Powder mixture

Abstract

The invention relates to a powder suitable for producing a wear-resistant and corrosion-resistant layer, comprising: a) a mixture of a first component selected from the group consisting of carbides, carbonitrides, nitrides and mixtures thereof of Ti and a second component selected from the group consisting of carbides, carbonitrides, nitrides and mixtures thereof of Mo, W, V, Nb, or b) a solid solution, or c) a mixture of a) and b) wherein the total amount of a) or b) or c) is at least 60 wt.%, preferably 70 wt.% to 99 wt.%, where in a) the weight ratio of the first component to the second component is 70: 30 to 98: 2, where in b) the weight ratio of Ti to the second metal M is 70: 30 to 98: 2, an organic binder, and c) a mixture of a) and b), preferably 70 wt.% to 99 wt.%, where in a) the weight ratio of the first component to the second component is 70: 30 to 98: 2, and where in b) the weight ratio of Ti to the second metal M is 70: 30 to 98: 2. Wherein the content of the metal binder in the powder is up to 15 wt.%, preferably up to 5 wt.%.

Description

[0001] This invention relates to powder mixtures for producing wear-resistant and corrosion-resistant layers, particularly coatings. Background Technology

[0002] In the tribological system of a brake, the surface of the brake pads comes into contact with the surface of the brake disc under the application of mechanical braking force. The interaction between the frictional materials causes abrasive wear, and under the influence of ambient humidity and / or corrosive media from the surrounding environment, corrosion and erosion of the brake disc surface occur, leading to particulate matter emissions.

[0003] According to the latest Euro 7 standard, the new emission standard rules are expected to bring emission limits for motor vehicles, requiring a significant reduction in particulate matter emissions from July 2025.

[0004] Therefore, wear-resistant friction materials are of particular interest in reducing braking emissions.

[0005] To increase the wear resistance of the brake tribological system, brake discs are mainly composed of gray cast iron, with one or more coatings applied to them. If more than one coating is applied, the top layer is called the "topcoat".

[0006] Conventional coatings may contain Ni from stainless steel components, which can lead to sensitization (Ni allergy) in humans.

[0007] It is known in the art that wear resistance can be improved by adding carbides such as Cr3C2, WC, or TiC as a hard component to the top layer of a coating and embedding it into a stainless steel matrix (FeCr matrix). The widespread use of carbide composites as wear-resistant materials is attributed to their unique combination of desired properties, such as high wear resistance and stiffness, considerable strength, and relatively low production costs.

[0008] For example, WO 2020 / 234146 A1 discloses a friction braking element for a motor vehicle that includes a variety of carbide wear-resistant layers, including chromium carbide, niobium carbide, titanium carbide, tungsten carbide, molybdenum carbide and vanadium carbide.

[0009] Another example is disclosed in US 2013 / 136941 A1, which describes a multifunctional coating for a metal substrate comprising two layers, one of which contains particles distributed within the metal or alloy matrix. Suitable particles may comprise metal carbides, metal nitrides, metal borides, metal silicides, ceramics, cemented carbides, or cast carbides.

[0010] WO 2021 / 224308 A1 describes a vehicle braking component having a metal substrate surface with a coating comprising a hard material, such as tungsten carbide, chromium carbide, titanium carbide, vanadium carbide, or silicon carbide.

[0011] To create a topcoat on a metal substrate, an alloying material containing carbide-forming metals such as Ti, V, and Cr can also be used. This material is melted during the process, and during cooling, the carbide-forming metal, along with added carbon or carbon from the steel alloy, precipitates as finely distributed carbides.

[0012] For example, this coating can be applied via laser cladding. During laser cladding, powdered or filamentous raw materials are coated onto a substrate by melting and solidifying them using a laser. This method is often used to improve the mechanical properties of materials or increase their corrosion resistance.

[0013] EP 4 029 966 A1 discloses a method for producing gray cast iron brake discs, wherein a coating containing carbides is applied to the brake surface by laser cladding.

[0014] DE 10 2020 203 412 A1 describes a method for producing a protective topcoat on a brake disc by laser cladding of NbC or Cr3C2 metal matrix powder.

[0015] In addition, WO 2021 / 007209 A1 discloses an iron-based raw material for various deposition processes (such as ultra-high-speed laser cladding) to form coatings with specific microstructure characteristics and performance properties.

[0016] It was also found that high carbide content can reduce the risk of metal pick-up unit (MPU). MPU is a problematic phenomenon in automotive disc brakes. MPU typically forms metal clumps on the surface of the brake pads. If the brake pads have MPU, they can cause the brake disc rotor to slot during braking, generating braking noise and degrading braking performance. MPU is a phenomenon that depends on many factors (such as climate, general road conditions, etc.), and is therefore difficult to quantify.

[0017] However, it turns out that high carbide content not only improves the wear resistance of the top layer of the brake disc, but is also associated with a variety of problems.

[0018] One problem is that the likelihood of cladding material decreases when more carbides are added, because the material becomes very prone to cracking as the carbide content increases.

[0019] If a crack connects the surface to the substrate, a crack penetrating the coating is fatal to corrosion resistance. Corrosive media can reach the substrate and corrode the bond area, causing the substrate to rust, weakening the bond between the substrate and the coating, and ultimately causing the coating to delaminate from the substrate. This will visually and functionally destroy the coating.

[0020] In the past, efforts have been made to produce wear-resistant and corrosion-resistant topcoats.

