
	amorphous coating

From the results listed in Table 2, it can be found that the corrosion potential of the amorphous coating is a little negative than that of AISI 316 stainless steel, but the corrosion current density of the amorphous coating is much lower than that of AISI 316 stainless steel; the low current density means the good corrosion resistance of the material.

The results of FIG. 7, FIG. 8, Table 1 and Table 2 confirm that the amorphous coating deposited by using the iron-based metallic glass alloy powder according to the invention has excellent corrosion resistance.

Referring to FIG. 9 and FIG. 10, FIG. 9 is a photograph of the surface morphology of an AISI 316 stainless steel specimen after charging in gaseous HCl at 400° C. for 4 hours. FIG. 10 shows the surface morphology of a specimen of an AISI 316 stainless steel substrate on which an amorphous coating of the iron-based metallic glass alloy powder according to the invention is produced and deposited by a thermal spray process after charging in gaseous HCl at 400° C. for 4 hours.

As shown in FIG. 9 and FIG. 10, it was observed that brittle CrCl3.6H2O was formed in a large area on the AISI 316 stainless steel test piece. The spalling of CrCl3.6H2O shows the fact that the AISI 316 stainless steel has low resistance to chloride attack. By contrast, the test piece with an amorphous coating still show no cracking and spalling off the material. This means that at high temperatures, the AISI 316 stainless steel test piece has much lower resistance to chloride attack than the amorphous coating according to the present invention. The amorphous coating according to the present invention exhibits good resistance to gaseous chloride corrosion at 400° C.

With the detailed description of the above preferred embodiments, it is believed that the iron-based metallic glass alloy powder according to the invention has the advantages of high glass forming ability, low manufacturing cost, etc., which can be successfully made by a gas atomization process. If the iron-based metallic glass alloy powder according to the invention is manufactured by a water atomization process, a larger size of iron-based metallic glass alloy powder can be produced, and the manufacturing cost of the iron-based metallic glass alloy powder can be lowered. In addition, when the iron-based metallic glass alloy powder according to the invention is used to form a coating on a surface of a structure or a component, the coating has the advantages of high hardness, high corrosion resistance, etc., and even has good resistance to gaseous chloride erosion at high temperatures.

With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

1. An iron-based metallic glass alloy powder, represented by the following constituents: Fe(100-a-b-c-d)CraNibMoc(BeCfSig)d,wherein 18≤a≤24; 10≤b≤14; 6≤c≤8; 20≤d≤28; 10≤e≤12; 6≤f≤10; 4≤g≤6.

2. The iron-based metallic glass alloy powder of claim 1, being produced by a gas atomization process or a water atomization process.

3. The iron-based metallic glass alloy powder of claim 2, having a particle size ranging from 5 μm to 300 μm.

4. The iron-based metallic glass alloy powder of claim 2, represented by the following constituents: Fe26Cr24Ni14Mo8B12C10Si6.

5. The iron-based metallic glass alloy powder of claim 2, represented by the following constituents: Fe46Cr18Ni10Mo6B10C6Si4.

6. The iron-based metallic glass alloy powder of claim 2, having a hardness equal to or greater than Hv 1200.

7. A coating being formed of an iron-based metallic glass alloy powder, the iron-based metallic glass alloy powder being represented by the following constituents comprising: Fe(100-a-b-c-d)CraNibMoc(BeCfSig)d,wherein 18≤a≤24; 10≤b≤14; 6≤c≤8; 20≤d≤28; 10≤e≤12; 6≤f≤10; 4≤g≤6.

8. The coating of claim 7, being formed by a high velocity flame spray process.

9. The coating of claim 8, having a hardness equal to or greater than Hv 1100.