EP2374560A1 - Wear-resistant material - Google Patents

Abstract

A wear-resistant material comprises (in weight%) carbon (0.3-3.5), nitrogen (0.05-4), oxygen (0.002-0.25), niobium/tantalum (3-18), and remainder of metallic elements and impurities. A microstructure of the material comprises a metal matrix and hard phases embedded in the matrix. The hard phases comprise carbide, nitride, carbonitride and/or oxide carbonitride, where hard phases have diameter of 0.2-50 mu m. An independent claim is also included for a method for producing a wear-resistant material.

Description

The invention relates to a wear-resistant material containing carbon (C), nitrogen (N), oxygen (O), niobium and / or tantalum (Nb / Ta) as well as metallic elements and impurities remainder with a structure consisting of a metal matrix and in these Hartphasen stored.

According to the technical approach wear-resistant, metallic materials consist of a tough or tough matrix and distributed in this hard phases, which are usually formed as interstitial compounds.

A wear-reducing effect of hard phase deposits is well known, with a higher hard phase content in the matrix as much as possible reducing abrasive removal from the workpiece surface when the support force for the hard particles and the matrix hardness are high.

According to the prior art are wear-resistant iron-based materials, eg. Cold work steels, from a hard, preferably thermally tempered metal matrix with distributed in this, precipitated from the residual melt of the alloy during solidification, carbides.

Carbide formation in a ledeburitic solidification of an alloyed melt in a cast billet may also result in coarse hard phases with inhomogeneous distribution in the material due to a low solidification rate in the center thereof and segregation.

In order to achieve a higher concentration of hard phases in the material, in particular with a uniform distribution in this, it is known to apply powder metallurgical production methods. Essentially, in these PM processes, an alloyed liquid melt after flowing out of a nozzle is separated by high-pressure gas jets into small droplets which naturally cool at high speed and thereby precipitate fine hard phase particles upon solidification. By a hot isostatic Pressing (HIP) or by deformation of the powder in a container, a production of a largely dense material with a high proportion of uniformly distributed hard phases with a small grain size takes place.

An increase in the wear resistance by increasing the volume fraction of hard phases in the matrix of a material and in consequence of an increase in the concentration of the hard phase-forming elements, however, has procedural and reaction kinetic limits. Primary precipitations in the liquid metal can lead to a reduction in the outflow of the same from the nozzle or to a total growth of the passage opening during the atomization process and thus adversely affect the manufacturability. Larger alloy overheating in the storage vessel of a plant for the production of metal powder may also have metallurgical and / or reaction kinetic disadvantages.

Due to the demand for highly wear-resistant materials, which should possibly have a superior corrosion resistance, alloys have been proposed which have a high content of carbide formers, in particular monocarbide formers, with a corresponding carbon content and a chromium concentration in the matrix of more than 12.0 wt .-%.

In the DE 42 02 339 B4 For example, a corrosion-resistant, highly wear-resistant, hardenable steel with niobium contents of 5.0 to 8.0% Nb is proposed, which can be produced without the use of a powder metallurgical process.

In order to achieve a wear-resistant matrix with a hard, martensitic structure and a high carbide content, even with slow cooling of a component, is according to DE 10 2005 020 081 A1 a high content of the elements chromium, molybdenum, vanadium, and especially nickel provided because these elements in the ZTU graph move the perlite nose to the right.

Alloys in which no expensive chromium is to be lost by carbide formation discloses the DE 42 31 695 A1 and suggests using a PM tool steel with 1 to alloy up to 3.5 wt .-% nitrogen.

Nitrogen for hard phase formation is considered an advantageous measure for the production of wear-resistant materials in the WO 2007/024 192 A1 proposed.

Based on the technical requirements and the technological state of the art, the invention sets itself the goal of specifying a material which has a high resistance to abrasion under abrasion stress. Advantageously, this material in an alloy variant should also be resistant to chemical corrosion.

Another object of the invention is to provide a method for producing a material with greatly reduced wear and optionally desired corrosion properties or high corrosion resistance.