[0021] For example, WO 2022 / 223835 A1 discloses a mixture of stainless steel powder with chromium carbide and at least one other carbide with a melting point higher than chromium carbide. The resulting topcoat is described as containing at least 30 vol% of the two dispersed carbides. WO 2022 / 223835 A1 mentions that the resulting topcoat is substantially free of cracks; however, experimental data clearly show the presence of cracks in the coating after laser cladding.

[0022] Furthermore, commercially available carbide-based powders with an FeCr matrix are marketed as environmentally friendly alternatives to nickel- or cobalt-based hard metals used in the production of wear-resistant topcoats. For example, the commercially available powder GTV 81.61.8S (GTV Verschleißschutz GmbH) contains 70 wt.% TiC and 30 wt.% FeCr. Carbide powders such as TiC / FeCr or NbC are typically agglomerated and sintered or crushed and sintered to produce coatings. However, crack-free topcoats made from the aforementioned commercially available powders contain no more than 30 vol.% carbides in a stainless steel matrix.

[0023] To date, the highest carbide content in a laser cladding top coating that can be used on brake discs without any cracks is approximately 30 vol. % (based on total coating volume).

[0024] To avoid cracking, various means and methods have been explored to generate stress-free and crack-free protective coatings. Furthermore, there is a particular need for Ni-free metal alloys with sufficient carbide content to meet future emission standards.

[0025] However, no suitable pre-material has yet been found for producing coatings with a high carbide content of at least 30 vol.% and low crack sensitivity.

[0026] Therefore, it has been found that the above-mentioned problems make it particularly difficult to formulate powders for producing crack-free wear-resistant coatings.

[0027] Cermets (combinations of metals and Ti compounds such as TiC and TiN) are alternative materials that exhibit excellent hardness and wear resistance.

[0028] For example, Qiu et al. described the effect of Mo2C addition on the tribological properties of Ti(C,N)-based cermets. The cermets mentioned in this publication are used as compacts for cutting tools or molds, rather than as coatings. The cermets contain significant amounts of metallic binders. In this study, 6 wt.% Mo2C was shown to increase hardness. Excessive carbides were also reported to decrease toughness and increase the risk of cracking (Qiu et al., 2023, Materials, 16, 5645, doi: 10.3390 / ma16165645).

[0029] It was also reported that the properties and microstructure of cermets depend on the composition of the prematerial in terms of carbon-nitrogen ratio, stoichiometry of the hard phase, and a significant amount of metallic Ni / Co binder (Ettmayer et al., 1995, International Journal of Refractory Metals & Hard Materials, 13, 343-351, doi: 10.1016 / 0263-4368(95)00027-G).

[0030] Lengauer and Scagnetto provide a metallurgical overview of the microstructure formation of Ti(C,N)-based cermets during sintering. Alloys of ferrous metals Fe, Co, and Ni are disclosed as commonly used as metallic binders, as well as multi-component binders such as Co, Ni, Fe, Cr, V, and Al (Lengauer and Scagnetto, 2018, Solid State Phenomena, 274, 53-100, doi: 10.4028 / www.scientific.net / SSP.274.53).

[0031] The properties of TiC / Ni cermet systems containing significant amounts of metal binders have also been described in other publications (Liu et al., 2005, Journal of Wuhan University of Technology-Mater. Sci.Ed, 20, 35-39, doi: 10.1007 / BF02835022, and Liu and Liu, 2010, Advanced Materials Research, 177, 378-381, doi: 10.4028 / www.scientific.net / AMR.177.378).

[0032] Zhou et al. also reported the effects of Mo and Mo2C on the microstructure and properties of Ti(C,N)-based cermets containing metal binders. The results showed that a Mo2C content of less than 5 wt.% was beneficial to the microstructure and mechanical properties of the cermets, but the effect on the production of coatings for braking systems was not investigated (Zhou, 2009, International Journal of Refractory Metals & Hard Materials, 27, 26-32, doi: 10.1016 / j.ijrmhm.2008.01.011).

[0033] All described prior art cermet powders require the addition of significant amounts of metal binders and / or sintering to produce wear- and corrosion-resistant coatings. However, the presence of metal binders further contributes to particulate emissions during braking.

[0034] Zhang et al. described the effect of molybdenum on the microstructure of iron-based composite laser cladding coatings. They noted that once FeMo... 70 When the addition of more than 9 wt.%, cracks were found in the coating.

[0035] Further prior art is disclosed in Zhang Hao et al., Int. J. Adv. Manuf. Tech., 120(1-2), 2022, 1265-1280; Spranger F et al., Appl. Surf. Science 467, 2018, 493-504; Cutard T. “Microstructure and mechanical properties of Ti(CN)-M2C-(Ni,Co) cermets, XP093146799, 1997, https: / / hal.science / hal-01847836 / document ; US 5,682,595 A; US 2009 / 121197 A1, CN 111 203 670 A; Techel A. etal, J. Therm. Spray Tech. 16 (3) 2007, 374-380; Pejakovic V et al., Materialsand Design 207, 2021, p-109847; and DE 10 2023 118027. Summary of the Invention

[0036] The purpose of this invention is to overcome the shortcomings of existing powders and methods in order to produce crack-free, wear-resistant and corrosion-resistant coatings.

[0037] The objective of this invention is achieved by the ceramic powder according to claim 1.

