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.

Claims

1. An iron-based metallic glass alloy powder, represented by the following constituents: Fe.sub.(100-a-b-c-d)Cr.sub.aNi.sub.bMo.sub.c(B.sub.eC.sub.fSi.sub.g).sub.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: Fe.sub.26Cr.sub.24Ni.sub.14Mo.sub.8B.sub.12C.sub.10Si.sub.6.

5. The iron-based metallic glass alloy powder of claim 2, represented by the following constituents: Fe.sub.46Cr.sub.18Ni.sub.10Mo.sub.6B.sub.10C.sub.6Si.sub.4.

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.sub.(100-a-b-c-d)Cr.sub.aNi.sub.bMo.sub.c(B.sub.eC.sub.fSi.sub.g).sub.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.

Description

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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

[0038] 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.

[0039] 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.

[0040] The iron-based metallic glass alloy powder according to a preferred embodiment of the invention is represented by the following constituents:

[0041] Fe.sub.(100-a-b-c-d)Cr.sub.aNi.sub.bMo.sub.c(B.sub.eC.sub.fSi.sub.g).sub.d, where 18≤a≤24; 10≤b≤14; 6≤c≤8; 20≤d≤28; 10≤e≤12; 6≤f≤10; 4≤g≤6.

[0042] In an example, the iron-based metallic glass alloy powder according to the invention is represented by the following constituents: Fe.sub.26Cr.sub.24Ni.sub.14Mo.sub.8B.sub.12C.sub.10Si.sub.6.

[0043] In another example, the iron-based metallic glass alloy powder according to the invention is represented by the following constituents: Fe.sub.46Cr.sub.18Ni.sub.10Mo.sub.6B.sub.10C.sub.6Si.sub.4.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.sub.g), a crystalline temperature (T.sub.x), a crystallization peak temperature (T.sub.p), solidus temperature (T.sub.s), and a liquidus temperature (T.sub.l).

[0049] Some references have proposed that a reduced glass transition temperature T.sub.rg (=T.sub.g/T.sub.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.sub.x (=T.sub.x−T.sub.g) is also one of the indicators to determine the glass forming ability of the alloy. If the ΔT.sub.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.sub.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.sub.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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.sub.corr) and corrosion current density (I.sub.corr) relative to the specimens are determined, and are summarized in Table 1.

TABLE-US-00001 TABLE 1 specimen E.sub.corr (V) I.sub.corr (μA/cm.sup.2) AISI 316 S.S. −0.56 3.96 AISI 316 S.S. substrate with −0.56 4.7 amorphous coating

[0058] 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.

[0059] 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.sub.corr) and corrosion current density (I.sub.corr) relative to the specimens are determined, and are summarized in Table 2.

TABLE-US-00002 TABLE 2 specimen E.sub.corr (V) I.sub.corr (μA/cm.sup.2) AISI 316 S.S. −0.34 58.2 AISI 316 S.S. substrate with −0.29 39.2 amorphous coating

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.