The object of the invention mentioned at the outset is essentially achieved by a material containing in% by weight: Carbon (C) more than 0.3 to 3.5 Nitrogen (N) 12:05 to 4.0 Oxygen (O) more than 0002 to 12:25 Niobium / tantalum (Nb / Ta) 3.0 to 18.0

as well as metallic elements and impurities as the remainder
with a structure consisting of a metal matrix and embedded in these hard phases, with the proviso that the hard phases are formed as carbides and / or nitrides and / or carbonitrides and / or Kohlenstoffkarbonitride and have a diameter of at most 50 microns and at least 0.2 microns ,

The advantages of the wear-resistant material of the invention consist essentially in the fact that due to the niobium / tantalum concentration of 3.0 to 18.0 wt .-% and the carbon content of 0.3 to 3.0 wt .-% and the nitrogen content of 0.05 to 4.0 wt .-% high-hardness niobium and / or tantalum monocarbides, mononitrides or monocarbonitrides are present in a homogeneous distribution with a small diameter and thus a high abrasion resistance is achieved.

With lower contents of carbon than 0.3% by weight and nitrogen than 0.05% by weight, the formation potential of compounds with contents of 3.0 to 18.0% by weight Nb / Ta can not be sufficiently exploited, on the other hand higher contents than 3.0 to 4.0%. % of carbon and nitrogen compounds degrading.

The oxygen content of 0.0020 to 0.25 in the material acts on the one hand as a formation nucleus for the hard phase with respect to hard particles with specific, small size in a homogeneous distribution in the matrix and on the other hand as a separate hard material former.

Higher oxygen contents than 0.25 wt .-% embrittle the hard phases, whereas lower contents than 0.0020 wt .-% have no pronounced germination.

It is important according to the invention that the hard material particles have a diameter of at most 50 μm, because with larger phases the danger of breaking them out of the matrix is suddenly increased. Smaller diameters than 0.2 μm of the hard phases provide only a slight, abrasion-reducing effect.

If, as in the invention, the matrix of the wear-resistant alloy has a martensitic microstructure, then the material itself has an increased abrasion-reducing hardness, minimizing as far as possible the risk of breaking hard phases out of the structure during wear.

erfüllt, und die Zahl U größer als 6, jedoch kleiner als 10 ist, als besonders vorteilhaft herausgestellt.In a development of the invention, for a material with high resistance to abrasion under abrasion stress and with high corrosion resistance, a composition of in% by weight has Carbon (C) 0.5 to 2.5 Nitrogen (N) 12:15 to 0.6 Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 2.0 Chrome (Cr) 10.0 to 20.0 Niobium / tantalum (Nb / Ta) 3.0 to 15.0 Molybdenum (Mo) 0.5 to 3.0 Vanadium (V) 0.1 to 1.0 Titanium (Ti) 0001 to 1.0 Iron (Fe) rest and production-related impurities, with the proviso that the relationship between carbon content and the respective concentration of niobium / tantalum and vanadium and titanium has a value formed from $$\mathrm{\%}\mathrm{C}\mathrm{=}\mathrm{0.3}\mathrm{+}\frac{\mathrm{\%}\mathrm{Nb}\mathrm{+}\mathrm{2}\mathrm{x}\left(\mathrm{\%}\mathrm{V}\mathrm{+}\mathrm{\%}\mathrm{Ti}\right)}{\mathrm{U}}$$

fulfilled, and the number U is greater than 6, but less than 10, as particularly advantageous.

The concentrations of the alloying metals are coordinated in this material with respect to the carbon activity and the carbide formation kinetics of the respective elements, the contents of the monocarbide formers being decisive for the intended carbon concentration. Nitrogen is limited with a content of 0.6 wt .-% to the top, because in the given case, the hard phases should be designed mainly as carbides. Below 0.15 wt.% Nitrogen, the solidification effect of the matrix is too low, so that the content limits in wt.% Are 0.15 to 0.6 nitrogen.

Silicon acts as a deoxidation metal and influences the microstructural transformation of the alloy during the heat treatment. A minimum content of 0.2% by weight of Si is important in terms of effective oxide formation, whereas higher contents than 1.5% by weight adversely affect toughness.