[0038] The object of the present invention is particularly achieved by a ceramic powder suitable for producing wear-resistant and corrosion-resistant layers, the ceramic powder comprising: a) a mixture of a first component and a second component,

[0039] The first component is selected from Ti carbides, carbonitrides, and nitrides, and mixtures thereof, and

[0040] The second component is selected from carbides, carbonitrides, and nitrides of Mo, W, V, and Nb, and mixtures thereof; and

[0041] Organic adhesives;

[0042] The total amount of the first and second components is at least 60 wt.%, preferably 70 wt.% to 99 wt.%.

[0043] The weight ratio of the first component to the second component is between 70:30 and 98:2, and

[0044] The content of metal binder in the powder is at most 5 wt.%.

[0045] The ceramic powder of the present invention may comprise: b) a solid solution consisting of Ti, a second metal M selected from Mo, W, V, Nb and mixtures thereof, and a nonmetal selected from C, N and mixtures thereof, wherein in b) the weight ratio of Ti to the second metal is 70:30 to 98:2; an organic binder, and the content of the metal binder in the powder is at most 5 wt.%.

[0046] The ceramic powder of the present invention may further comprise: c) a) and b); an organic binder, wherein the content of the metal binder in the powder is at most 5 wt.%.

[0047] The ceramic powder of the present invention is particularly useful as a component in mixtures used together with stainless steel powder to produce wear-resistant and corrosion-resistant layers, especially coatings.

[0048] Another aspect of the invention relates to a wear-resistant and corrosion-resistant layer obtained by treating a surface with a mixture as defined herein.

[0049] Another aspect involves brake discs that include the layer defined herein as a top coating.

[0050] Another aspect of the invention relates to a method for producing ceramic powder as defined herein. Attached Figure Description

[0051] Figure 1 The cross-section of a crack-free topcoat containing a mixture of TiC and Mo2C with a 316L stainless steel matrix after laser cladding is shown. The carbide content of the coating is at least 40 vol.%.

[0052] Figure 2 The cross-section of a crack-free topcoat containing TiCN and Mo2C mixed with a 316L stainless steel matrix after laser cladding is shown. The carbide content of the coating is at least 55 vol.%.

[0053] Figure 3 The cross-section of a crack-free topcoat containing TiCN and Mo2C mixed with a 430L stainless steel matrix after laser cladding is shown. The carbide content of the coating is at least 30 vol.%.

[0054] Figure 4 The cross-section of the cracked top coating, consisting of a mixture of TiC and 316L stainless steel matrix, is shown after laser cladding. The carbide content of the coating is approximately 30 vol.%.

[0055] Figure 5 The cross-section of a crack-free topcoat, formed by laser cladding of a carbonitride solid solution comprising Ti0.95Mo0.05CN 50 / 50 with a 1.3820 stainless steel matrix, is shown. The carbonitride solid solution content in the coating is approximately 49 vol.%. Detailed Implementation

[0056] Surprisingly, the ceramic powder according to the invention has been found to be suitable for producing a stress-free and crack-free protective layer with a high content of carbides or similar hard components, free from crack formation, and with high resistance to mechanical stress.

[0057] The ceramic powder according to the invention contains up to 5 wt.% of a metal binder. Most preferably, the ceramic powder is substantially free of metal binders, in contrast to prior art cermet powders used in coating applications, which contain significant amounts of metal binders, such as nickel, cobalt, iron, copper, silver, chromium, zirconium, silicon, vanadium, and combinations thereof. The term "substantially free of metal binders" should be understood to include powders that may contain metallic impurities, but the impurity content will not bind the non-metallic components, for example, up to 1.5 wt.%.

[0058] It has been found that using organic binders instead of metal binders in ceramic powders surprisingly results in powders with the desired properties, requiring only a limited amount of metal binder or even none at all.

[0059] The layer obtained by this invention exhibits highly desirable performance to improve abrasion resistance and component life during braking.

[0060] The mixture of ceramic powders a) is characterized in that the weight ratio of the first component to the second component is preferably 80:20 to 98:2, more preferably 85:15 to 95:5. The mixture of ceramic powders b) is characterized in that the weight ratio of Ti to the second metal M is 80:20 to 98:2, more preferably 85:15 to 95:5.

[0061] It has been found that the ceramic powder of the present invention (preferably free of metal binders but containing organic binders) is very useful as a component for forming a wear-resistant and corrosion-resistant layer with a high carbide / carbonitride / nitride content.

[0062] Preferably, in mixture a), the first component and the second component are carbides and / or carbonitrides.

[0063] However, in the following text, the term "carbide" also refers to other possible non-metallic parts of the components used, namely carbonitrides, nitrides, etc.

[0064] Preferably, solid solution b) is a carbonitride solid solution.

[0065] Generally, the term "solid solution" refers to a single homogeneous phase formed from Ti, a second metal M, and nonmetals C and / or N. Therefore, particles formed from said solid solutions have a substantially homogeneous composition across their entire cross-section.

[0066] Solid solutions of Ti, the second metal M, and C and / or N can be produced via carbothermal synthesis in a manner known per se, either by reacting Ti in metallic form with the second metal M in metallic form, or by reacting an oxide of Ti with an oxide of M, or by having one of the two metals in metallic form and the other in oxide form, and reacting with a carbon source in a nitrogen-containing atmosphere.

[0067] Preferably, the mixture a) of the ceramic powder of the present invention is characterized in that it comprises Ti carbides and / or carbonitrides as a first component and Mo carbides as a second component. The Mo carbides are preferably Mo2C. Surprisingly, the combination of titanium carbide and / or carbonitride (TiC and / or TiCN) hard phase aggregates with Mo2C has shown exceptionally good results in the production of wear-resistant and corrosion-resistant coatings.

