Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
  • C23C4/11—Oxides

Definitions

• the invention relates to coating powder based on chemically modified suboxides of titanium with the general formula Ti n . 2 Me 2 0 2n . 1 for use in various coating technologies (such as the different variants of thermal spraying, such as plasma spraying, high-speed flame spraying (HVOF) and detonation spraying, as well as other processes such as laser coating).
• the coating powder according to the invention can be applied to various components by means of the coating processes mentioned.
• the layers are characterized by high electrical conductivity and solid lubricant properties. For these reasons, application possibilities are derived for the components coated with the powder according to the invention as a functional layer for fuel cells, in electrochemical systems, in vehicle construction, mechanical engineering, and other branches of industry.
• Coating powders based on titanium suboxides are described in addition to a detailed description of the prior art in DE 100 00 979 (in order to avoid unnecessary repetitions, reference is only made to this representation here). These powders are characterized in that n in the formula Ti n 0 2n . 1 has a narrow range of n + 2 or narrower and the coating powder particles have a grain size in the range 10-90 ⁇ m. In coating experiments, however, it was found that the layers sprayed from this powder had an oxygen deficiency in comparison to TiO 2 , but a disruptive partial oxidation during the coating process is inevitable.
• planar defects (Magneli phases) typical of the titanium suboxides of the formula Ti n 0 2r could not be transferred to the thermally sprayed layers (Berger L.-M., Thiele S., Nebelung M., Storz 0., Gasthuber H., Spray Powders and Coatings on the Basis of Titanium Suboxides; in: Thermal Spray 2001: New Surfaces for a New Millennium; Proceedings of the International Thermal Spray Conference, 28-30 May 2001, Singapore, Ed .: CCBerndt, KAKhor, EFLugscheider; Materials Park / Ohio: ASM International, 2001, p. 291-300).
• coating powders according to the invention are modified by at least one metallic alloy element, and with the general formula Ti n . 2 Me 2 0 2n _ , can be described.
• the coating powders advantageously contain one or more further alloy elements, the individual phases of the general formula Ti n . 2 Me 2 0 2n . ⁇ stabilize or are inert.
• Titanium suboxides with planar defect structures (Magneli phases with the general formula Ti n 0 2n .,) Can also be described as a homologous series by the formula x Ti0 2 .Ti 2 0 3 .
• they can also be easily synthesized by a solid-state reaction from starting mixtures of different molar ratios of Ti0 2 and Ti 2 0 3 .
• Ti 2 0 3 can be replaced by a large number of other trivalent metal oxides.
• the reaction products have the structure of Magneli phases. These are in particular Cr 2 0 3 and V 2 0 3 .
• modified titanium suboxides with the structure of Magneli phases which are represented by the general formula Ti n . 2 Cr 2 0 2n . 1 can be described, with n> 4 simply produce.
• Pure titanium suboxides with the structure of Magneli phases, which result from the reaction of Ti0 2 and Ti 2 0 3 only form if the reaction is carried out in an inert atmosphere, for example in argon.
• Magneli phases of the structure Ti n are formed . 2 Cr 2 0 2lvl with n> 4 in air.
• phase Ti n . 2 Cr 2 0 2n . 1 with n 3 (TiCr 2 0 5 ) only forms if it is stabilized by further alloying elements, such as aluminum. Further alloying elements can be applied to all phases Ti n . 2 Cr n O 2n . 1 have a stabilizing effect.
• Modified titanium suboxides with the structure of Magneli phases which are represented by the general formula Ti n . 2 V 2 0 2n . 1 can be described with n> 3, for example simply by the processes mentioned in US 5,049,537.
• n> 3 for example simply by the processes mentioned in US 5,049,537.
• the toxicity of V 2 0 3 and vanadium oxides of other valency of the vanadium requires increased precautionary measures in the synthesis of the Magneli phases, the production of the coating powders and their processing by thermal spraying.
• n in the formula Ti n . 2 Me 2 0 2n . 1 comprises a range of n ⁇ 2.
• n ⁇ 5 it is possible that there are only phases in the coating powder which correspond to a discrete value for n. This means that the coating powder is single-phase if only one phase is known for n. If several phases are known for a discrete n, these can exist side by side. Due to the ever smaller differences in the oxygen contents with increasing n the coating powders with n> 5 can be produced such that in addition to the desired phase n there is also a second phase n + 1 or n-1.
• the coating powder has a grain size in the range 10 to 90 ⁇ m.
• the coating powder can also have a grain size range of 10-45 ⁇ m.
• the coating powders according to the invention can have different properties with regard to their porosity and their morphology, and the production can in principle take place in different ways.
• the preferred variant is that the synthesis takes place via a solid-state reaction of homogeneous starting mixtures of finely dispersed titanium dioxide powder and trivalent metal oxide powder, in particular Cr 2 0 3 and V 2 0 3 , of different molar ratios.
• the homogeneous starting mixtures can contain the further alloying elements, for example in the form of oxides.
• metal powder or compounds of the alloy element which decompose to form oxides can also be used.
• an additional reduction with a solid or gaseous reducing agent can take place.
• Finely dispersed powders according to the formula Ti n can be prepared on these different synthetic routes.
• 2 Me 2 0 2n . ⁇ preferably Ti n . 2 Cr 2 0 2n . 1 and Ti n . 2 V 2 0 2n . , which advantageously have a grain size ⁇ 5 ⁇ m.
• the suboxide Ti n . 2 Me 2 0 2n .- optionally prepared by grinding processes and the grain size can be reduced.
