Bulk metallic glass alloys containing nickel (NI) - cobalt (CO) - molybdenum (MO) - boron (b)

Abstract

The invention is related to nickel-based metallic glass alloys that can be produced in an amorphous structure, that contain metals with a high melting point and a high boron content, and that, when subjected to heat treatments above their crystallization temperatures, both a phase with high fracture toughness (nickel solid solution) and borides with high hardness values can be precipitated.

Description

[0001] BULK METALLIC GLASS ALLOYS CONTAINING NICKEL (Ni) - COBALT (Co) - MOLYBDENUM (Mo) - BORON (B)

[0002] TECHNICAL FIELD

[0003] The invention relates to nickel-based metallic glass alloys that can be produced in an amorphous structure, that contain metals with a high melting point and a high boron content, and that, when subjected to heat treatments above their crystallization temperatures, both a phase with high fracture toughness (nickel solid solution) and borides with high hardness values can be precipitated.

[0004] PRIOR ART

[0005] Metallic glass alloys are a group of materials with extremely unique physical and chemical properties. Due to these attractive properties, intensive studies have been carried out on metallic glass alloys for the last 40 years. As a result of these studies, many metallic glass alloys (such as Fe-based, Co-based, Ni-based, Cu-based, Zr- based) have been developed. In addition, studies on the crystallization behavior of metallic glass alloys in recent years have shown that metallic glass alloys can also be used as precursors in the production of metal matrix composites. Metal matrix composites are traditionally obtained by sintering high hardness phase or phases such as carbide, boride, nitride, and oxide together with a metal matrix (such as nickel, cobalt, iron, copper, and aluminum) with high fracture toughness. Sintering processes are carried out by various methods such as hot pressing (HP), hot isostatic pressing (HIP), and spark plasma sintering (SPS). There are many advantages to producing metal matrix composites by crystallization of metallic glasses instead of these traditional methods. The most important of these advantages is that composite parts with a section thickness smaller than the critical casting thickness of the precursor metallic glass alloy (the largest section thickness at which the alloy can be obtained in a completely glassy structure) can be produced in the desired geometry by melting, casting and subsequent heat treatment. This is a very important advantage in terms of obtaining parts with complex geometry that are difficult to produce with traditional sintering methods. In addition, there will be no pore formation in the structure as a result of the production of composite parts by melting, casting, and heat treatment methods. As is known, the pores that may occur in the case of production by sintering are a factor that negatively affects the fracture toughness of the material. In addition, the distribution of phases in the structure of composite materials produced by melting, casting, and heat treatment processes will be homogeneous. In order to ensure the homogeneity of these phases in sintering methods, the components forming the composite must be mixed in high-speed mills for long periods (~24 hours) before the sintering process. The production of some parts can be difficult by melting and casting due to their complex shapes. In this case, the targeted product can first be produced in a simple geometry by melting and casting and then brought to the desired shape by thermoplastic shaping. Then, a product with a composite structure can be obtained by heat treatment of the shaped part.

[0006] In order for composite materials obtained by crystallization of metallic glass alloys to have both high hardness and high fracture toughness, at least one of the phases formed (precipitated) in the structure during heat treatment must have high hardness and at least one must have high fracture toughness. There are studies in the literature showing that composites containing boride and / or carbide type phases with high hardness in the structure can be produced by crystallizing metallic glass alloys containing high amounts of boron and / or carbon through heat treatment. Very high hardness values (~1800 Hv) were obtained in composites produced by heat treating bulk metallic glass alloys, generally based on Iron (Fe), Cobalt (Co), and Iron-Cobalt (Fe-Co) and containing high amounts of boron and / or carbon, at temperatures above their crystallization temperatures. The high hardness values of these composites are due to the carbide and boride type phases such as (Fe, Cr)?C3, (Fe, Ni, Mo)23Be, (Fe, Cr)23(C, B)e, (CO, Fe)2B (Co, Fe)23Ta2Be and CoWB that precipitate in the structure during heat treatment. Among these composites, the presence of a phase that would provide high fracture toughness has not been reported in any of them except the composite produced by crystallization of Ni-Co-W-B bulk metallic glass alloys, which has both nickel solid solution and CoWB phase precipitated in its structure. Therefore, fracture toughness values of composites other than the composite produced by crystallization of Ni-Co-W-B bulk metallic glass alloys were not reported. BRIEF DESCRIPTION OF THE INVENTION

