Chrome-carbon-iron hard alloy

Abstract

The invention relates to an iron-based chromium-carbon iron hard alloy, wherein a chromium content of 1% - 10%, a carbon content of 0.10% - 0.5%, and additionally a vanadium component of 0.5% - 5%, a tungsten component of 0.5% - 1.5%, a molybdenum component of 0.5% - 1.5% and a niobium component of 0.5% - 1.5% is provided to create an improved alloy, in particular, but not exclusively, for use on glass forming tools.

Description

[0001] The invention relates to a novel iron-based chromium-carbon-iron hard alloy. Chromium-carbon-iron hard alloys are generally known, for example from DE 39 30 340 A1. In this weldable and wear-resistant chromium-carbon-iron hard alloy with 3%–20% chromium, 3%–20% manganese, 2%–30% vanadium and / or niobium, the remainder being carbon and iron, the carbon content of which corresponds at least to the carbide-bound carbon and the matrix of which contains 5%–15% chromium and / or manganese as well as carbon, if present, in solution, the high resistance—even at higher temperatures—under dynamic or high static loads is based on the precipitation of quasi-spherulitic carbides of vanadium and / or niobium in an austenitic to ferritic matrix.

[0002] DE 197 33 306 C1 proposes an additive material for the thermal coating of tribologically stressed components as well as thermally and chemically stressed components in mechanical engineering, apparatus engineering and plant construction. This additive material is a mixture, a gas-atomized alloy, an agglomerated metal powder, a filler wire or strip, a sintered strip or a cast, coated rod electrode, composed of a variety of different components, with a total iron content of at most 12% and the remainder being iron.

[0003] DE 10 2010 004 722 B4 proposes a wear-resistant, heat-resistant material characterized by a hard-phase-rich iron-based cast alloy with a specific chemical composition and a residual iron.

[0004] DE 689 26 758 T2 from EP 0 339 436 B1 relates to an abrasion-resistant sintered iron alloy consisting of a dispersion of hard alloy particles and a method for its production.

[0005] The further DE 690 11 347 T2 from EP 0 377 452 B1 comprises a thermal spraying process for producing glass mold cores, while the further DE 692 27 480 T2 from EP 0 512 805 B1 describes a hardfacing alloy with precipitated metal carbides.

[0006] DE 199 01 170 B4 concerns the use of an iron-based hard alloy in the form of a metal powder atomized after the hard alloy has been melted for the internal armoring of metal cylinders by centrifugal casting or hot isostatic pressing.

[0007] DE 32 07 161 C2, DE 32 38 555 C2 and DE 36 13 389 A1 comprise (sintered) hard alloys or a process for producing a hardfacing welding alloy composition, while DE 26 21 472 C2 describes the use of a hard alloy for cutting, shearing or forming tools, DE OS 26 45 574 a process for producing hard alloys with carbon alloys, and DE 2 005 707 a hard material powder for producing metal-bonded hard material alloys.

[0008] In contrast, DE 398 22 885 U1 comprises a guide ring for a mouth-forming tool for machine-made hollow glass production. Austrian patent AT 140839 describes a steel alloy of iron, carbon, manganese, silicon, and chromium or its substitute metals, while German patent DE 621 740 describes the use of an iron-chromium-nickel-silicon-carbon alloy for highly fire-resistant objects.

[0009] German Patent Application DE 103 393, filed with the Patent Office of the German Democratic Republic, concerns an inner lining of ball mills with grinding plates made of an iron-chromium-carbon alloy, while German Patent Application DE OS 28 37 122 deals with an alloy based on nickel, chromium, carbon, and optionally iron, and its use. European Patent Application EP 0 059 864 A1 relates to a process for the production of amorphous metal alloys based on iron, phosphorus, carbon, and chromium, and the resulting alloy.

[0010] According to the German translation in DE 601 09 528 T2, the further European patent EP 1 172 452 B1 describes a wear-resistant iron alloy, while DE 22 14 146 C3 describes the use of an iron-chromium-carbon alloy for the inner lining of ball mills with grinding plates.

[0011] German patent DE OS 2114 361 deals with a method for manufacturing molded parts from a chromium-carbon-iron alloy, Austrian patent AT 402 942 B with a method and material for producing a metal-containing and thermally sprayed layer, and Swiss patent CH 652 147 with a powdered material for thermal spraying. German patent DE 34 90 081 C2 also deals with a powdered material for thermal spraying, while German patent DE 35 90 031 T1 covers a material for flame spraying and its manufacturing process.