• the production of the coating powder from the synthesized powder of the composition Ti n . 2 Me 2 0 2n . 1 is preferably carried out by agglomeration, sintering and fractionation according to the process steps described in DE 100 00 979, without changing the phase composition.
• Spray drying is the preferred method for agglomeration.
• the starting oxides Ti0 2 and Cr 2 0 3 can be spray-dried together in the required ratio and the corresponding Magneli phases in the sintered coating powder are obtained by reaction sintering.
• Another way of manufacturing is to make the final phase composition during the process from previously synthesized powders Adjust the sintering of the coating powder. This is done, for example, by changing the sintering temperature compared to the synthesis temperature.
• the grain size of the primary individual particles does not change or changes only slightly.
• the grain size of the sintered individual particles in the coating powder particles is preferably ⁇ 5 ⁇ m. Usually no more than 15% of the sintered coating powder particles are below the desired particle size range, this value can be greatly reduced if necessary by repeated fractionation.
• these coating powders are advantageously distinguished, inter alia, by a spherical morphology and a porosity greater than 3%, preferably greater than 10%.
• the porosity of the coating powder is determined by mercury porosimetry.
• the intruded volume at a pressure that corresponds to a pore diameter> 1 ⁇ m is not taken into account, since this mercury is pressed into the cavities between the individual coating powder particles. Due to the porosity and the fine individual particles, these coating powders are also characterized by specific surfaces> 1 m / g.
• coating powders Another possibility of producing the coating powders according to the invention is that the synthesis of Ti n . 2 Me 2 0 2n . 1 is directly implemented in the production of coating powder using other processes, such as melting and breaking or sintering and breaking. These coating powders can easily be further reduced with a gaseous reducing agent. The morphology, particle size and particle size distribution of the starting powder are essentially retained. These coating powders can also have a different, for example an angular, morphology and a porosity of ⁇ 10%, preferably ⁇ 5%.
• All coating powders according to the invention can be processed into layers using various surface technologies. They are particularly suitable for the process group of thermal spraying, such as plasma spraying, high-speed flame spraying (HVOF) and detonation spraying, and Coating processes using laser and hybrid processes.
• thermal spraying such as plasma spraying, high-speed flame spraying (HVOF) and detonation spraying, and Coating processes using laser and hybrid processes.
• HVOF high-speed flame spraying
• detonation spraying and Coating processes using laser and hybrid processes.
• Coating processes using laser and hybrid processes In the layers, no or only slight changes in the chemical and phase composition can be detected compared to the coating powder.
• Ti n . 2 Cr 2 0 2n . 1 there are no oxidation processes and thus changes in the chemical and phase composition.
• the structure of the Magneli phases can be transferred from the coating powder into the layer.
• the layers are preferably used as electrically conductive ceramic layers which at the same time have high mechanical wear and corrosion resistance. In addition, they can also be used as solid lubricant and wear protection layers. If the layers are made porous by the choice of suitable coating parameters, they are also suitable for use as electrode layers.
• the coating powder according to the invention is to be described in more detail in the following exemplary embodiment.
• X-ray phase analysis showed that the phase composition of the coating powder has not changed compared to the finely dispersed starting powder.
• the grain size distribution of the coating powder particles was measured with the aid of a laser diffraction device using dry dispersion. The measurement gave the granulometric parameters d 10 of 15 ⁇ m, d 50 of 28 ⁇ m and d 90 of 43 ⁇ m.
• the inner open porosity of the coating powder was determined with the help of mercury porosimetry at 1 1%. When calculating the porosity, the intruded volume at a pressure that corresponds to a pore diameter> 1 ⁇ m was not taken into account, since this mercury is pressed into the cavities between the individual coating powder particles.
• the specific surface area of the powder was 1.55 m 2 / g.
• the coating powder was then applied to atmospheric plasma spraying (APS) using an argon / hydrogen plasma with a power of 42 kW with gas flows of Ar 45 l / min and H 2 10 l / min (each under standard conditions) immediately before spraying steel substrate roughened by sandblasting.
• APS atmospheric plasma spraying
• the spray distance was 1 10 mm and the powder delivery rate was 35 g / min.
• a layer thickness of around 300 ⁇ m was achieved.
• X-ray phase analysis revealed Ti 2 Cr 2 0 7 in the sprayed layer.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Coating By Spraying Or Casting (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)

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• 2001
  • 2001-03-05 DE DE10110448A patent/DE10110448A1/de not_active Withdrawn
• 2002
  • 2002-03-04 JP JP2002577938A patent/JP4421820B2/ja not_active Expired - Fee Related
  • 2002-03-04 WO PCT/EP2002/002323 patent/WO2002079535A2/fr not_active Ceased
  • 2002-03-04 AT AT02740417T patent/ATE364733T1/de active
  • 2002-03-04 EP EP02740417A patent/EP1379708B1/fr not_active Expired - Lifetime
  • 2002-03-04 US US10/469,935 patent/US7445763B2/en not_active Expired - Fee Related
  • 2002-03-04 DE DE10291362T patent/DE10291362D2/de not_active Expired - Lifetime
  • 2002-03-04 DE DE50210318T patent/DE50210318D1/de not_active Expired - Lifetime

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