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
  • C23C4/06—Metallic material

Definitions

• the invention relates to wear-resistant coated components for internal combustion engines, in particular piston rings, for use in engine and vehicle construction, and to methods for their production.
• the use of the components is particularly advantageous in engines of modern design, where they are particularly thermally stressed and the use of coating materials according to the prior art is only possible to a limited extent.
• Electroplated hard chrome layers have been the standard wear protection layer for piston rings for many years. These layers combine high hardness with high wear resistance, very good surface roughness with low friction coefficients can be achieved.
• a disadvantage is the low thermal load-bearing capacity of the layer, which leads to adhesive wear (burn marks) and fatigue-related wear (peel and polish effect), in particular if there is insufficient lubrication between the piston ring and the cylinder wall.
• a major disadvantage of the chrome plating process are the expensive plant technology, the complex process monitoring and the enormous pollution of the environment.
• nitrided layers Another technical solution is provided by the nitrided layers.
• the improved flank wear protection is advantageous here, since the coating takes place on all surfaces of the piston ring, and the lack of layer breakouts, since these are diffusion layers with a gradient of the nitrogen content from Surface to the base body.
• the most important process variant for nitriding piston rings is gas nitriding.
• Piston rings manufactured using the nitriding process and the process itself have decisive disadvantages.
• Nitrided piston rings cannot be made with sharp edges without extensive post-processing, but this is necessary in certain applications to ensure the oil wiping effect.
• a further disadvantage is the susceptibility to corrosion of the rings and the thermal stress on the substrate during the coating process.
• Nitrided piston rings tend to wear adhesive (traces of fire) which can only be removed by means of additional running-in layers.
• all nitriding processes form an extremely brittle connecting layer ("white layer"), which must be removed by a complex additional process step in order to be able to apply a running-in layer.
• the process itself is also environmentally hazardous in some process variants (salt bath nitriding), in all variants there are high costs due to the long process times.
• CVD and PVD coatings are problematic due to the low layer thickness, since the adjustment between the ring and cylinder requires a running-in phase. Layers with little wear are already removed in this run-in phase, so that the base material remains unprotected. However, layers with high wear resistance damage the cylinder in an inadmissible manner. The application of these methods is therefore limited to run-in layers.
• Coatings that are applied to piston rings by means of various thermal spray processes are characterized by high wear resistance, a high variability of the coating compositions and low costs by the high productivity of the coating process. Due to the variability of the material selection in thermal spraying, the layer material in particular can be adapted extremely well to the load level of the respective motor. Another advantage of coating by thermal spraying is the low thermal load on the substrate. A porosity that fills with lubricant and ensures excellent emergency running properties can be introduced in a targeted manner.
• the base material for thermally sprayed layers according to the prior art is molybdenum, which is usually applied by means of flame spraying. Pure molybdenum layers, however, have an inadequate wear resistance in addition to the high level of fire protection.
• German patent DE 35 15 107 describes wettable powders with the compositions 10-25% Mo, 25-50% Cr 3 C 2 and 55-70% of a low-melting nickel alloy or 25-45% Mo, 50-25% of a hard material such as Molybdenum carbide, chromium carbide Cr 23 C 6 and / or elementary chromium and 45-60% of a low-melting nickel alloy, which can be used both as a mechanical mixture and as a composite powder.
• a hard material such as Molybdenum carbide, chromium carbide Cr 23 C 6 and / or elementary chromium and 45-60% of a low-melting nickel alloy
• the patent DE 38 02 920 uses for the coating of piston ring running surfaces with a thermal spraying process (arc spraying) cored wires made of Mo or a low-melting alloy which together with the filling as a layer a composition of 40-60% Mo, 0-35% of a hard material (hard metals, metal carbides , -carbonitride, or -nitride) and 10-50% of a low-melting alloy.
• arc spraying arc spraying
• U.S. Patent 4,233,072 uses mechanical mixtures of the composition 60-85% Mo, 10-30% of a NiCr alloy and 5-20% TiC.
• the hard material content according to this patent is extremely low.
• German patent DE 32 47 054 describes a wettable powder with the composition 20-60% Mo, 25-50% molybdenum carbide and up to 30% of a low-melting alloy, which can be used both as a mechanical mixture and as a composite powder.
• Japanese patent specification 61-23266 describes a piston ring with a plasma-sprayed mechanical mixture of 40-60% by mass of TiC and the rest of the Co.
• the disadvantage is the use of the mechanical mixture of the two components and the insufficient degree of alloying of the coating.
• piston-piston-ring-cylinder tribological system is considered in its entirety. Extremely wear-resistant layers on piston rings, for example, lead to increased cylinder wear, which negatively affects the function of the overall system. This is evident, for example, from the development of Cr 3 C 2 NiCr layers, which led to increased cylinder wear (H. Fukutome, et al., Proc. Int. Thermal Spray Conf. 1995, Kobe, Ed. By A.Ohmori, High Temperature Society of Japan, 1995, Vol. 1, p.21-26).
