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 piston rings for Internal combustion engines for use in engine and vehicle construction, and processes for their manufacture.
• the principle of the piston rings is Particularly advantageous in modern engines, where these are thermally special are heavily used, and the use of coating materials after State of the art is only possible to a limited extent.
• Electroplated hard chrome layers have been the problem for many years Standard wear protection layer for piston rings. These layers connect one high hardness with high wear resistance, they are very good Surface roughness achievable with low friction coefficients.
• the disadvantage is that low thermal load-bearing capacity of the layer, particularly at Inadequate lubrication between the piston ring and the cylinder wall leads to adhesive wear (Burn marks) and fatigue-related wear (peel and polish effect).
• a major disadvantage of the chrome plating process are the expensive system technology complex process monitoring and the enormous pollution of the environment.
• nitrided layers Another technical solution are the nitrided layers. This is an advantage here the improved flank wear protection, since the coating on all surfaces the piston ring takes place, as well as the lack of layer breakouts, since it is here around diffusion layers with a gradient of nitrogen content from the Surface to the base body.
• the most important process variant for nitriding of piston rings is gas nitriding.
• Piston rings manufactured using the nitriding process and the process itself have major disadvantages. Nitrided piston rings can not be made sharp edged without extensive post-processing, what but in certain applications to ensure the oil wiping effect necessary is.
• Another 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 adhesively (burn marks) which can only be additional run-in layers can be eliminated.
• an extremely brittle connection layer (“White layer "), which are removed by a complex additional process step need to be able to apply a running-in layer.
• the procedure itself is also environmentally hazardous in some process variants (salt bath nitriding), in all variants the long process times result in high costs.
• CVD and PVD coatings are because of the thin layer problematic because the adjustment between ring and cylinder is a break-in phase makes necessary. Layers with little wear are already in this Run-in phase removed so that the base material remains unprotected. However, layers with high wear resistance damage the cylinder improperly. Therefore, the application of these methods to run-in layers limited.
• Base material for thermally sprayed layers according to the prior art Molybdenum, which is usually applied by flame spraying. Pure However, molybdenum layers have a high level of fire protection insufficient wear resistance. To improve the train and Adhesive strengths become self-flowing layers (NiCrBSi or CoNiB) Spray material mixed mechanically, e.g. DE 2 032 722 and US 3,690,684 or US 3,378,372. But since the wear properties of these thermally sprayed Layers are still insufficient, in particular, attempts have been made to overcome them Increase the storage of hard materials, such as carbides, in the layer.
• 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 used for coating piston ring running surfaces with a thermal spraying process (arc spraying) cored wires made of Mo or a low melting alloy together with the filling as a layer Composition 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 blends of the Composition 60-85% Mo, 10-30% of a NiCr alloy and 5-20% TiC.
• the Hard material content according to this patent specification 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% one low melting alloy, which is both as a mechanical mixture as well can be used as composite powder.
• Vuoristo P. et al describe in a contribution entitled "Properties of TiC-Ni and (Ti, Mo) C-NiOC coatings sprayed from agglomerated and sintered powders ", thermal spraying Conference, in International DVS-Conference, March 6-8, 1996, Essen, DE, pages 58 to 61, wettable powder from carbides and complete mixed crystals of carbides and nitrides from IV. and V. subgroup or the carbides of VI. Sub-group together with one or more Metals from the iron, nickel and cobalt group. Although the use of other metals like Tungsten is described, the use of molybdenum in the spray coating is not mentioned and especially not the use of this spray coating for piston rings.
• Japanese patent specification 61-23266 describes a piston ring with a plasma-sprayed mechanical mixture of 40-60 mass% Ti (and the rest Co.
• thermal shock resistance piston ring coatings are also of great importance. Layer systems on the basis of thermally sprayed layers based on Mo catfish compared to other layer systems on thermal shock resistance to be improved.
• Piston rings with an inexpensive to manufacture Wear protection layer, which has a high level of fire protection, due to Change in the alloy composition to meet the requirements in the engine can be adjusted and their wear resistance in the tribological system itself behaves optimally, to propose.
• wear-resistant piston rings according to the invention are characterized in that that there is a 50 - 400 ⁇ m on the surface subject to wear, preferably 100 - 300 ⁇ m, thick, can be applied by thermal spraying Layer.
• This layer is characterized by the fact that several cubic Ti and containing C and / or Ti, a second metal and carbon containing Hard material phases and a metallic binder phase are detectable.
• the proof can 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 sprayed samples and other methods. It is distinctive for the coating system according to the invention that it is simple alloying measures, optimally adapted to the operating conditions can be.
• the layers according to the invention indicate a thermal shock test After 400 cycles, piston rings are at least 10 times lower Weight loss as plasma-sprayed Mo-NiCrBSi coatings. Piston rings with the Layers according to the invention surprisingly have one in the engine test 50% less wear on the ring and at the same time 20% less reduced wear on the cylinder barrel wall compared to plasma-sprayed Mo-NiCrBSI coatings.
• a layer system was thus developed, which compared to the state of the art and the common opinion of the professional world is characterized in that it is compared to conventional material developments less wear both on the piston ring and on the cylinder barrel is coming.
• the piston rings are advantageously used applied a layer consisting of a coating powder according to one or several of claims 5 to 9 is generated by a method which the Process group of thermal spraying, such as plasma spraying, High-speed flame spraying or detonation spraying, is to be attributed.
• the the core-shell structure of the cubic that characterizes the coating powder Hard material phases are transferred to the layer and can be detected in it.
• the particular advantage of using this layer system is that the the molybdenum component that ensures fire safety with the others Basic components of the coating system is compatible. Molybdenum can be bound both in the hard material phase and in the binder phase. in the The nitrogen content of the nitrogen-free system is crucial. in the nitrogenous system will regulate the distribution of the Mo content in the Hard material phases and in the binder from the nitrogen content.
• This Compatibility of the molybdenum with the other components and the possibility of Regulation of its levels between hard phase and binder phase also offers the possibility of minimizing the content of this expensive component in the layer to limit and on the other hand an optimum wear resistance of the ring in Set overall system.
• the system is also characterized by a high chemical resistance to many alkalis and acids.
• the process for producing wear-resistant piston rings 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.
• An agglomerated and sintered coating powder of the fraction 20-45 ⁇ m with the phase composition (Ti, Mo) (C, N) -Ni, which consists of 59.6% by mass TiC 0.7 N 0.3 , 12.0% by mass. % Mo 2 C and 28.4 mass% Ni was produced by atmospheric plasma spraying with a PT A 3000 system on piston rings made of gray cast iron.
• 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 a gray cast iron bushing.
• This bushing is heated to 550-600 ° C and then shock-cooled to 50-70 ° C using 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 in a 6-cylinder Passenger car turbo diesel engine after a 10-point test according to Mercedes-Benz tested.
• the cylinder surfaces consisted of gray cast iron.
• Piston rings with a conventional layer of 75% Mo - 25% NiCrBSi as Top rings used while in cylinders 2, 4 and 6 according to the invention Piston rings were used as tap rings.
• the wear values specified here refer to a test time of 200 h without failures. In the test, the Wear levels for both the tread on the rings and for the cylinder areas overflowed by them are determined.
• the mean values related to the Ring or cylinder bore diameters showed compared to the conventional Coating reduced wear on the rings by 50% and one 20% less wear on the cylinder barrels.

Landscapes

• 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)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7807761

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (12)

Family Cites Families (7)

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

Also Published As

Similar Documents

Legal Events