[0068] Furthermore, the second metal M in solid solution b) is preferably Mo. Preferably, solid solution b) is a carbonitride solid solution of (Ti,Mo)(C,N).

[0069] It has been found that when converting the ceramic powder of the present invention into a layer (e.g., by laser cladding), Mo2C appears to hinder the dissolution of the first component or the carbide phase of the first component into the metal matrix due to the additional carbides in the ceramic powder. Therefore, using ceramic powders containing TiCN and / or TiC and Mo2C, crack-free, wear-resistant, and abrasion-resistant laser cladding topcoat with a carbide content of at least 30 vol.% and even up to 60 vol.% can be obtained. Furthermore, the MPU can be reduced due to the high carbide content.

[0070] Similarly, in solid solutions containing Ti and a second metal M (especially Mo), a very high content of hard phases (e.g., carbonitride phases) can be observed in the resulting laser cladding layer without the formation of cracks.

[0071] In a preferred embodiment of the invention, the ceramic powder is characterized in that the organic binder is selected from polyvinyl alcohol, cellulose-based binders, and mixtures thereof. Preferably, the organic binder is a polyvinyl alcohol binder.

[0072] As will be further explained below, the ceramic powder of the present invention can be produced by a method including the step of spray drying a mixture of a first component, a second component, and an organic binder. Preferably, the ceramic powder of the present invention is unsintered.

[0073] The organic binder is soluble in water or an organic solvent. Preferably, the organic binder is a water-soluble polymer that forms a network during spray drying, thereby binding together other components of the ceramic powder. Alternatively, the organic binder may be at least one polymerizable monomer that can be polymerized during spray drying.

[0074] The amount of organic binder in ceramic powder can be from 0.01 to 10 wt.%, for example, 1 to 5 wt.%.

[0075] The ceramic powder of the present invention may contain at least 80 wt.% (e.g., at least 90 wt.% or at least 95 wt.%) of a mixture a), a solid solution b), or a mixture c).

[0076] In addition to mixture a), solid solution b), or mixture c), the ceramic powder of the present invention may also contain other hard components selected from metal carbides, metal carbonitrides, or metal nitrides other than those specified for mixture a).

[0077] The ceramic powder of the present invention can be used as a component in a mixture for producing a wear-resistant and corrosion-resistant layer, wherein the mixture contains stainless steel powder, and wherein the content of the ceramic powder in the mixture is less than 50 wt.%.

[0078] In a preferred embodiment of the invention, the amount of the ceramic powder of the present invention in the mixture is 5 to 30 wt.%, preferably 10 to 25 wt.%. It appears that saturation is reached when the weight ratio is 25 wt.% or higher, which means that the carbide content (vol.%) in the layer formed by the powder mixture cannot be further increased by increasing the weight ratio of the ceramic powder of the present invention in the mixture with stainless steel powder.

[0079] The mixture preferably contains at least 95 wt.%, and most preferably at least 99 wt.%, of ceramic powder and stainless steel powder.

[0080] In a further preferred embodiment, the mixture is essentially composed of the ceramic powder and the stainless steel powder.

[0081] Stainless steel powder can be selected from FeCrMn steel, duplex stainless steel, 430 stainless steel and 316 stainless steel as named according to AISI / SAE stainless steel.

[0082] Preferably, the layer formed is a coating.

[0083] According to another preferred embodiment of the invention, the layer is a top coating for the brake disc.

[0084] A mixture of ceramic powder and stainless steel powder can be applied to a surface by cladding.

[0085] As used herein, the term "cladding" refers to a process of covering or laminating a structural surface to improve, for example, durability. Cladding can include thermal spray cladding or laser cladding. Thermal spray cladding encompasses a variety of processes, such as cold spray cladding, which uses gas or electricity to generate a flame to melt filament or powder material and apply it to a substrate. In cold spray cladding, solid powder is accelerated to speeds up to 1200 m / s in a supersonic gas jet. During contact with the substrate, the particles undergo plastic deformation and adhere to the surface.

[0086] Preferably, the process is laser cladding. "Laser cladding" refers to a manufacturing process that uses a laser beam as a heat source to deposit metallic material onto a surface. The material is melted, fused to the surface, and then typically becomes harder and more wear-resistant than the substrate.

[0087] In the case of laser cladding, the mixture of ceramic powder and stainless steel powder can be prepared before (especially immediately before) the laser beam is fed into it, or prepared in situ by feeding the two powders separately into the laser beam, after which the mixture is formed and melted.

[0088] Preferably, the layer is treated with high-speed laser cladding. High-speed laser cladding, also known as ultra-high-speed laser cladding (EHLA) or ultra-high-speed laser cladding (UHSLC), refers to a laser surface treatment technology with cladding speeds greater than 20 m / min and up to 400 m / min, depending on the properties of the powder and substrate. High-speed laser cladding can serve as an economical and feasible alternative to thermal spraying technology for corrosion and abrasion protection.

[0089] The typical process parameter range for high-speed laser cladding is as follows:

[0090] Laser power: 6 – 22 kW

[0091] Powder mixture feed rate: 100 – 250 g / min

[0092] Cladding speed: 40 – 400 m / min

[0093] Protective gas flow rate: 20 – 50 l / min

[0094] Carbide feed: 10 – 30 wt.%

[0095] Carrier gas flow rate: 1 – 6 l / min

[0096] Powder nozzle diameter: 1.5 – 2.5 mm

[0097] Working distance: 25 mm

[0098] Angle between nozzle and surface: 0° – 25°

[0099] Another aspect of the invention relates to a wear-resistant and corrosion-resistant layer, which can be obtained by treating a surface with a mixture of the ceramic powder of the invention and the stainless steel powder as described above.