[0012] The object of the present invention is to create an improved alloy, in particular, but not exclusively, for use on glass-forming tools.

[0013] For this purpose, the alloy shown in claim 1 is proposed. The inherent carbides, for example of the form MC, M 7 C 3, etc., are precipitated primarily, eutectically, or secondarily during the solidification of the melt. This makes the alloy particularly wear-resistant.

[0014] Martensitic structural components may also be present; however, these are not crucial for the properties of this hard alloy.

[0015] Advantageously, a tough matrix consisting of an Fe-Cr solid solution and embedded inherent hard materials, mainly carbides, is provided.

[0016] According to one embodiment, an iron-based chromium-carbon-iron hard alloy has a chromium content of 1% - 10%, a carbon content of 0.10% - 0.5%, and additionally a vanadium content of 0.5% - 5%, a tungsten content of 0.5% - 1.5%, a moblybdenum content of 0.5% - 1.5%, and a niobium content of 0.5% - 1.5%.

[0017] Hard alloys are multiphase metallic materials produced by melt metallurgy and further processed using various methods. Their microstructure consists of a relatively tough matrix of the metals iron, cobalt, or nickel, in which hard phases, such as carbides, borides, and, in a few cases, silicides, are embedded [The97, Ber97]. Three groups of hard alloys are distinguished according to the matrix metals (Table 1). In addition to the base metals mentioned above, alloys of other metals are also possible. However, Fe, Ni, and Co are characterized by sufficient solubility for hard-phase-forming elements in the melt and low solubility in the solid state. This leads to precipitation of the hard phases upon cooling of the melt. The base metals also have high melting points.This results in the high hot strength of hard alloys, so that cobalt-based alloys in particular allow maximum application temperatures above 700 °C. Groups of hard alloys Base metal (Ts) Other matrix elements hard phase formers Metalloid Fe(1536°C) Mn Ni Cr, W, Mo, V C,(Si, B) Co(1495°C) |Ni Cu Cr W, Mo C,(Si, B) _Ni(1455°C) Cu Fe, (Co) Cr, Ni B, (Si, C)_

[0018] By combining a metallic matrix with embedded hard phases, materials with a combination of high wear resistance and sufficient fracture toughness can be achieved. The proportion of hard phases is typically between 15 and 45 vol.%. Materials with more than 50 vol.% are produced using powder metallurgy (hard composites).

[0019] The matrix itself, through its volume fraction and composition, is decisive for the mechanical and chemical resistance. The precipitated hard phases largely determine the wear behavior. Furthermore, the bond between the hard phases and the matrix has a significant influence on the mechanical and chemical properties.

[0020] During the solidification of a hard alloy, primary (directly from the melt) and / or eutectic hard phases precipitate. In the highly simplified binary system, consisting of one of the 0g matrix metals and a metalloid (B, C, Si), the formation of a primary metal matrix begins upon solidification of a hypoeutectic melt. This matrix grows into the melt in the form of dendrites. Upon further cooling, the resulting metal cells are surrounded by a eutectic consisting of the metal matrix and eutectic hard phases. In the case of hypereutectic alloys, coarser primary hard phases precipitate first. Further cooling below the eutectic temperature then leads to the formation of the eutectic. Figure 1 schematically illustrates the formation of the microstructure of hard alloys with a eutectic.Besides precipitation from the melt, hard phases can form from the solidified solid solution through further cooling or heat treatment processes; these are referred to as secondary hard phases. Due to their size, however, they are usually attributed to the matrix [The04]. They are significantly smaller than the primary hard phases and have no major influence on wear resistance, for example in grooving wear, but they do improve the supporting effect of the matrix.

[0021] Figure 1Figure 1 shows a schematic representation of the microstructure formation of hard alloys upon solidification with a eutectic according to [Ber97]. S: melt, MM: metal matrix, HP: hard phase, PMM: primary precipitated metal matrix, PHP: primary precipitated hard phase, E: eutectic, M: metal content, T: temperature. The resulting microstructure depends not only on the alloy composition and the temperature range of its formation. The cooling gradient has a significant influence on the microstructure. An increase in the cooling rate results in a finer-grained microstructure than with comparatively slow cooling, as the distance between the dendrites decreases. This also means that the microstructure is strongly dependent on the processing of the hard alloys. The mean network diameter, i.e., the mean diameter of the metal cells, can increase to approximately 100 µm when cooling a hypoeutectic melt if the alloy is processed by sand casting.If we weld the same alloy overlay, mesh diameters can be achieved that are an order of magnitude smaller than in castings [Ber97].