[0007] The invention relates to nickel-based bulk metallic glass alloys containing more than 12% (atomic) boron. When nickel-based bulk metallic glass alloys with amorphous structure, as described in the invention, are subjected to heat treatment at temperatures above their crystallization temperatures, both nickel solid solution with face-centered cubic (FCC) structure and borides precipitate in their microstructures. In the resulting nickel matrix composite, the nickel solid solution provides high fracture toughness, while the precipitated borides provide high hardness. Thus, it can be turned into a composite with improved toughness and hardness properties.

[0008] List of Figures

[0009] Figure 1. X-ray diffraction (XRD) patterns of samples of Ni-Co-Ta-B alloys with a section thickness of 0.3 mm

[0010] Figure 2. X-ray diffraction (XRD) patterns of Ni-Co-Nb-B alloys with 0.3 mm section thickness.

[0011] Figure 3. X-ray diffraction (XRD) patterns of samples of Ni-Co-V-B alloys with a section thickness of 0.3 mm

[0012] Figure 4. X-ray diffraction (XRD) patterns of samples of Ni-Co-Mo-B alloys with a section thickness of 0.3 mm

[0013] Figure 5. X-ray diffraction (XRD) patterns of samples with critical casting thickness (Dcriticai) of some of the developed nickel-based bulk metallic glass alloys.

[0014] Figure 6. Graphical view of DSC analysis (heating) results of alloys with XRD analysis results given.

[0015] Figure 7. Graphical view of DSC analysis (cooling) results of alloys with XRD analysis results given.

[0016] Figure 8. X-ray diffraction (XRD) patterns of composite samples obtained as a result of heat treatments applied to Ni33Co3oMoieW2Nb4Bi5 metallic glass alloy at 677 °C for 25 to 200 min.

[0017] Figure 9. Graphical view of the change in microhardness values of composite samples obtained as a result of heat treatments applied to Ni33Co3oMoieW2Nb4Bi5 metallic glass alloy at 677 °C for 25 to 200 min. depending on the heat treatment time.

[0018] Figure 10. XRD pattern of a sample of Ni4iCo22Mo22Bi5 alloy with a section thickness of 2 mm. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order for composite materials obtained by crystallization of metallic glasses to have high fracture toughness, phase or phases with face-centered cubic (FCC) structure must be formed in the structure of the composite during heat treatment. In order to form a phase or phases with a face-centered cubic structure in the structure as a result of heat treatment, the metallic glass alloy system must be copper or nickel based. Copper-based bulk metallic glass alloys (metallic glasses with a section thickness greater than 0.3 mm (millimeters) that can be obtained in a completely amorphous structure) containing high amounts (> 12 atomic %) of boron and / or carbon have not been reported in the literature within the known technique. Only one nickel- based bulk metallic glass alloy system containing high amounts (>12 atomic %) of boron and / or carbon has been reported [TR 2019 04074 B, CN 113825855 B, US 12,098,451 B2 ]. The main elements that constitute this nickel-based alloy system are nickel, cobalt, tungsten, and boron. As a result of the crystallization of the Ni-Co-W-B metallic glass alloys by heat treatments at temperatures above their crystallization temperatures, both a phase with high fracture toughness (nickel solid solution with face-centered cubic (FCC) structure) and borides with high hardness (especially CoWB phase) precipitate in the structure. The composites obtained have high hardness and fracture toughness values. However, since the metallic glass alloy system in question contains a high amount of tungsten, the densities of the alloys and the composites obtained through heat treatment range from approximately 11 -13 gr / cm3. These density values are higher than the densities of conventional metallic alloys (carbon steel ~7.8 gr / cm3, stainless steels ~7.5-8 gr / cm3, nickel alloys ~7.8-9 gr / cm3, copper alloys ~8.7-8.9 gr / cm3). These high density values are undesirable in applications where low density is a key factor (such as in aerospace, space, and automotive applications) that require high strength-to-weight ratios. Additionally, since the Ni-Co-W-B metallic glass alloys contain a high amount of tungsten, which has a very high melting point (3422°C), the production of these alloys using melting methods other than vacuum arc melting becomes difficult and, in some cases, even impossible. Therefore, the alloys must first be melted using vacuum arc melting (pre-alloying) and then remelted using a suitable method for the target application (mostly induction melting) to produce the final product in the desired form (rod, strip, powder). In other words, in most cases, the production processes of the alloys must be carried out in two stages. This complicates, lengthens, and increases the cost of the production process. Therefore, there is a need to develop new, cost-effective alloys with lower melting points, which would allow for a single-step production process, as a replacement for these alloys with high melting points. Advanced materials that meet these needs will not only simplify production but also provide various economic savings during use (such as production cost, product cost, fuel, and energy savings).