A manganese content of 0.3% by weight or more is intended for setting sulfur in the metal, with more than 2.0% by weight of Mn promoting disadvantageous austenite stability.

Chromium and molybdenum provide corrosion resistance of the alloy at minimum concentrations of 10.0 and 0.5 wt%, but may also be effective as carbide formers. Higher contents than 20% by weight Cr and 3.0% by weight Mo disadvantageously lead to a stabilization of ferrite in a heat treatment.

Vanadium and titanium should not exceed contents of 1.0 wt .-%, because carbides of these elements to a large extent dissolve Cr or incorporate into the crystal lattice, which can cause depletion of Cr in the edge region of the matrix.

This local chromium depletion interferes with the formation of a stable passive layer on the surface, thereby deteriorating the corrosion resistance of the alloy. In% by weight 0.1 vanadium and 0.001 titanium are favorable for the formation of monocarbide nuclei.

The elements niobium and tantalum are elements that form in the alloy from a content of 3.0 wt .-% hard, the wear resistance of the material promoting monocarbides. It is important that these elements Nb / Ta show only a slight tendency to incorporate further elements, in particular chromium, in the carbide or carbonitride formation in the crystal lattice, so that in the vicinity of these hard phases no depletion of the matrix of alloy components, especially of chromium and Molybdenum, arises and thus no adverse effect on the corrosion resistance of the material is formed.

erfüllt ist, und die Zahl U1 größer als 4 und kleiner als 8 ist.According to a further embodiment of the invention, a low wear and high corrosion resistance of the material is achieved, if this Carbon (C) more than 0.3 to 1.0 Nitrogen (N) 1.0 to 4.0 Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 1.5 Chrome (Cr) 10.0 to 20.0 Niobium / tantalum (Nb / Ta) 3.0 to 15.0 Molybdenum (Mo) 0.5 to 3.0 Vanadin (V) 0.1 to 1.0 Titanium (Ti) 0001 to 1.0 Iron (Fe) rest and production-related impurities,
with the proviso that the relationship between nitrogen content and the respective concentration of niobium and vanadium has a value formed from $$\mathrm{\%}\mathrm{N}\mathrm{=}\mathrm{0.3}\mathrm{+}\frac{\mathrm{\%}\mathrm{Nb}\mathrm{+}\mathrm{2}\mathrm{x}\left(\mathrm{\%}\mathrm{V}\mathrm{+}\mathrm{\%}\mathrm{Ti}\right)}{\mathrm{U}1}$$

is satisfied, and the number U1 is greater than 4 and less than 8.

The high nitrogen content of 1.0 to 4.0 wt .-% at carbon concentrations of 0.3 to 1.0 wt .-% leads to substantially nitrides formed hard phases, whereby the chromium and molybdenum induced passive layer formation and corrosion resistance are promoted.

erfüllt, und die Zahl U2 größer als 6 und kleiner als 10
und die Zahl U3 größer als 9 und kleiner als 17 sind.Taking into account the chromium content in terms of corrosion resistance and in the orientation of the wear resistance to substantially carbides, according to a further embodiment of the invention, a material can be provided cheaply and economically, which in wt .-% Carbon (C) 0.5 to 3.0 Nitrogen (N) 12:15 to 0.6 Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 2.0 Chrome (Cr) 10.0 to 20.0 Niobium / tantalum (Nb / Ta) 3.0 to 15.0 Molybdenum (Mo) 0.5 to 3.0 Vanadin (V) 0.1 to 1.0 Titanium (Ti) 0001 to 1.0 Iron (Fe) rest with production-related impurities
with the proviso implies that the relationship between carbon content and the respective concentration of niobium, vanadium, titanium and chromium has a value formed from $$\mathrm{\%}\mathrm{C}\mathrm{=}\mathrm{0.3}\mathrm{+}\frac{\mathrm{\%}\mathrm{Nb}\mathrm{+}\mathrm{2}\mathrm{x}\left(\mathrm{\%}\mathrm{V}\mathrm{+}\mathrm{\%}\mathrm{Ti}\right)}{\mathrm{U}2}+\frac{\mathrm{Cr}}{\mathrm{U}3}$$

fulfilled, and the number U2 greater than 6 and less than 10
and the number U3 is greater than 9 and less than 17.