• this layer system also for coatings on other surfaces in internal combustion engines, e.g. can be used for coating the cylinder walls.
• wear-resistant components according to the invention are characterized in that a 50-400 ⁇ m, preferably 100-300 ⁇ m, thick layer which can be applied by means of a thermal spraying process.
• This layer is characterized in that several cubic Ti and C-containing and / or Ti, a second metal and carbon-containing hard material phases and a metallic binder phase can be detected.
• the detection can be carried out with common physical examination methods, such as X-ray diffraction analysis, scanning electron microscopic examinations and energy-dispersive X-ray microanalysis (EDX) after metallographic preparation of sprayed samples as well as other methods.
• EDX energy-dispersive X-ray microanalysis
• the layers according to the invention show a loss in mass which is at least a factor of 10 lower than that of plasma-sprayed Mo-NiCrBSi coatings.
• Piston rings with the layers according to the invention surprisingly show a 50% reduction in wear on the ring and at the same time a 20% reduction in wear on the cylinder barrel in comparison to plasma-sprayed Mo-NiCrBSi coatings.
• a layer system was thus developed, which is distinguished from the state of the art and the common opinion of the professional world in that compared to conventional material developments there is less wear both on the piston ring and on the cylinder barrel wall.
• a layer is applied to the components, in particular piston rings, which is produced from a coating powder according to one or more of claims 5 to 9 by means of a process which is attributable to the process group of thermal spraying, such as plasma spraying, high-speed flame spraying or detonation spraying.
• the core-shell structure of the cubic hard material phases that characterizes the coating powder is transferred to the layer and can be detected in the layer.
• the particular advantage of using this layer system is that the molybdenum component that ensures fire safety is compatible with the other basic components of the coating system. Molybdenum can be bound in the hard phase as well as in the binder phase. The carbon content is decisive for this in the nitrogen-free system.
• the regulation of the distribution of the Mo content in the hard material phases and in the binder is taken over by the nitrogen content.
• This compatibility of the molybdenum with the other components and the possibility of regulating its contents between hard material phases and binder phase also offers the possibility to limit the content of this expensive component in the layer to a minimum and, on the other hand, to set an optimum wear resistance of the ring in the overall system.
• the system is also characterized by its high chemical resistance to many alkalis and acids.
• the process for producing wear-resistant components for internal combustion engines is characterized in that in principle all processes which are assigned to the process group of thermal spraying can be used. For cost reasons, atmospheric plasma spraying and high-speed flame spraying (HVOF) are preferred.
• the oxidation of the coating material can be countered by adding carbides such as Cr 3 C 2 to the coating powder, which oxidizes to form metallic chromium, which can advantageously alloy the metallic binder phase.
• the spray distance was 130 mm.
• the piston rings were subjected to a thermal shock test after finishing. 5 piston rings were individually weighed and packaged in one Gray cast iron bushing lined.
• This socket is heated to 550-600 ° C and then cooled to 50-70 ° C with a water jacket.
• the mass loss was measured after every 100 cycles.
• the piston rings with the coating according to the invention had an average loss of mass of 6.9 mg per ring.
• a conventional coating of 75% Mo - 25% NiCrBSi showed an average mass loss of 72.7 mg per ring.
• the performance of the coating according to the invention was tested in a 6-cylinder car turbodiesel engine after a 10-point test according to Mercedes-Benz.
• the cylinder surfaces consisted of gray cast iron.
• Piston rings with a conventional layer of 75% Mo - 25% NiCrBSi were used as top rings in cylinders 1, 3 and 5, while piston rings according to the invention were used as top rings in cylinders 2, 4 and 6.
• the wear values given here refer to a test time of 200 h without failures. During the test, the levels of wear were determined both for the tread coating of the rings and for the cylinder areas overrun by them.
• the mean values based on the ring or cylinder bore diameter showed a 50% reduction in wear on the rings and a 20% reduction in wear on the cylinder barrel walls compared to the conventional coating.

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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)
• Coating By Spraying Or Casting (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (8)

Cited By (8)

Families Citing this family (5)

Citations (5)

Family Cites Families (2)

• 1996
  • 1996-10-02 DE DE19640789A patent/DE19640789C2/de not_active Expired - Fee Related
• 1997
  • 1997-09-25 WO PCT/DE1997/002205 patent/WO1998014628A1/de active IP Right Grant
  • 1997-09-25 JP JP51613198A patent/JP2001503816A/ja active Pending
  • 1997-09-25 ES ES97912019T patent/ES2168618T3/es not_active Expired - Lifetime
  • 1997-09-25 AU AU49402/97A patent/AU4940297A/en not_active Abandoned
  • 1997-09-25 PT PT97912019T patent/PT931172E/pt unknown
  • 1997-09-25 BR BR9711841-9A patent/BR9711841A/pt not_active Application Discontinuation
  • 1997-09-25 DE DE59705801T patent/DE59705801D1/de not_active Expired - Fee Related
  • 1997-09-25 EP EP97912019A patent/EP0931172B1/de not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (3)

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