[0100] The layer according to the invention can be obtained, in particular, by laser cladding of the surface.

[0101] Preferably, the laser cladding layer has a content of at least 30 vol.%, preferably 40 to 60 vol.%, of a mixture a), or a solid solution b), or a mixture c).

[0102] On the other hand, if the surface is treated by thermal spraying cladding, the maximum content of mixture a), or solid solution b), or mixture c) in the resulting layer can be about 80 vol.%.

[0103] It has been found that a crack-free topcoat can be obtained using a layer content of at least 30 vol.% (or even higher) of mixture a), or solid solution b), or mixture c). The layer obtained according to the invention exhibits high fracture toughness and thermal conductivity, and is able to dissipate forces and temperatures acting upon it without cracking.

[0104] Carbide content can be measured using optical measurements and digital analysis, as further described below.

[0105] According to another preferred embodiment of the invention, the layer is a top coating.

[0106] The obtained top coating is virtually free of cracks.

[0107] In one particular implementation, the top coating is the top coating of the brake disc.

[0108] The ceramic powder of the present invention can also be used in applications other than passenger car brake disc coatings, including as an admixture for brake disc coatings of trucks, trains or engineering vehicles.

[0109] The ceramic powder of the present invention can be produced by the following steps: i) mixing a mixture a), or a solid solution b), or a mixture c) with at least one organic binder and optionally a metallic binder, ii) spray drying the mixture, and iii) optionally sintering the spray-dried mixture.

[0110] Spray drying is important for forming agglomerates by binding the components together. Compared to, for example, cermets, there is no need to sinter the mixture of the two components and the organic binder. Optionally, the spray-dried mixture can also be sintered. Preferably, the spray-dried mixture is not sintered. Therefore, preferably, the powder of the present invention is unsintered.

[0111] Preferably, the spray-dried ceramic powder is flowable and has a low micron-scale particle size distribution for further use in cladding, preferably in laser cladding.

[0112] Spray-dried ceramic powders can have d 10 Particle size distribution less than 30 µm, preferably between 10 and 25 µm.

[0113] Spray-dried ceramic powders can have d 50 Particle size distribution less than 60 µm, preferably between 20 and 50 µm.

[0114] As used in this article, the term "particle size" refers to the d value determined based on the particle size distribution. 10 Value. d 50The value is referred to as the median diameter or median of the granularity distribution, and it is determined based on either a volume-based or quantity-based representation. In this application, all dx values ​​refer to a volume-based representation, i.e., the granularity at “x” vol.% in the cumulative distribution (e.g., dx). 10 A value of 100 µm means that 10 vol.% of the particles have a diameter of less than 100 µm.

[0115] In this invention, particle size distribution (PSD) is determined using laser diffraction particle analysis, preferably using a Microtrac particle analyzer. The particle size of the samples described herein was measured using a Microtrac S3550 particle analyzer in dry mode.

[0116] Particle size measurements were performed using powder samples ranging from 3 to 6 mL (0.125–0.25 US teaspoons). The sample was placed on the storage plate of the Turbotrac disperser. The process was automated using the Microtrac S3550's automatic sequence control. The device was set to "High Shear," level 9–10, purge pressure 0.01 MPa, and particle size analysis mode absorption. The Microtrac S3550 measured PSD from 0.24 µm to 1408 µm in dry mode.

[0117] The PSD of ceramic powder is preferably measured after spray drying.

[0118] The flowability of spray-dried ceramic powder can be between 40s / 50g and 70s / 50g, preferably between 50s / 50g and 60s / 50g.

[0119] "Flowability" refers to the time required for 50 grams of powder to flow through the Hall effect flowmeter funnel. Flowability can be measured as described below.

[0120] The ceramic powders defined in this article can be produced by mixing organic binders at a total weight ratio of 0.01 to 10 wt.%.

[0121] Organic binders can be selected from polyvinyl alcohol, cellulose-based binders, and mixtures thereof.

[0122] Example

[0123] Example 1: TiC + Mo2C

[0124] Titanium carbide powder is supplied (Treibacher Industrie AG, Austria). This powder is obtained through carbothermal synthesis, with a particle size of 1.1 to 2.0 µm and a total carbon content of 19.0 to 20.0 wt.%, corresponding to impurity contents (wt.%) of less than 0.01, 0.6, 0.2, 0.5, 1, and 0.03 for sulfur, oxygen, nitrogen, free carbon, tungsten, and other metallic impurities, respectively. Titanium content is the balance.

[0125] Molybdenum carbide (Mo2C) powder is available (Treibacher Industrie AG, Austria). This powder is obtained through carbothermal synthesis, with a particle size of 1.0 to 2.0 µm and a carbon content of 5.7 to 6.0 wt.%, corresponding to impurity contents (wt.%) of less than 0.05, 0.5, 0.3, and 0.01 for sulfur, oxygen, free carbon, and other metallic impurities, respectively. Molybdenum content is on the balance.

[0126] Particle size was measured using a Fisher Sub-Sieve-Sizer (FSSS). Total carbon, free carbon, and sulfur content were measured using carrier gas thermal extraction (LECO, C / S-Analysator CS-744_2). Oxygen content was measured using carrier gas thermal extraction (LECO, O / N-Analysator TC 500 C). After complete acid dissolution, impurity content was measured using ICP OES (ICPOED 5110DV Agilent).