erfüllt ist, wobei die Zahlenwerte U4 = 6 bis 10 / U5 = 80 bis 100 sind.Be of a material according to the invention in addition to high wear resistance Also, a high hot hardness and the like. Toughness required, as is of special importance for cutting tools, the alloy may have the following composition and ratios of the elements in wt% with lowered chromium contents Carbon (C) 1.0 to 3.5 Nitrogen (N) 12:05 to 0.4 Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 1.0 Chrome (Cr) 2.5 to 6.0 Niobium / tantalum (Nb / Ta) 3.0 to 18.0 Molybdenum (Mo) 2.0 to 10.0 Tungsten (W) 0.1 to 12.0 Vanadin (V) 0.1 to 3.0 Cobalt (Co) 0.1 to 12.0 Iron (Fe) rest with production-related impurities
with the proviso that the relationship between carbon content and the respective concentration of niobium / tantalum as well as vanadium and titanium has a value formed from $$\mathrm{\%}\mathrm{C}\mathrm{=}0.6\mathrm{+}\frac{\mathrm{\%}\mathrm{Nb}\mathrm{+}\mathrm{2}\mathrm{x}\left(\mathrm{\%}\mathrm{V}\mathrm{+}\mathrm{\%}\mathrm{Ti}\right)}{\mathrm{U}4}+\frac{2x\%\mathrm{Not\; a\; word}+\%\mathrm{W}}{\mathrm{U}5}$$

is satisfied, wherein the numerical values U4 = 6 to 10 / U5 = 80 to 100 are.

The highly wear-resistant tool material, which is based on a type of high-speed steel alloy, can be easily tempered to high hardness values and has outstanding toughness despite its high hardness. Particularly pronounced is the wear resistance of the cutting tools formed from this alloy, which tools thus have a particularly long service life in coarse and interrupted section.

The inventive method of the type mentioned above is determined such that in a first step, a metallic liquid alloy containing niobium / tantalum (Nb / Ta) with a concentration of 3.0 to 18.0 wt .-%, and a content of carbon and / or nitrogen, in which no primary excretions formed on carbides and / or nitrides above the Verdüsungstemperatur or liquidus temperature, is atomized to powder material, after which the powder subjected to a process for increasing the carbon content and / or the nitrogen content and / or the oxygen content and subsequently subjected to a Heißkompaktieren, in particular a hot isostatic pressing Alternatively, the pellet or HIP body is subjected to a hot deformation and / or a heat treatment alternatively.

Because primary carbide and nitride precipitates can be formed at high Nb / Ta contents, it is important in accordance with the present invention to maintain carbon and nitrogen levels below the limit for precipitate formation in an otherwise fully composite liquid master alloy, and this liquid metal, particularly by Nitrogen, to atomize powder material. A solid metal powder obtained in this way is subsequently carburetted in a targeted manner at elevated temperature by suitable means and / or its nitrogen content and / or oxygen content is increased to intended levels. Such a powder adjusted in the composition according to the invention is enclosed in containers according to the prior art, can be compacted by hot isostatic pressing (HIPing) or deformation at high temperature and brought to desired dimensions.

The method according to the invention has the advantage that materials with a high carbide-nitride or carbonitride hard material content can be produced, the hard-material particles having small diameters and homogeneous distribution in the matrix. The matrix elements can by a thermal tempering or by hardening and tempering of the material impart this high strength and prevent stripping or breaking the larger, optimized hard particles as far as possible. As a result, a particularly pronounced wear resistance of the material is achieved.

A carburizing and / or an increase in the nitrogen content when adjusting the oxygen content of the pre-alloyed metal powder according to the invention by admixed, elemental carbon and / or by a carbon and / or nitrogen and / or oxygen-emitting atmosphere, in particular at elevated Temperature before or during a hot compaction.

In one embodiment of the invention, other hard material particles with a size of 2 to 50 microns to an extent of up to 25 vol .-% can be added to the powder material, which are effective in reducing wear for the given material.

By way of examples which represent merely exemplary ways, the properties of the alloy according to the invention are to be described in more detail in comparison with known materials.

