Hard metal
A WC-based hard metal with an austenitic Fe-Cu-Mn/Ni binder system avoids detrimental phase formation, maintaining mechanical properties comparable to WC-Co hard metals, addressing the challenge of replacing cobalt in hard metal production.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-15
AI Technical Summary
Existing hard metal technologies struggle to achieve comparable properties when replacing cobalt as a metallic binder material with alternative metals or metal alloys, leading to impaired mechanical properties.
A hard metal composition comprising predominantly WC with a metal binder that is predominantly austenitic and composed of Fe, Cu, and optionally Mn or Ni, or a combination of Fe, Cu, and Mn, Ni, without forming detrimental phases, is used, allowing for properties comparable to WC-Co hard metals.
The proposed hard metal composition maintains mechanical properties comparable to WC-Co hard metals without using cobalt, ensuring no phase formation that degrades performance, and can be produced using conventional methods.
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Abstract
Description
[0001] hard metal
[0002] The invention relates to the fields of hard metal materials and ceramic and / or powder metallurgical process engineering and concerns hard metals, such as those that can be used, for example, as cutting material for tools like turning tools, drills and milling tools, and as wear-resistant dies, e.g. in forming or stamping tools, as well as a method for their production.
[0003] Cemented metals are metal matrix composites in which hard particles are held together by a metal matrix. As a result, cemented metals are somewhat less hard than pure hard materials, but significantly tougher. On the other hand, they are harder than pure metals, alloys, and hardened steel, but more brittle (Compressive hard materials, ISBN: 9780080965284).
[0004] Hard materials and cemented metals have been known for a long time. According to Kiefer, R. et al.: Hard Materials and Cemented Metals, Vienna, Springer-Verlag, 1953, pp. 196ff., numerous multi-component carbide systems are known, including ternary and complex systems. "The alloying possibilities for hard carbides in three- and multiple-component systems are extraordinarily numerous." "Generally, one can again distinguish two groups of alloys that are of technical interest. One can combine the carbides of the 4th and 5th groups. Since these carbides are all isotypic, complete miscibility can be expected in three- and multiple-component alloys, with the exception of high-ZrC systems." All cemented metals always contain metal-forming carbides as the hard material. The metallic matrix that holds the hard materials together is often also referred to as a binder or metallic binder.
[0005] In particular, tungsten carbide-cobalt hard metals (WC-Co) are known as standard grades that are the most important in terms of quantity.
[0006] However, in addition to and / or with WC, other hard materials such as vanadium carbide (VC), chromium carbide (C^Cs), titanium carbide (TiC), molybdenum carbide (M02C) and tantalum-niobium carbide (Ta,Nb)C can also be used.
[0007] Regarding the microstructure formation in the production of hard metals, for example from WC-Co, conventional production ideally results in a hard metal microstructure consisting of WC grains in a cobalt-rich matrix with dissolved tungsten and carbon.
[0008] The conventional production of hard metal bodies of various compositions and shapes is carried out as green bodies from the hard metal starting powders with organic binders using pressing processes, extrusion, MIM / CIM or 3D printing. The green bodies are then sintered.
[0009] The use of Co and Ni as materials for the metallic binder in hard metal has long been known.
[0010] However, there have also been long-standing efforts to replace cobalt as a metallic binder material in hard metals.
[0011] By L. Prakash, Proceedings of the 13th th The international Plansee Seminar, edited by H. Bildstein and R. Eck, Metallwerk Plansee, Reutte (1993), Vol. 2, contains a review of the properties of WC cemented carbides with alternative binder systems. In summary, it was reported that iron- or nickel-based binder alloys in WC cemented carbides can replace cobalt for many applications where wear and corrosion are critical.
[0012] According to R. de Oro Calderon et al.: Int. J. of Refractory Metals and Hard Material 117 (2023) 106411, (Co.Ni)-free binders for WC cemented carbides were sought, and numerous investigations were carried out on FeMn binders. The results showed that detrimental eta-carbide phases are formed, which negatively affect the mechanical properties of the binder. According to Z. Zhao et al.: J. of Alloys and Compounds 632 (2015) 729-734, the mechanical properties of WC-Fe-Cu cemented carbides with Cu contents between 0 and 2.5 wt.% were investigated under various sintering conditions. It was found that the hardness and transverse strength of the investigated cemented carbides are essentially independent of the Cu content in the binder; however, the relative density increases with increasing Cu content in the binder.
[0013] JP Cardoso et al: Int. J. of Refractory Metals & Hard Materials 84 (2019) 104990 investigated a WC hard metal with a Cu-AISI304 stainless steel as a binder. The stainless steel contained Fe, Cr, Ni and C.
[0014] A disadvantage of the known state of the art is that replacing Co as a metallic binder material in hard metals with other metals and / or metal alloys does not achieve comparably good properties of the hard metals.
[0015] The object of the present invention is to provide co-free hard metals that have comparably good properties to WC-Co hard metals.