[0020] The use of other refractory elements (such as Ta, Nb, V, or Mo) instead of tungsten in the Ni-Co-W-B metallic glass alloy system may enable the production of precursor metallic glass alloys that facilitate production (single-step production) due to their lower melting points, and, at the same time, allow for the creation of composites with similar mechanical properties (high microhardness and high fracture toughness) and lower density, composed of a nickel solid solution with a face-centered cubic (FCC) structure and borides, obtained by crystallizing at temperatures above the crystallization temperatures of Ni-Co-W-B metallic glass alloys. However, as a result of experimental studies conducted by the inventors, it has been found that only the element molybdenum can be used instead of tungsten. Figures 1 , 2, 3, and 4 show the X-ray diffraction (XRD) analysis results of samples of the alloys produced by the copper mold suction casting method with a section thickness of 0.3 mm, using tantalum, niobium, vanadium, and molybdenum, respectively, as substitutes for tungsten. It is observed that the samples of the alloys produced by using tantalum, niobium, and vanadium instead of tungsten do not contain an amorphous structure and consist entirely of crystalline phases. Since these alloys are already made up entirely of crystalline phases, it is not possible to produce composites by applying a heat treatment to the cast samples of the alloys for crystallization. In other words, these alloys cannot be used as precursors for composite production. The results obtained by the inventors have shown that bulk metallic glass alloys with completely amorphous structure can be obtained by using only molybdenum element instead of tungsten. These alloys, which have a completely amorphous structure, are suitable to be used as precursors for composite production through heat treatment.

[0021] The nominal composition description used in defining the nickel-based bulk metallic glass alloy which is the subject of the invention is given below:

[0022] NiaCobMocBdMIeM2fM3gM4h defines M1 : At least one of Fe (iron), Cu (copper), Cr (chromium), Mn (manganese), Al (aluminum), and Sn (tin) elements.

[0023] M2: At least one of Ti (titanium), Zr (zirconium), Er (erbium), Sm (samarium), Nd (neodymium), Y (yttrium), La (lanthanum), and Hf (hafnium) elements.

[0024] M3: At least one of W (tungsten), Ta (tantalum), Nb (niobium), and V (vanadium) elements.

[0025] M4: At least one of C (carbon), Si (silicon), P (phosphorus), and Be (beryllium) elements.

[0026] The amounts of the components, a, b, c, d, e, f, g, and h are indicated on the atomic % basis.

[0027] Here, a: 10-65, b: 2-40, c: 5-40, d: 12.1 -35, e: 0-40, f: 0-15, g: 0-20, h: 0-20 a+b+e+f: changes between 20-75 c+g: changes between 5-40 d+h: changes between 12.1-35.