Tab. 1 on page 11 shows the composition of two commercially available, wear-resistant alloys with the designations X190 CrVMo 20 4 1, X90 CrVMo 18 1 1, of corrosion-resistant, inventive alloys with the designations A, B, C, and of cutting materials according to the invention with the designations D, E, F.

The commercial alloys were made by the PM method with a HIP block (hot isostatic pressed) of greater than 6 times.

Powders for the samples designated A, B, C were made from alloys having the following main components in wt%: description Si Mn Cr Not a word V W Nb Co Fe A 12:43 12:42 11.92 2.21 12:08 12:07 9:02 12:08 rest B 12:51 12:44 16:41 2.19 12:09 12:07 9:56 12:05 rest C 12:43 12:42 11.92 2.21 12:05 12:06 9:02 12:08 rest produced by atomizing by means of nitrogen gas.

Atomization with nitrogen was further carried out using melts designated D, E, F with the main constituents in% by weight: description Si Mn Cr Not a word V W Nb Co Fe D 12:30 12:40 4.15 2.94 1:52 2.13 3:34 12:12 rest e 12:28 12:35 3.95 2.84 1:47 2.23 3:45 8.21 rest F 00:37 12:33 3:58 4.10 1.84 5:07 10.73 7:07 rest

As carburizing agents were used on a trial basis for the materials with the designations A to C:
CH ₄ + O
Graphite (admixed) and nitrogen + O
CH ₄ + nitrogen + O, wherein the metal powders about 10% NbC was mixed with a particle size of 28 .mu.m.

• CO + CH₄ + O
• CO + N + O
• Graphit + CO + N + O

The metal powders of the further alloys D to F were treated in the experiments with the following carburizing and nitriding agents:

• CO + CH ₄ + O
• CO + N + O
• Graphite + CO + N + O

Alloying of the alloy powders with carbon, nitrogen and oxygen was carried out at elevated temperature.

The alloyed metal powder was then placed under nitrogen atmosphere in steel containers and knock compacted, followed by welding of the containers and hot isostatic pressing at a temperature of 1165 ° C.

After hot deformation of the HIP block, the product was sampled, analyzed (Table 1) and examined, with important results in Fig. 1 to Fig. 3 are reproduced. Tab. 1 description C N Si Mn Cr Not a word V W Nb Co X190 CrVMo 20 41 1.90 12:20 0.70 12:30 8:00 pm 1:00 4:00 0.60 - - X90 CrVMo 18 11 0.90 12:01 12:40 12:40 18:00 1.10 1:00 12:06 - - A 1:45 12:18 12:42 12:41 11.76 2.18 12:08 12:07 8.90 12:08 B 30.2 12:19 12:50 12:43 16.5 2.14 12:09 12:07 9:35 12:05 C 1:45 12:18 12:42 12:41 11.76 2.18 12:05 12:06 8.90 12:08 D 1.30 12:08 12:30 12:40 4.10 2.90 1:50 2.10 3.30 12:12 e 1:40 12:07 12:28 12:35 3.90 2.80 1:45 2.20 3:40 8.10 F 2:45 12:08 12:36 12:32 3:50 4:00 1.80 4.95 10:48 6.90

Tab. 1 shows the chemical composition of known materials (X190 CrVMo 20 4 1 and X90 CrMoV 18 1 1) and those of steel samples according to the invention

• Das Korrosionsverhalten der Legierungen wurde anhand von Stromdichte-PotentialKurven an den Proben nach ASTM G65 in 1 n H₂SO₄, 20°C ermittelt, wobei eine Abschreckung derselben von 1100°C bzw. 1070°C und ein Anlassen bei 200°C erfolgten.

Corrosion behavior:

• The corrosion behavior of the alloys was determined from current density potential curves on the samples according to ASTM G65 in 1N H ₂ SO ₄ , 20 ° C, with a quenching of the same from 1100 ° C and 1070 ° C and a tempering at 200 ° C. ,

How out Fig. 1 shows, in the relevant potential range of about -300mV to + 300mV, the comparative alloy X190 CrVMo 20 4 1 essentially the highest passive current density in comparison with the inventively assembled samples A, B, C, which reveals their improved corrosion behavior.