[0127] The first step involved homogenizing 2 wt.% of an organic polyvinyl alcohol binder (Optapix PAF46; Zschimmer und Schwarz GmbH & Co K, Germany) and 0.03 wt.% of a wetting agent (Glydol N109; from Zschimmer und Schwarz GmbH & Co KG, Germany) with deionized water relative to the total carbide content.

[0128] The raw materials are added to the mixture to obtain a solids content of 65 to 67 wt.% in the slurry, with carbide shares of 95 wt.% for titanium carbide and 5 wt.% for molybdenum carbide. After the carbide addition is complete, the slurry is further homogenized for 25 to 35 minutes. The stirring step is carried out at a variable speed of 400 to 800 rpm to avoid foam formation.

[0129] After homogenization, the slurry was spray-dried in a Vettertec spray dryer. The following spray parameters were set: inlet and outlet air temperatures of 280°C and 115°C, respectively; atomizing wheel speed of 14,000 rpm; and fan speed of 27%. The spray-dried ceramic powder exhibited an average particle size of 50 µm.50 It exhibits good flowability at 50s / 50g. Analysis was performed using PSD measurement (Microtrac S3550 dry method), SEM, and Hall flowability measurement.

[0130] Example 2: TiCN + Mo2C

[0131] Titanium carbonitride powder is available (Treibacher Industrie AG, Austria). This powder is obtained through carbothermal synthesis, with a particle size of 0.9–2.1 µm, a total carbon content of 9.9–11.1 wt.%, a total nitrogen content of 10.3–11.5 wt.%, and impurity contents (wt.%) of sulfur, oxygen, free carbon, iron, and other metallic impurities below 0.01, 0.6, 0.7, 0.45, and 0.03, respectively. Titanium content is the balance.

[0132] Molybdenum carbide (Mo2C) powder is available (Treibacher Industrie AG, Austria). This powder is obtained through carbothermal synthesis, with a particle size of 1.0 to 2.0 µm and a carbon content of 5.7 to 6.0 wt.%, corresponding to impurity contents (wt.%) of less than 0.05, 0.5, 0.3, and 0.01 for sulfur, oxygen, free carbon, and other metallic impurities, respectively. Molybdenum content is on the balance.

[0133] The ceramic powder was obtained using the same method as described in Example 1. The spray-dried ceramic powder exhibited an average particle size of 39 µm. 50 It exhibits good flowability of 51 to 54 s / 50 g. Analysis was performed using PSD measurements (Microtrac S3550 dry method), SEM, and Hall flowability measurements.

[0134] Example 3 – Carbonitride solid solution of Ti0.95Mo0.05CN 50 / 50

[0135] A titanium-molybdenum carbonitride solid solution is provided (Treibacher Industrie AG, Austria). This powder is obtained via a one-step carbothermal synthesis, starting from TiO2 and metallic Mo, along with carbon, at temperatures above 1800°C in a nitrogen atmosphere. The powder has a particle size of 1.8 µm, with titanium and molybdenum contents of 74.9 wt.% and 3.9 wt.%, respectively, a total carbon content of 10.4 wt.%, a total nitrogen content of 10.4 wt.%, and a total impurity content (wt.%) of 0.4 (oxygen, tungsten, and other impurities).

[0136] Particle size was measured using a Fisher Sub-Sieve-Sizer (FSSS). Total carbon, free carbon, and sulfur content were measured using carrier gas thermal extraction (LECO, C / S-Analysator CS-744_2). Oxygen and nitrogen content were measured using carrier gas thermal extraction (LECO, O / N-Analysator TC 500 C). After complete acid dissolution, impurity content was measured using ICP OES (ICPOED 5110DVAgilent).

[0137] The first step involves homogenizing 2 wt.% of an organic polyvinyl alcohol binder (Optapix PAF 46; Zschimmer und Schwarz GmbH & Co K, Germany) and 0.03 wt.% of a wetting agent (Glydol N109; from Zschimmer und Schwarz GmbH & Co KG, Germany) with deionized water relative to the total carbonitride solid solution content.

[0138] A carbonitride solid solution is added to the mixture to obtain a solids content of 65 to 67 wt.% in the slurry. After the addition is complete, the slurry is further homogenized for 25 to 35 minutes. The stirring step is carried out at a variable speed of 400 to 800 rpm to avoid foam formation.

[0139] After homogenization, the slurry was spray-dried in a Vettertec spray dryer. The following spray parameters were set: inlet and outlet air temperatures of 280°C and 115°C, respectively; atomizing wheel speed of 14,000 rpm; and fan speed of 27%. The spray-dried ceramic powder exhibited an average particle size d50 of 41.1 µm and good flowability of 48 s / 50 g. Analysis was performed using PSD measurements (Microtrac S3550 dry method), SEM, and Hall effect flowability measurements.