[0028] The compositions, critical casting thicknesses, and thermal properties (glass transition temperature, crystallization temperature, and liquidus temperature) of some of the Ni-Co-Mo-B bulk metallic glass alloys which are the subject of the invention are given in Table 1 as examples. In addition, the density values of some of the Ni-Co-Mo- B bulk metallic glass alloys, which are the subject of the invention, and the density values of the Ni-Co-W-B bulk metallic glass alloys, which are the invention previously disclosed in the patent document numbered TR2019 / 04074 belonging to the inventors, are given in Table 2. The obtained data show that when comparing Ni-Co-Mo-B and Ni-Co-W-B bulk metallic glass alloys with the same Ni, Co, and B content, the densities of Ni-Co-Mo-B bulk metallic glass alloys are significantly lower.

[0029] The new alloys which are the subject of the invention were produced by the arc melting method and the casting process was carried out by using the suction casting method in an arc melting furnace. Critical casting thicknesses of alloys were determined by using high purity copper (electrolytic copper) casting molds with different section thicknesses. Structural analyses of the produced samples were made by X-ray diffraction (XRD) method. According to XRD analysis results, the largest section thickness that an alloy can be obtained in a completely amorphous structure was accepted as the critical casting thickness of that alloy. The glass transition temperature (Tg) and crystallization temperature (Tx) values of nickel-based bulk metallic glass alloys given in Table 1 were determined by differential thermal calorimeter (DSC). The heating rate used during the analysis was 20 °C / min. The liquidus temperature (Ti) values of nickel-based bulk metallic glass alloys given in Table 1 were also determined by DSC analysis. For this purpose, the samples were first heated to 1500 °C in the DSC device and completely melted. Then, the completely melted samples were cooled with a cooling rate of 20 °C / min, and the Ti values were determined.

[0030] Table 1. Critical casting thicknesses (Dcriticai), glass transition (Tg), crystallization (Tx), and liquidus (Ti) temperatures of some of the developed nickel-based bulk metallic glass alloys.

[0031] Table 2. Density values of Ni-Co-Mo-B and Ni-Co-W-B bulk metallic glass alloys.

[0032] The XRD analysis results of samples with critical casting thickness (Dcriticai) of some of the nickel-based bulk metallic glass alloys given in Table 1 are given in Figure 5. The DSC analysis results of the alloys whose XRD analysis results are given in Figure 5 are also given in Figures 6 and 7. The glass transition (Tg) and crystallization (Tx) temperatures of each alloy are shown in Figure 6 in the DSC analysis results obtained with a heating rate of 20 °C / min. The liquidus (Ti) temperatures of each alloy are shown in Figure 7 in the DSC analysis results obtained with a cooling rate of 20 °C / min after complete melting.

[0033] The nickel-based bulk metallic glass alloys shown in Table 1 are given as examples without limiting the scope of protection of the invention. The values in the table, when added together, provide examples of how the content of a 100 % alloy can be created. The basic components of the nickel-based bulk metallic glass alloys that constitute the invention are nickel (Ni), cobalt (Co), molybdenum (Mo), and boron (B) elements. These four elements must be present simultaneously in all alloys in the proportions specified above (%a, b, c, and d). In addition to these four main elements (Ni, Co, Mo, and B), it is not mandatory to include in the formulation the alloys developed by adding the elements named M1 , M2, M3, and M4 to the composition of the alloy in the specified proportions (e, f, g and h%, respectively).

[0034] The alloys were produced by vacuum arc melting with a protective gas environment. The alloy parts, which were completely liquid (molten), were obtained by rapid cooling via vacuum suction casting using electrolytic copper molds. In addition, thick section parts can be produced by different production casting methods (induction melting route with injection casting, bend casting, drop casting, etc.) with a protective gas atmosphere in the production of these alloys.

