DE102004038572B4 - Wear resistant coating to protect a surface and method of making the same - Google Patents

Abstract

Wear-resistant coating for Protection of a surface for temperature-stressed Parts of industrial installations, in particular for pipes, tube bundles and / or fin walls in large combustion plants using chromium carbides applied by flame spraying, characterized in that the surface of the protected Plant components with at least a first layer of a chromium carbide-containing Steel and one made of pure aluminum oxidized on the surface Cover layer exists.

Description

The The invention relates to a wear-resistant coating for protecting a surface for temperature-stressed Parts of industrial installations, in particular for pipes, tube bundles and / or finned in large combustion plants using chromium steels sprayed by flame spraying. she is particularly suitable, such protective layers are particularly effective apply. Have produced coatings according to the invention a very good adhesion to the surface to be protected and a high abrasion resistance.

to Finishing the surface of metallic objects It has been around for a while known, metallic or ceramic protective coatings by so-called Flame spraying, thermal plasma spraying or similar Apply procedure.

there the material to be applied is guided by a supply into a flame, thereby melted and cooked at high speed on the previously prepared area spun.

Such a method describes, for example, the EP 341672 B1 , Also in the EP 825272 A2 a corresponding structure is shown.

Another application method, in which the material is guided in a high-heated by an arc of salary and thereby melted, describes the DE 10128565 A1 ,

Around with the application method very special surface properties have already been achieved, various combinations of coating materials proposed.

For a particularly abrasion-resistant surface for highly stressed engine parts, especially piston rings, proposes the DE 10200508 A1 to apply a powdered mixture of nickel-chromium alloys, chromium carbide and molybdenum through an oxygen-fuel mixture at high speed.

Also WO 02/24970 A2 discloses a wear-resistant coating for running surfaces and flanks of piston rings. she beats among other things, that this coating is made of an iron alloy powder and chromium carbide can exist and by means of thermal spraying is applied.

Furthermore is known from US4275124A, the wear behavior of MCrAlY alloys by in-situ formed carbides or by alloyed carbides too increase.

In the regarded as generic DE 19831173 A1 Finally, a method for producing a corrosion-resistant protection for temperature-stressed parts, in particular for pipes, tube bundles and fin walls in large combustion plants proposed in which applied to the temperature-loaded parts wear and corrosion layer using an autogenous flame spraying or arc-wire spraying process becomes. In this process, several partial layers of self-flowing and non-self-flowing materials are sprayed on alternately and then sintered.

there become the self-flowing ones Layers formed by a Ni-Cr-Fe-B-Si alloy.

When alternative method is also proposed in this document, to use the high-speed flame spraying method.

adversely At this procedure is that both for the self-flowing as also for the non-self-flowing Layer of high quality materials must be used. One Another disadvantage arises from the fact that the layers after the Application sintered or melted in another operation Need to become.

at the production of metal coatings for the purpose of corrosion protection and the abrasion protection, the practice shows that it is bad Clamps with the substrate too separation phenomena can come, the layers have too high a porosity and the hardness of the Do not resist layer of abrasion.

It Therefore, the task was to develop a layer, which a high abrasion resistance and wear resistance guaranteed. The object of the invention is therefore in particular, a coating and a method of applying this coating according to the preamble to propose the main claim, the same surface resistance a lower material usage and a high productivity allowed.

According to the invention this Task by a coating produced by flame spraying according to the characteristics solved the main claim. A preferred method for producing such a coating according to the invention is shown in claim 5.

For the formation of an effective protection against abrasion and heat corrosion is according to the invention proposed to cover the surface of the plant parts to be protected at least with a first layer of chromkarbidhaltigem steel and further with a cover layer formed of pure aluminum.

Around the connection between the surface of the system components and the To improve the protective layer to be applied, the invention proposes a wear protection layer with one inside out build up increasing proportion of chromium carbide, by placing between the surface of to be protected plant parts and the cover layer formed of pure aluminum several wear protection layers arranged with different content of chromium and / or chromium carbide become.

When This has proved to be advantageous when the chromium content of layer between 5 and 15% on the parts of the system is in the outer layers increases to levels of 15 to 20%.

ever according to the number of layers to be applied, the invention proposes that strengthens the individual layers between 50 and 800 μm exhibit.

to Production of a wear-resistant coating one goes according to the invention so that on the surface of the Workpiece previously cleaned by mechanical or chemical means, by means of the known wire flame spraying method by spraying a steel alloy with a chromium content between 8 and 15%, preferably 13%, a first primer layer having a layer thickness from 80 to 250 μm, preferably 200 μm, is applied. On this layer will be following the same procedure one or more additional wear protection layers with outward Content of 12 to 20% increasing chromium levels and layer thicknesses between 100 and 600 μm, preferably 200 to 500 μm, applied. Subsequently a seal is made by applying a layer of pure aluminum with an aluminum content of 98 to 99.99% and a layer thickness from 50 to 250 μm, preferably 100 to 200 μm, which also applied by the wire flame spraying method becomes.