[0016] The problem is solved by the invention specified in the patent claims. Advantageous embodiments are the subject of the dependent claims, and the invention also includes combinations of the individual dependent patent claims in the sense of an AND conjunction, as long as they are not mutually exclusive.
[0017] The hard metal according to the invention consists of at least one hard material, which consists predominantly of WC, and a metal binder, which is at least predominantly austenitic and comprises at least Fe and Cu and Mn or Fe and Cu and Ni or Fe and Cu and Mn and Ni, wherein in the metal binder
[0018] 74.0 to 87.5 wt% Fe,
[0019] 0.5 to 6.0 wt.% Cu
[0020] 12.0 to 20.0 wt% Mn or Mn and Ni or
[0021] 16.0 to 20.0 wt% Ni are present.
[0022] Advantageously, the hard material consists of more than 50 wt% WC, and may also contain TiC, TaC, NbC, VC, ZrC, M02C and / or HfC as additional hard materials. Advantageously, 70 to 96 wt%, and preferably 84 to 94 wt%, of hard material is present.
[0023] Furthermore, it is advantageous that 4 to 30 wt.%, or more advantageously 6 to 16 wt.%, metal binders are present.
[0024] It is also advantageous if the metal binder contains 4 to 5 wt% Cu in each composition, and furthermore 14 to 16 wt% Mn or 16 to 18 wt% Ni or 13 to 16 wt% (Mn + Ni) and the remainder Fe.
[0025] It is also advantageous if the metal binder is 80 to 100% austenitic.
[0026] It is further advantageous if a total of 13.0 to 16.0 wt.% Mn and Ni are present, wherein the proportion of nickel in the metal binder is between 15 wt.% and 65 wt.%, advantageously between 20 wt.% and 45 wt.%.
[0027] It is also advantageous if Mo is present as a further component of the binder in a proportion of 0 to 2.0 wt.%.
[0028] It is also advantageous if the metals in the binder have not formed a chemical bond with the hard material.
[0029] The present invention provides co-free hard metals which have comparably good properties to WC-Co hard metals.
[0030] This is achieved through a hard metal made of at least one hard material and a metal binder.
[0031] According to the invention, the hard material present is at least predominantly WC.
[0032] In addition to WC, other hard materials such as TiC, TaC, NbC, VC, ZrC, M02C or HfC may be present.
[0033] It is also advantageous if the hard metal contains 70 to 96 wt.%, and even more advantageously 84 to 94 wt.% of hard material.
[0034] In addition to the at least one hard material, a metal binder is also present in the cemented carbide according to the invention. Advantageously, 4 to 30 wt.%, and even more advantageously 6 to 16 wt.% of metal binder are present in the cemented carbide.
[0035] The metal binder according to the invention is at least predominantly austenitic and contains Fe and Cu and Mn or Fe and Cu and Ni or Fe and Cu and Mn and Ni.
[0036] According to the invention, each composition contains 4 to 5 wt% Cu and further 14 to 16 wt% Mn or 16 to 18 wt% Ni or 13 to 16 wt% (Mn + Ni) and the remainder Fe.
[0037] Furthermore, it is advantageous if 13 to 16.0 wt% Mn and Ni are present, whereby the proportion of Ni in the metal binder is then advantageously 15 to 65 wt%, preferably between 20 wt% and 45 wt%.
[0038] Advantageously, the metal binder contains 79-82 wt% Fe and 4-5 wt% Cu and 14-16 wt% Mn or Mn and Ni.
[0039] It is advantageous if the austenitic content of the metal binder is 80 to 100%.
[0040] According to the invention, it is important that the metal binder according to the invention predominantly and advantageously as completely as possible has an austenitic crystal structure.
[0041] It is known from the prior art that Fe-based binders in cemented carbides form undesirable phases with the hard material, which impair the properties of the cemented carbides.
[0042] Therefore, it is important according to the invention that the cemented carbide according to the invention contains a metal binder that has not formed a chemical bond with the hard material and has not formed undesirable phases that impair the properties of the cemented carbide.
[0043] Due to the selection of a predominantly, ideally entirely austenitic, iron-based alloy as the metal binder according to the invention, with the proportion of Cu and Mn or Cu and Ni or Cu and Mn and Ni, surprisingly, no phase formation occurs between the hard material and the metal binder, and the properties of the cemented carbide are not impaired and essentially correspond to the properties of cemented carbides with cobalt binders. Accordingly, the cemented carbide according to the invention can be made without the use of cobalt as a component of the binder, without significantly impairing the properties of the cemented carbide.
[0044] The use of Mn or Ni or Mn and Ni, each alongside Cu and Fe, as components of the metal binder in the hard metal according to the invention supports the austenite formation of the metal binder, provided that a completely austenitic metal binder is not already present.
[0045] Furthermore, the use of Mo can advantageously improve the bonding of the metal binder to the hard material in the cemented carbide according to the invention.