[0035] In addition, the developed nickel-based metallic glass alloys can also be produced in powder form. Various atomization methods (such as gas atomization, water atomization, and ultrasonic powder atomization) can be used for production in powder form, as well as the method of first producing it in thin ribbons by melt spinning and then grinding the ribbons. These produced metallic glass alloy powders are then sintered using various sintering methods (such as hot pressing (HP), hot isostatic pressing (HIP), and spark plasma sintering (SPS)) to obtain products with the desired size and geometry in a completely amorphous structure. In addition, it is also possible to obtain products with the desired size and geometry in a completely amorphous structure with the produced metallic glass alloy powders and the additive manufacturing methods that are currently being developed (such as selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), direct metal deposition (DMD). In addition, it is possible to obtain coatings with completely amorphous structure and having high hardness and wear resistance on weak materials by using various coating methods (such as high-speed oxygen-fuel (HVOF), plasma coating, cold spraying, laser coating) using the produced metallic glass powders.

[0036] Alloys with a critical casting thickness of less than 0.3 mm can also be produced in powder form. The production of these alloys in powder form can be done by atomization methods (such as gas atomization, water atomization, and ultrasonic powder atomization) or by first producing them in thin ribbons by melt spinning and then grinding the thin ribbons. Since the glass forming abilities of alloys vary depending on their composition, powders produced from some alloys may not be completely amorphous and the structure of the powders may contain some nickel solid solution and some boride phases along with the amorphous phase. It is possible to obtain bulk parts with the desired geometry and size, completely or largely amorphous structure (containing some nickel solid solution and borides in their structure) by sintering these metallic glass powders with a completely amorphous structure or a structure containing some nickel solid solution and borides in addition to the amorphous phase, using various sintering methods (such as HP, HIP, SPS). In addition, it is possible to obtain products with the desired size and geometry, completely or largely amorphous, with the additive manufacturing methods (such as SLS, SLM, EBM, and DMD) that are being developed today, using metallic glass powders that have a completely amorphous structure or a structure that also contains some nickel solid solution and borides in addition to the amorphous phase. In addition, it is possible to obtain coatings with high hardness and wear resistance, completely or largely amorphous, on weak materials by using various coating methods (such as high-velocity oxygen-fuel (HVOF), cold spraying, laser coating) using metallic glass powders that have a completely amorphous structure or a structure that contains some nickel solid solution and borides in addition to the amorphous phase.

[0037] The Ni-based alloys mentioned in our invention meet the need for the development of high strength alloys having the relationship of single-stage melting, low density, high hardness, and high fracture toughness and are an invention that cannot be derived from the known art in terms of their compositions. The basic components of the nickel-based bulk metallic glass alloys that constitute the invention are nickel (Ni), cobalt (Co), molybdenum (Mo), and boron (B) elements. The nickel-based bulk metallic glass alloys that are the subject of the invention were developed by the presence of these four elements in all alloys simultaneously in the above-mentioned proportions (%a, b, c, and d). In addition to these four main elements (Ni, Co, Mo, and B), the addition of elements named M1 , M2, M3, and M4 in the specified proportions (e, f, g, and h%, respectively) to the composition of the alloy further enhances the thermal properties (Tgand Tx) and critical casting thicknesses (Dcnticai) of the developed alloys to even higher levels. The biggest difference that distinguishes the nickel-based bu metallic glass alloys, which are the subject of the invention, from the nickel-based bulk metallic glass alloys in the known art is that they contain both a high content of molybdenum (5-40% atomic) and a high content of boron (12.1-35% atomic). In order for the composite material obtained to have both high hardness and high toughness, at least one of the phases formed (precipitated) in the structure during heat treatment must have high hardness and at least one must have high toughness. Thus, the precipitation of borides with high hardness (especially CoMoB) is achieved in a high volume fraction.