[0022] Metal carbides and borides are particularly suitable as hard phases because their high solubility in the melt contrasts with their low solubility in the solid state. The solidification process therefore leads to the precipitation of primary and / or eutectic hard phases. Of technical importance for hard alloys are the carbides and borides of the elements titanium, niobium, vanadium, chromium, iron, and tungsten.

[0023] The hard phases contained in hard alloys are metal-metalloid compounds in which the atoms of the hard phases are bonded not only covalently via the electron gas but also metallically. This results in coherent or partially coherent interfaces between the matrix and the hard phase, and thus good bonding between the hard phases and the metallic matrix. In covalently bonded hard phases, for example, a sharp boundary arises due to the different bond types between the matrix and the hard phase, resulting in poorer bonding to the matrix material. The hardness of metallic hard phases lies between that of metallic matrices and covalently bonded hard phases, such as boron nitride, which has a hardness in the range of approximately 5000 HV 0.05. Literature reports values ​​for metallic hard phases ranging from approximately 800 HV 0.05 for Ni3B to approximately 4000 HV 0.05 for TiB2 [Ber97].In general notation, hard phases are designated according to their composition as M m X n . X represents the metalloid, M the metal involved in the hard phase (unalloyed hard phase), or several metals (e.g. (Fe, Cr) 3 C, a mixed carbide).

[0024] The hard phases primarily determine the resistance to wear, while the metal matrix has a supporting effect. Wear resistance is mainly determined by the volume ratio of the hard materials in the microstructure, their type, shape, grain size distribution, and insertion direction in relation to the direction of wear. For example, in the case of grooving wear, the hard phase should exhibit higher hardness and fracture toughness than the abrasive [The97]. To prevent the hard phases from being lifted out by the chip, they should also be larger than the groove width. However, coarse hard phases lead to lower fracture toughness in hard alloys.

[0025] The microstructure can be influenced by processing methods. The state of the grain boundaries between the hard phase and the matrix is ​​a parameter of the system and its wear resistance. Hard alloys are primarily cast materials. They are used directly as castings, as cast welding filler material, as mechanically ground or atomized alloy powder, or after the fusing of various components during deposition. In addition to components made of solid material, hard alloys are also suitable for the production of layered composites, especially when the mechanical properties of hard metals preclude their use as structural materials, for example, in large-volume components. The use of hard alloys as layered materials offers cost advantages, as inexpensive materials, such as low-alloy steels, can be used as structural materials.Furthermore, the substrate materials iA exhibit better toughness, thus improving the fracture resistance of the components produced in this way.

[0026] For the production of such composites, both cladding welding processes and thermal spraying processes are particularly suitable. The layer thicknesses produced with these processes range from a few hundred micrometers to several millimeters. The welding or spraying filler materials are typically in powder form. The use of filler wires, i.e., wires in which powder is contained within a sheath of a ductile alloy, enables processing with wire-based processes. In the field of thermal spraying, these include, for example, wire flame spraying or arc spraying processes. The processing of powdered filler materials is carried out using powder flame spraying, high-speed flame spraying, or plasma spraying processes [Lug02].

[0027] Subsequent remelting of the coatings improves their properties, as the pores unavoidable in thermal spray coatings disappear. This results in a reduction of the coating thickness, which must be considered when designing the spraying process. Nickel- and cobalt-based alloys with boron are suitable for subsequent remelting because the eutectics of such alloys have lower melting points compared to steel or cast iron. NiCrBSi alloys and Stellite have gained particular technical importance in this regard. The corrosion behavior of hard alloys is partly determined by the composition of the metallic matrix and the hard phases. The base metal therefore has a significant influence on corrosion resistance. Generally, a higher chemical bond strength leads to improved corrosion resistance.Due to its metallic bonding, the metallic matrix represents the least stable component of the microstructure. The hard phases, with their proportions of metallic and covalent bonding, are significantly more stable and are generally hardly affected by corrosion. The weak point of the microstructure is the interface between the hard phases and the matrix. This interface is a disturbed crystal region that can also be superimposed with tensile residual stresses. Therefore, this is where corrosion begins in wet corrosion conditions. The proportions, size, and distribution of interfaces correspond to those of the hard phases. Thus, the hard phases largely influence the course of corrosion, even though they themselves are generally resistant [Ber97].

[0028] The essential and important elements of the alloy, besides iron, are primarily chromium, vanadium, and carbon. It is temperature-resistant up to 900°C. No phase transformations and associated volume changes occur up to this temperature range.