[0140] Examples 4-9

[0141] In Examples 4 to 9, TiCN + Mo2C powder was produced according to the method of Example 2, wherein the Ti:Mo ratio and the C:N ratio in the TiCN used were different, as follows:

[0142] Example 4: 97 wt.% TiCN (C:N=50:50 wt.%) – 3 wt.% Mo2C

[0143] Example 5: 92 wt.% TiCN (C:N=50:50 wt.%) – 8 wt.% Mo2C

[0144] Example 6: 90 wt.% TiCN (C:N=50:50 wt.%) – 10 wt.% Mo2C

[0145] Example 7: 95 wt.% TiCN (C:N=30:70 wt.%) – 5 wt.% Mo2C

[0146] Example 8: 95 wt.% TiCN (C:N=70:30 wt.%) – 5 wt.% Mo2C

[0147] Example 9: 95 wt.% TiCN (C:N=10:90 wt.%) – 5 wt.% Mo2C

[0148] The average particle size and flowability of each powder are summarized in the table below:

[0149] Table 1:

[0150]

[0151] Comparative Example 1: TiC

[0152] Titanium carbide powder is supplied (Treibacher Industrie AG, Austria). This powder is obtained through carbothermal synthesis, with a particle size of 1.1 to 2.0 µm and a total carbon content of 19.0 to 20.0 wt.%, corresponding to impurity contents (wt.%) of less than 0.01, 0.6, 0.2, 0.5, 1, and 0.03 for sulfur, oxygen, nitrogen, free carbon, tungsten, and other metallic impurities, respectively. Titanium content is the balance.

[0153] The ceramic powder was obtained using the same method as described in Example 1, wherein the carbide content of titanium carbide was 100 wt.%.

[0154] The spray-dried powder showed an average particle size of 40 µm. 50 It exhibits good flowability of 64s / 50g. Analysis was performed using PSD measurements (Microtrac S3550 dry method), SEM, and Hall flowability measurements.

[0155] Comparative Example 2: TiC / FeCr

[0156] A commercially available powder containing a 70 / 30 mixture of TiC and FeCr (GTV Verschleißschutz GmbH, 81.61.8S) and no other components was used. The spray-dried powder showed an average particle size of 42.19 µm. 50It exhibits good flowability of 53s / 50g. Analysis was performed using PSD measurements (Microtrac S3550 dry method), SEM, and Hall effect flowability measurements.

[0157] Production of top coating

[0158] The tests were conducted on a gray cast iron substrate. A top coating was clad using a Laserline LDF 7000-40 diode laser. Powders from the examples and comparative examples, as well as stainless steel powder, were injected separately from a gravimetric powder feed system and mixed in the powder focus above the laser's focal point.

[0159] Inject the following powder mixture:

[0160] Table 2: Powder Mixture Formulation

[0161]

[0162] Laser cladding is performed under the following parameters:

[0163] Laser power: 22 kW

[0164] Powder mixture feed rate: 210 g / min

[0165] cladding speed: 150 m / min

[0166] Protective gas flow rate: 20 – 50 l / min (100% argon)

[0167] Carrier gas flow rate: 3 l / min

[0168] Powder nozzle diameter: 1.75 mm

[0169] Working distance: 25 mm

[0170] Angle between nozzle and surface: 0°

[0171] Characterization of top coating

[0172] The total carbide content of the top coating was determined using a Keyence digital microscope VHX-7000.

[0173] Three topcoat layers were provided for each cladding powder mixture for analysis. Samples were polished at 300 rpm for 3 minutes at a time with progressively finer sandpaper (QATMP80 - P320 – P800 – P1200), followed by manual polishing with P2500 sandpaper in a direction parallel to the layers, and finally fine polished with 3 µm and 1 µm ATM diamond suspensions. Bright-field images were captured at 500x magnification for each sample. The total carbide content was determined using the automatic area measurement (particle size) module of the Keyence digital microscope VHX-7000 image analysis system (VHX 7000N3.0.34.332 system version 1.01) with the following settings:

[0174] Lighting: Coaxial 127

[0175] Brightness: Automatic 80

[0176] Gain: 0dB (preset)

[0177] White balance: Manual R 1.75, G 1.01, B 3.60

[0178] Blur the image using HDR mode, setting brightness to 40, texture to 75, contrast to 60, hue to 50, and depth of field / 3D.

[0179] In the “Area Measurement (Automatic)” module, select the “Brightness (Normal)” extraction method.

[0180] By selecting the mode: "Remove Uneven Brightness (Weak) + Remove Slight Noise While Preserving Shape", and selecting "Extract by Brightness": 5-10, the color threshold of the image can be adjusted accordingly.

[0181] Carbides / carbonitrides / solid solutions are displayed as dark areas. The area percentage of carbides is determined and automatic statistics are generated.

[0182] result

[0183] The top coating obtained by laser cladding the mixture 1 according to the invention onto a gray cast iron substrate surprisingly exhibits a carbide content of at least 40 vol.%, and no cracks form after cladding, such as... Figure 1 As shown.

[0184] Furthermore, according to the cladding mixtures 2 and 3 of the present invention, crack-free topcoats with carbide contents of at least 55 vol.% and at least 30 vol.% are produced, respectively, as shown in the figures below. Figure 2 and Figure 3 As shown.

[0185] Figure 4A top coating is shown, prepared by cladding TiC powder (mixture 4) onto a gray cast iron substrate. Mixture 4 was deposited onto the substrate under the same conditions as cladding mixtures 1 to 3. A carbide content of approximately 30 vol.% was determined, and the coating cracked after cladding.

[0186] The top coating obtained by laser cladding mixture 5 did not show visible cracks, but the carbide content was significantly lower than 30 vol.%.

[0187] Figure 5 The top coating is shown as a result of cladding mixture 6 (Example 3) onto gray cast iron as described above. The top coating shows a (Ti / Mo)(C / N) solid solution content of 49 vol.%, but no cracks were observed after cladding.