[0038] Nickel (Ni), Cobalt (Co), Molybdenum (Mo), and Boron (B), which are the alloy elements that make up the invention, are present in all alloys. Because, in order for the nickel solid solution with high toughness to precipitate in the structure of the composite materials to be obtained by heat treatment of the developed nickel-based bulk metallic glasses, the nickel element must be present in the composition of all alloys. In order for the borides (especially the CoMoB phase) to form, which will precipitate as a result of heat treatment and provide the composite with high hardness, the elements forming this phase (Co, Mo, and B) must be present in the composition of the alloys. The proportions of these elements in the alloys are within the specified ranges (%a, b, c, and d). The elements grouped as M1 , M2, M3, and M4 have been used to enhance both the glass forming ability and the thermal stability of the alloys. For example, the critical casting thickness of Ni33Co3oMo22Bi5 alloy containing only Ni, Co, Mo, and B elements is 0.3 mm, while the critical casting thickness of Ni33Co3oMoieNb4W2Bi5 alloy with 4% niobium (Nb) (M3) and 2% tungsten (W) (M3) addition is 0.5 mm. The Tgand Txtemperatures of Ni33Co3oMo22Bi5 metallic glass alloy were determined as 539 °C and 577 °C, respectively. The Tgand Tx temperatures of the NissCosoMo WeBis metallic glass alloy obtained as a result of the 6% tungsten (W) (M3) addition to the alloy were measured as 563 °C and 601 °C, respectively. The thermal stability of the alloy was increased as a result of the tungsten addition. The increase in thermal stability enables the alloy to be used in amorphous or composite structures without undergoing structural changes at higher temperatures. The nickel-based bulk metallic glass alloys subject to the invention contain both a high amount of nickel and molybdenum, as well as a high amount of boron. By heat treating the nickel-based bulk metallic glass alloys, which are the subject of our invention, at temperatures above the crystallization temperatures given in Table 1 , both a nickel solid solution with a face-centered cubic (FCC) structure providing high fracture toughness and containing some cobalt and molybdenum, and borides (especially CoMoB) providing high hardness are precipitated. Since the crystallization temperatures of nickel-based bulk metallic glass alloys used as precursors vary depending on the composition of the alloys, the heat treatment temperatures to be used are different for each metallic glass alloy. For example, the Ni33Co3oMo22Bi5 alloy needs to be heat treated at temperatures above 577 °C to form a nickel solid solution with a face-centered cubic (FCC) structure that provides high fracture toughness and contains some cobalt and molybdenum, and to precipitate borides that provide high hardness, while the Ni25Co3oMo3oBi5 alloy needs to be heat treated at temperatures above 640 °C.

[0039] Without limiting the scope of protection of our invention, as an example, the crystallization temperature of the Ni33Co3oMoieW2Nb4Bi5 metallic glass alloy is 607 °C. The XRD patterns of the composite samples obtained by heat treating completely amorphous samples of the Ni33Co3oMoieW2Nb4Bi5 alloy at 677 ° C for periods ranging from 25 to 200 min are given in Figure 8. When a completely amorphous sample of the alloy is subjected to heat treatment for 25 min, some nickel solid solution with a facecentered cubic (FCC) structure precipitates in the structure. There is also some amorphous phase in the structure. When the heat treatment time is increased to 50 min., the amount of nickel solid solution precipitated in the structure increases. However, there is still some amorphous phase in the structure. As a result of the heat treatment for 75 min., the amount of nickel solid solution precipitated in the structure increases. In addition, a very small amount of CoMoB phase also precipitates. In addition, there is a small amount of amorphous phase in the structure. When the heat treatment time is increased to 100 min., it is observed that a significant amount of CoMoB phase precipitates in addition to the nickel solid solution precipitated in the structure. It was also determined that a very small amount of NisMo phase precipitated in the structure. It was determined that the amounts of phases formed (precipitated) in the structure of the composite did not change as a result of heat treatments performed for periods longer than 100 min. In summary, as a result of heat treatment of the nickel-based bulk metallic glass alloys subject to the invention at low temperatures and short heat treatment times, only crystals of the nickel solid solution with the face-centered cubic (FCC) structure precipitate in the structure.

[0040] As a result, the structure consists of an amorphous phase and nickel solid solution. When the heat treatment temperature and / or heat treatment time are increased, the CoMoB phase precipitates in addition to the nickel solid solution. As a result, the structure consists of nickel solid solution and CoMoB phase.