Fig. 2 shows the hardness of the differently composite alloys after hardening as a function of the tempering temperature after two tempering.

The respective hardening temperature can be taken from the designation field for the alloys.

In comparison with X190 CrVMo 20 4 1, the materials A and C of the alloy according to the invention on a comparatively low tempering hardness, because their respective carbon content of improved corrosion resistance due to (see Fig.1 ) was chosen low.

The material hardness of the alloys D, E and F are significantly higher in the range of tempering temperatures between 500 ° C and 600 ° C, which discloses a clear superiority of the same for use of, for example, cutting and forming elements.

Fig. 3 shows the wear behavior of the samples made from the alloys, determined according to the VDI Progress Reports "Nitrogen-alloyed Tool Steels", Series 5, No. 188 (1990), p. 129 described pin-disk test with Flint 80s

Grain. The hardnesses of the samples are above the respective bars in Fig. 3 specified. Both the corrosion resistant alloy B and the alloys E and F according to the invention show superior resistance to wear, indicating a correspondingly favorable choice of carbon and niobium contents.

Claims (4)

Wear-resistant material with high hot hardness and toughness, in particular for cutting tools, containing in% by weight: Carbon (C) 1.0 to 3.5 Nitrogen (N) 12:05 to 0.4 Oxygen (O) more than 0002 to 12:25 Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 1.0 Chrome (Cr) 2.5 to 6.0 Niobium / tantalum (Nb / Ta) 3.0 to 18.0 Molybdenum (Mo) 2.0 to 10.0 Tungsten (W) 0.1 to 12.0 Vanadin (V) 0.1 to 3.0 Cobalt (Co) 0.1 to 12.0 Iron (Fe) rest with production-related impurities
with the proviso that the relationship between carbon content and the concentration of niobium / tantalum as well as vanadium and titanium has a value formed from $$\mathrm{\%}\mathrm{C}\mathrm{=}0.6\mathrm{+}\frac{\mathrm{\%}\mathrm{Nb}\mathrm{+}\mathrm{2}\mathrm{x}\left(\mathrm{\%}\mathrm{V}\mathrm{+}\mathrm{\%}\mathrm{Ti}\right)}{\mathrm{U}4}+\frac{2x\%\mathrm{Not\; a\; word}+\%\mathrm{W}}{\mathrm{U}5}$$

fulfilled, wherein the numerical values U4 = 6 to 10 and U5 = 80 to 100 and the structure consists of a metal matrix and embedded in these hard phases, the hard phases are formed as carbides and / or nitrides and / or carbonitrides and / or oxide carbonitrides and a Diameter of at most 50μm and at least 0.2μm have. The wear resistant material of claim 1, wherein the matrix has a martensitic structure. A process for producing a wear-resistant material with high hot hardness and toughness, in particular according to claim 1 or 2, wherein in a first Step a metallic liquid alloy containing: Silicon (Si) 0.2 to 1.5 Manganese (Mn) 0.3 to 1.0 Chrome (Cr) 2.5 to 6.0 Niobium / tantalum (Nb / Ta) 3.0 to 18.0 Molybdenum (Mo) 2.0 to 10.0 Tungsten (W) 0.1 to 12.0 Vanadin (V) 0.1 to 3.0 Cobalt (Co) 0.1 to 12.0 Iron (Fe) rest and production-related impurities,
and a content of carbon and / or nitrogen at which no primary precipitations of carbides and / or nitrides are formed above the atomization or liquidus temperature is atomized to powder material, after which the powder is subjected to a process for increasing the carbon content to 1.0 to 3.5 wt. % and / or of the nitrogen content to 0.05 to 0.4 wt .-% and / or the oxygen content to more than 0.002 to 0.25 wt .-% is subjected to and below a hot compacting, esp. A hot isostatic pressing thereof takes place and the compact or HIP Body is subjected alternatively to a hot deformation and / or a heat treatment. A method of making a wear resistant material according to claim 3, wherein the powder is mixed with elemental carbon and / or treated in a carbon and nitrogen releasing atmosphere, especially at elevated temperature, and subsequently compacted.

Images