[0188] The results clearly demonstrate the superior performance of the topcoats obtained by laser cladding according to mixtures 1, 2, 3, and 6 of the present invention in terms of carbide content and crack formation after cladding. In particular, the topcoats clad using mixtures 1, 2, 3, and 6 exhibited a carbide content of at least 30 vol.% and significantly higher (based on total coating volume), and showed no cracks, meaning the number of cracks in the topcoat was zero. In contrast, the topcoats based on mixtures 4 and 5 either showed crack formation or exhibited lower carbide content.

[0189] Similar results were obtained using mixtures 7 to 12 prepared using the powders according to the invention (powder examples 4 to 9). As shown in Table 3 below, crack-free topcoats with a carbide (carbonitride) content of at least 30 vol.% were obtained:

[0190] Table 3 – Topcoat obtained from mixtures 7 to 12

[0191]

[0192] Wear test

[0193] Brake discs with a top layer produced using powders according to the invention (e.g., TiCN50 / 50+5Mo2C, TiCN30 / 70, Ti0.95Mo0.05CN 50 / 50) combined with a steel matrix 1.3820 were compared with brake discs coated with TiCFeCr using prior art from GTVVerschleißschutz GmbH. Tests were conducted on an AKMaster / SAE J2522 system. Braking systems using the layer according to the invention showed a reduction in wear loss of up to 17-22% compared to prior art materials. All tested brake discs with the top layer according to the invention exhibited a smooth, crack-free surface after AKMaster / SAE J2522 testing.

Claims

1. A ceramic powder suitable for producing wear-resistant and corrosion-resistant layers, comprising: a) A mixture of a first component and a second component, wherein the first component is selected from carbides, carbonitrides, nitrides, and mixtures thereof of Ti, and the second component is selected from carbides, carbonitrides, nitrides, and mixtures thereof of Mo, W, V, and Nb, or b) A solid solution comprising Ti, a second metal M selected from Mo, W, V, Nb and mixtures thereof, and a nonmetal selected from C, N and mixtures thereof, or c) A mixture of a) and b) The total amount of a), b), or c) is at least 60 wt.%, preferably 70 wt.% to 99 wt.%. In (a), the weight ratio of the first component to the second component is between 70:30 and 98:

2. In b), the weight ratio of Ti to the second metal M is between 70:30 and 98:

2. Organic adhesives The content of the metal binder in the powder is at most 5 wt.%.

2. The ceramic powder according to claim 1, characterized in that, In a), the weight ratio of the first component to the second component is 80:20 to 98:2, preferably 85:15 to 95:5, and in b), the weight ratio of Ti to the second metal M is 80:20 to 98:2, preferably 85:15 to 95:

5.

3. The ceramic powder according to claim 1 or 2, characterized in that, The powder contains virtually no metallic binder.

4. The ceramic powder according to any one of the preceding claims, characterized in that, The organic binder is selected from polyvinyl alcohol, cellulose-based binders, and mixtures thereof.

5. The ceramic powder according to any one of the preceding claims, characterized in that, The mixture a) comprises Ti carbides and / or carbonitrides as the first component and Mo carbides as the second component.

6. The ceramic powder according to any one of the preceding claims, characterized in that, Solid solution b) is a carbonitride solid solution of (Ti,Mo)(C,N).

7. The ceramic powder according to any one of the preceding claims, characterized in that, The ceramic powder is unsintered.

8. Use of the ceramic powder according to any one of the preceding claims in a mixture for producing a wear-resistant and corrosion-resistant layer, wherein the mixture contains stainless steel powder, and wherein the content of the ceramic powder in the mixture is less than 50 wt.

9. The use according to claim 8, characterized in that, The amount of ceramic powder in the mixture is 5 to 30 wt., preferably 10 to 25 wt.

10. The use according to claim 8 or 9, characterized in that, The mixture contains at least 95 wt.%, preferably at least 99 wt.%, of the ceramic powder and the stainless steel powder, and most preferably consists essentially of the ceramic powder and the stainless steel powder.

11. The use according to any one of claims 8 to 10, characterized in that, The stainless steel powder is selected from FeCrMn steel, duplex stainless steel, 430 stainless steel and 316 stainless steel as named according to AISI / SAE stainless steel.

12. The use according to any one of claims 8 to 11, characterized in that, The mixture is applied to the surface by cladding, particularly laser cladding.

13. A wear-resistant and corrosion-resistant layer that can be obtained by treating a surface with a mixture as defined in any one of claims 8 to 12.

14. The layer according to claim 13, characterized in that, The process is laser cladding.

15. The layer according to claim 13 or 14, wherein the layer has a content of at least 30 vol.%, preferably 40 to 60 vol.%, of a mixture a), or a solid solution b), or a mixture c).

16. The layer according to any one of claims 13 to 15, wherein the layer is a top coating.

17. The layer of claim 16, wherein the top coating is the top coating of the brake disc.

18. A brake disc comprising a layer as a top coating according to any one of claims 13 to 17.

19. A method for producing ceramic powder according to claims 1 to 7, comprising the following steps: i) Mixing the mixture a) or solid solution b) or mixture c) according to claims 1 to 5 with at least one organic binder and optionally a metallic binder. ii) Spray dry the mixture. iii) Optionally, the spray-dried mixture may be sintered.

20. The method according to claim 19, characterized in that, The organic binder is mixed at a total weight ratio of 0.01 to 10 wt.%.

21. The method according to claim 19 or 20, characterized in that, The organic binder is selected from polyvinyl alcohol, cellulose-based binders, and mixtures thereof.

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