[0041] The variation in microhardness values of the samples obtained by heat treating completely amorphous samples of Ni33Co3oMoieW2Nb4Bi5 alloy at 677 °C for times ranging from 25 to 200 min depending on the heat treatment time are given in Figure 9. The hardness values of the composite samples were determined by applying a 500 g (4.9 N) load for 15 seconds on the Vickers microhardness tester. The microhardness measurement results are the arithmetic average of 10 measurements made from different regions for each composite sample. The hardness of the sample with a completely amorphous structure of the alloy was determined as 1026 Hv. The microhardness value of the composite obtained as a result of heat treatment of the alloy's completely amorphous sample for 25 min. was measured as 1219 Hv. It was determined that the microhardness values of the composites obtained increased as a result of increasing the heat treatment time. A composite material with a microhardness value of 1260 HV was obtained due to the phases (nickel solid solution and CoMoB) precipitated in the structure as a result of heat treatment for 75 min.

[0042] The microhardness values of these composite materials, which are obtained by heat treatment of the Ni33Co3oMoieW2Nb4Bi5 metallic glass alloy, which is given as an example of the composite materials of the invention, vary depending on the volume fractions and average grain sizes of the nickel solid solution and CoMoB phases precipitated in the structure depending on the heat treatment temperature and heat treatment time. The fracture toughness of the composites subject to the invention also varies depending on the volume fractions and average grain sizes of the nickel solid solution and CoMoB phases precipitated in the structure depending on the heat treatment time and heat treatment temperature.

[0043] The metallic glass alloy powders with a completely amorphous structure, produced by atomization methods (such as gas atomization, water atomization, and ultrasonic powder atomization) or by initially producing fine strips via the melt spinning method followed by grinding the fine strips, are sintered or used in additive manufacturing to produce fully amorphous parts. When these parts are subjected to heat treatment at temperatures above the crystallization temperature of the metallic glass alloy used in production, a nickel solid solution with FCC structure and borides (especially the CoMoB phase) precipitate in the structure. As a result, the manufactured part is obtained in a composite structure. In addition, by subjecting the amorphous coatings obtained using metallic glass powders to heat treatment at temperatures above the crystallization temperature of the alloy used in the coating, nickel solid solution and borides (especially the CoMoB phase) with an FCC structure are precipitated. As a result, a composite coating with high hardness and fracture toughness is obtained.

[0044] The metallic glass alloy powders, which are not fully amorphous but contain a certain amount of crystalline phases (nickel solid solution and borides), produced by atomization methods (such as gas atomization, water atomization, and ultrasonic powder atomization) or by initially producing fine strips via the melt spinning method followed by grinding the fine strips, are sintered or used in additive manufacturing to produce parts with a partially amorphous structure. When these parts are subjected to heat treatment at temperatures above the crystallization temperature of the metallic glass alloy used in production, in addition to the phases already present in the structure, a nickel solid solution with FCC structure and borides (especially the CoMoB phase) precipitate. As a result, the manufactured part is obtained in a composite structure. In addition, as a result of the heat treatment of the partially amorphous coatings obtained using these metallic glass powders at temperatures above the crystallization temperature of the alloy used in the coating, in addition to the phases already present in the structure, nickel solid solution and borides (especially the CoMoB phase) with an FCC structure are precipitated. As a result, a composite coating with high hardness and fracture toughness is obtained.

[0045] The structure of the powders of some alloys with a critical casting thickness value lower than 0.3 mm, produced by atomization methods (such as gas atomization, water atomization, and ultrasonic powder atomization) or by first producing them in the form of thin strips by melt spinning method and then grinding the thin strips, may consist entirely of crystalline phases (nickel solid solution and borides). It is possible to obtain bulk parts with the desired geometry and size in a composite structure consisting of completely crystalline phases (nickel solid solution and borides) by sintering the alloy powders consisting of these completely crystalline phases with various sintering methods (such as HP, HIP, SPS). Since this approach does not involve a heat treatment process, it may be preferred in some applications from an energy efficiency perspective. Furthermore, it is also possible to produce composite materials with desired dimensions and geometries using these fully crystalline phase alloy powders through currently developing additive manufacturing methods (such as SLS, SLM, EBM, DMD, etc.). In addition, these alloy powders composed of fully crystalline phases can be used to obtain composite coatings made of fully crystalline phases (nickel solid solution and borides) with high hardness and wear resistance on weak materials through various coating methods (such as high-velocity oxygen-fuel (HVOF), cold spraying, laser coating, etc.). Since this approach does not involve a heat treatment process, it may be preferred in some applications from an energy efficiency perspective.