[0046] The cemented carbide according to the invention is produced using known methods. The cemented carbide starting powders are mixed with organic binders and processed into a shaped body using pressing, extrusion, MIM / CIM or additive manufacturing processes, and then sintered.
[0047] The invention will now be explained in more detail using an exemplary embodiment.
[0048] Example 1
[0049] The toilet bowl powder, with an average initial particle size of approximately 3 pm, was milled with iron, manganese, and copper powder in a ball mill using a solvent (heptane) at a powder-to-grinding-ball ratio of 1:5 for 24 h. The chemical composition is given in Table 1.
[0050] The powder mixtures were each sintered at 1350 °C for 45 min in a SinterH IP furnace with an Argon (Ar) HIP pressure of 10 MPa.
[0051] After drying, the powders were used to produce flexural fracture bars with a geometry of 45 x 5 x 6 mm. 3 manufactured by means of uniaxial pressing at 200 MPa.
[0052] The flexural fracture bars of all compositions proved to be completely dense under a light microscope. The Vickers hardness was determined according to ISO 3738, and the fracture toughness (Kic) was calculated by measuring the crack lengths according to ISO 28079.
[0053] The results of these investigations into hardness and fracture toughness are given for all examples in Table 2. After sintering, the microstructure of all flexural fracture bars of the compositions according to the invention consisted of the WC hard phase and the metallic binder alloy. According to qualitative X-ray diffractometry, in addition to the hexagonal WC phase, the iron-based metal alloy is predominantly present in the face-centered cubic and thus austenitic crystal structure.
[0054] Example 2
[0055] The production of the flexural fracture bars was carried out according to Example 1 with the different chemical composition for Example 2 from Table 1 and led to the results for hardness and fracture toughness for Example 2 according to Table 2 in the investigations according to Example 1.
[0056] Example 3
[0057] The flexural fracture bars were produced according to Example 1. A different WC powder with an average initial particle size of approximately 1 pm was used. The differing chemical composition for Example 3 is given in Table 1 and, in the tests according to Example 1, led to the results for hardness and fracture toughness for Example 3 shown in Table 2.
[0058] Example 4
[0059] The production of the flexural fracture bars was carried out according to Example 1 with the different chemical composition for Example 4 from Table 1 and led to the results for hardness and fracture toughness for Example 4 according to Table 2 in the investigations according to Example 1.
[0060] Example 5
[0061] The production of the flexural fracture bars was carried out according to Example 1 with the different chemical composition for Example 5 from Table 1 and led to the results for hardness and fracture toughness for Example 5 according to Table 2 in the investigations according to Example 1.
[0062] Comparative example 6
[0063] The production of the flexural fracture bars was carried out according to Example 1 with the differing chemical composition for Comparative Example 6 from Table 1 and, in the tests according to Example 1, led to the results for hardness and fracture toughness for Comparative Example 6 according to Table 2. Comparative Example 7
[0064] The flexural fracture bars were produced according to Example 1. A different WC powder with an average initial particle size of approximately 1 pm was used. The differing chemical composition for Comparative Example 7 is given in Table 1 and, in the tests according to Example 1, led to the results for hardness and fracture toughness for Comparative Example 7 shown in Table 2.
[0065] Table 1. Chemical compositions
[0066] Table 2 Properties
Claims
Patent claims 1. Hard metal comprising at least one hard material consisting predominantly of WC, and a metal binder which is at least predominantly austenitic and comprises at least Fe and Cu and Mn or Fe and Cu and Ni or Fe and Cu and Mn and Ni, wherein in Metal binder 74.0 to 87.5 wt% Fe, 0.5 to 6.0 wt% Cu, 12.0 to 20.0 wt% Mn or Mn and Ni or 16.0 to 20.0 wt% Ni are present.
2. Hard metal according to claim 1, wherein the hard material consists of more than 50 wt.% WC and may contain further hard materials TiC, TaC, NbC, VC, ZrC, M02C and / or HfC.
3. Hard metal according to claim 1, wherein 70 to 96 wt%, advantageously 84 to 94 wt%, hard material is present.
4. Hard metal according to claim 1, wherein 4 to 30 wt.%, advantageously 6 to 16 wt.%, metal binder is present.
5. Hard metal according to claim 1, wherein the metal binder in each composition contains 4 to 5 wt.% Cu and further contains 14 to 16 wt.% Mn or 16 to 18 wt.% Ni or 13 to 16 wt.% (Mn + Ni) and the remainder Fe.
6. Hard metal according to claim 1, wherein the metal binder is 80 to 100% austenitic.
7. Hard metal according to claim 1, in which a total of 13.0 to 16.0 wt.% Mn and Ni are present, wherein the proportion of nickel in the metal binder is between 15 wt.% and 65 wt.%, advantageously between 20 wt.% and 45 wt.%.
8. Hard metal according to claim 1, wherein Mo is present as a further component of the binder in a proportion of 0 to 2.0 wt.%.
9. Hard metal according to claim 1, wherein the metals of the binder have not formed a chemical compound with the hard material.