[0029] The alloy is also corrosion-resistant against both aqueous and temperature-induced corrosion attacks, as the target chromium content is over 20%. Furthermore, only a small portion of the chromium is bound in the form of carbides.

[0030] The carbon for the formation of the carbides is present in dissolved form in the alloy and also comes from the base material during welding (base materials are usually cast iron with up to 3% carbon).

[0031] For coating applications on glass molds and tools, classic cladding processes (PTA, etc.) or modern cladding processes (laser cladding, etc.) are used. The alloy is supplied in powder form, preferably with particle sizes < 250 µm.

[0032] The coating is applied, for example, to glass molds for the production of glass bottles.

[0033] The invention is explained in more detail below with reference to the table. Alloy composition:

[0034] ∘ Fe base ∘ Cr: 1 - 10 % ∘ V: 0,5 - 5% ∘ C: 0,10 - 0,5 % ∘ W: 0,5 - 1,5 % ∘ Mon: 0,5 - 1,5 % ∘ Note: 0,5 - 1,5 %

[0035] The alloy is composed of two components: 1. tough matrix consisting of an FeCr solid solution 2. embedded "native" hard materials, mainly carbides.

[0036] These inherent carbides (of the form MC, MC7, C3) are precipitated during the solidification of the melt (primarily, eutectically, or secondarily). This makes the alloy wear-resistant.

[0037] Martensitic structural components may also be present, but these are not crucial for the properties of this hard alloy.

[0038] The essential and important elements of the alloy, besides Fe, are Cr, V and C.

[0039] This alloy is temperature resistant up to 900°C.

[0040] There are no phase transitions and associated volume changes up to this temperature range. However, when used as a glass forming tool, the continuous operating temperature of 300°C is not exceeded.

[0041] As an example, the welding of such an alloy on a guide ring for glass molds used in the container glass industry is shown here.

[0042] These guide rings are extruded in GG25. This alloy was selected for coating such rings:

[0043] Fe Cr Si C bal 0,75 0,7 0,15

[0044] This alloy is produced as a powder through an inert gas atomization process. The subsequently sieved powder fraction measures -180 to +50 µm and is applied to the ring using powder deposition welding (PTA process). Precise temperature control before and after welding is crucial to prevent cracking.

[0045] Figure 2 shows a cross-section through the armored layer FeCrSiC on GG25 base material.

[0046] Three areas can be identified: a. the unchanged base material GG25, b. a transition zone and c. the outer layer.

[0047] For use as a wear-resistant layer on the guide ring, a hardness of > 400 HV in the applied layer is necessary. The hardness profile, as shown in Table 1, illustrates the hardness in the welded layer and in the transition zone along the indicated line. Fig. 1 .

[0048] Figure 3 shows a hardness profile in the welded layer, transition area and base material.

[0049] A layer hardness of approximately 500 HV is optimal for use as a guide ring in the container glass industry. This is achieved through "guided" martensite formation during welding. The carbon content of the base material GG25 is > 3%. During welding, carbon diffuses into and mixes with the layer, thus enabling the desired martensite hardening. Here, the carbon content of the initial layer is only 0.15%, precisely matched to the expected carbon enrichment during welding. This is how the "guided" martensite formation occurs. The additions of Cr and Si further enhance this effect.

[0050] The aim here is to achieve partial martensite formation in the layer through "this metallurgical guidance" in order to maintain sufficient toughness in the microstructure.

[0051] Cracking can then also be avoided; for this, both the preheating conditions (max. 350°C) and the cooling conditions (slow cooling to room temperature) are important.

[0052] Guide rings treated in this way for the container glass industry show optimal performance with a significant extension of service life.

Claims

1. Iron-based chromium-carbon-iron hard alloy, characterized by that a chromium content of 1% - 10%, a carbon content of 0.10% - 0.5%, and additionally a vanadium component of 0.5% - 5%, a tungsten component of 0.5% - 1.5%, a molybdenum component of 0.5% - 1.5% and a niobium component of 0.5% - 1.5% is provided.

2. Alloy according to claim 1, characterized by that a tough matrix consisting of an Fe-Cr solid solution and embedded inherent hard materials, mainly carbides, is provided.

3. Use of an alloy according to claim 1 or 2 for coating glass molds for glass bottle production.

4. Glass mold for making the mouths of glass bottles, characterized by that which is coated with an alloy according to claim 1 or 2.

5. Powder for coating muzzle shapes, consisting of an alloy according to claim 1 or 2.

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