[0046] It is possible to produce parts with thicknesses above the critical casting thickness of the alloys subject to the invention in a composite structure by casting methods (injection casting with induction melting route, bend casting, drop casting, etc.). The structure of the part with a section thickness greater than the critical casting thickness of the alloy may consist of partly amorphous and partly crystalline phases (only nickel solid solution or nickel solid solution and borides) or completely crystalline phases (only nickel solid solution or nickel solid solution and borides), depending on the casting thickness. If the part contains a partially amorphous structure, the final composite structure can be obtained by heat treatment at a temperature above the crystallization temperature for an appropriate period of time. If the part produced consists entirely of crystalline phases, no heat treatment is required. The first of these approaches involves a partial heat treatment process and the second does not involve any heat treatment process, so it can be preferred in terms of energy efficiency in some applications.

[0047] Without limiting the scope of protection of our invention, as an example, the critical casting thickness of the Ni4iCo22Mo22Bi5 metallic glass alloy is 0.3 mm. The XRD pattern of the sample of the Ni4iCo22Mo22Bi5 alloy produced with a 2 mm section thickness by the suction casting method in a copper mold is given in Figure 10. It is seen that the structure of the sample contains only the nickel solid solution and the CoMoB phase. Since the obtained sample already has a composite structure after casting, no heat treatment is required.

[0048] The nickel-based bulk metallic glass alloys, which are the subject of our invention, are nickel-based bulk metallic glass alloys in which both a phase with high fracture toughness (nickel solid solution) and borides with high hardness (primarily CoMoB phase) can be formed in the structure as a result of heat treatment at temperatures above their crystallization temperatures. The CoMoB phase, which has an orthorhombic structure, has a space group of Pnma and lattice parameters of a = 5.803 A, b = 3.253 A, and c = 6.677 A.

Claims

CLAIMS1. A nickel-based bulk metallic glass alloy containing high amount of refractory metal and boron characterized by NiaCobMocBdM1eM2fM3gM4h formula.

2. The M1 of Claim 1 , characterized by being at least one of the Fe, Cu, Cr, Mn, Al, and Sn elements.

3. The M2 of Claim 1 , characterized by being at least one of the Ti, Zr, Er, Sm, Nd, Y, La, and Hf elements.

4. The M3 of Claim 1 , characterized by being at least one of the W, Ta, Nb, and V elements.

5. The M4 of Claim 1 , characterized by being at least one of the C, Si, P, and Be elements.

6. The nickel-based bulk metallic glass alloy containing high amount of refractory metal and boron of Claim 1 , characterized by being the values according to atomic % basis;- the amount of component, a between 10 and 65,- the amount of component, b between 2 and 40,- the amount of component, c between 5 and 40,- the amount of component, d between 12.1 and 35,- the amount of component, e between 0 and 40,- the amount of component, f between 0 and 15,- the amount of component, g between 0 and 20,- the amount of component, h between 0 and 20.

7. The alloy of Claim 1 , characterized by having a composite structure with heat treatment.

8. The alloy of Claim 1 , characterized by gaining a composite structure with high hardness and wear resistance at a section thickness above the critical casting thickness.

9. The alloy of Claim 1 , characterized by being a coating with a composite structure having high hardness and wear resistance at a section thickness above the critical casting thickness.

10. The component amounts of Claim 6, characterized by being,- the total of a+b+e+f component amount according to atomic % basis between 20 and 75,- the total of c+g component amount according to atomic % basis between 5 and 40,- the total of d+h component amount according to atomic % basis between 12.1 and 35.

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