The Invention will be explained below with reference to an embodiment.

To the Structure of a protective layer according to the invention is applied to a freshly blasted surface, with a cleanliness of SA 2.5 to 3.0 and grain size 0.5 to 3.0 mm, a wire melted in a wire flame spray gun as a fine dusted Applied particle layer.

in the Under the invention, the known method of "wire flame-spraying" is applied Spraying is a sweat-like process, in which by spraying liquid metal particles on a prepared metal surface a finishing this surface is achieved. The welding wires used for this vary in wire diameter between 2.0 mm to 3.17 mm.

there become solid wires and cored wires (tube wires) used, which are continuously fed into the combustion chamber of the gun.

The used wire flame-spray gun takes over the wire transport, the heating and melting of the wires and the transport of the particles and their acceleration up to supersonic speed.

The Fuel gas mixture consists of acetylene and oxygen or propane and oxygen. As a carrier gas is cleaned and oil-free Pressed air used.

Of the strong impact of the particles on the surface of the workpiece, the achieved by the high speed leads to a high density of coatings. The low residence time in the heating zone of the spray gun minimized the oxidation of the particles at the high spray temperatures. Of the Air pressure accelerates the particles at a spray distance from 200 - 300 mm still liquid until doughy on the metal surface hit where they cool down quickly clamp and thus adhere.

The Wire flame spraying does not affect the physical and chemical properties of the carrier material, since in this case surface temperatures of maximum 150 ° C occur.

structural changes occur only when reaching temperatures above 450 ° C.

The full Layer thickness is a total of about 600 to 800 microns.

These is composed of a metallic adhesive layer, a metallic one Wear protection layer and an aluminum seal.

When Adhesive base is a chrome-steel wire using the well-known "wire-flame-spray-process" sprayed with a chromium content of 10.

Of the Adhesive base has a layer thickness of about 200 microns (mechanical Measurement).

As wear protection layer is after the a chromium-steel wire with a chromium content of 17%.

By continuous, metered addition of carbon during the Spraying is achieved when cooling the applied layer The chromium portion largely deposited as chromium carbide crystals becomes.

The Layer thickness is here about 400 microns (mechanical Measurement).

Finally, it will on the existing of the above two materials coating using the "wire-flame-spray-process", a solid wire of pure aluminum (Al 99.9%) applied as a seal.

The Material of the seal has a layer thickness of about 100 to 200 μm (mechanical measurement).

The so resulting coating has hardnesses of about 700 HV in the Matrix and about 1000-1700 HV in the chromium carbide particles, which are finely distributed in the layer available.

By the use of pure aluminum sealing will be another effect achieved, which is that after the effect of temperature in the operating process in combustion chambers temperatures above 450 ° C aluminum oxidize.

there creates an aluminum oxide, which as a fine ceramic layer the potential Closing pores, and by a smooth, hard layer an additional wear resistance across from generated rubbing wear Has.

This wear protection can be used primarily in combustion chambers used by thermal power plants, and has lifetimes from 25,000-30,000 Operating hours.

To belong to the preferred objects e.g. thermally influenced finned wall pipes, single piping, Support tubes and combustion chamber corners, which additionally a steady abrasion through flowing Ash particles or the like are exposed.

Of the High economic benefit is that under exploitation the well-known "wire flame-spraying method" and use of this Shift a service life increase is achieved.

Thereby Costs are caused by failure and repair, by cutting out and welding would be necessary from new pipes, minimized, thanks to experiments in thermal power plants and waste recycling plants can be occupied.

Farther are unintended damages This layer can be repaired at any time and with little effort on site.

Claims (6)

Wear-resistant coating for protecting a surface for temperature-stressed parts of industrial plants, in particular for pipes, tube bundles and / or fin walls in large combustion plants using chromium carbides applied by flame spraying, characterized in that the surface of the system parts to be protected at least with a first layer of chromkarbidhaltigen Steel and one of pure aluminum formed on the surface oxidized cover layer consists. Wear-resistant coating after Claim 1, characterized in that between the surface of to be protected Plant components and the cover layer formed of pure aluminum several Wear-resistant coatings arranged with different content of chromium and / or chromium carbide are. Wear-resistant coating after Claim 2, characterized in that the chromium content of The layer between 5 and 15% of the plant parts is in the outer layers Content increases from 15 to 20%. Wear-resistant coating after one of the preceding claims , characterized in that the individual layer thicknesses between 50 and 800 μm be. Method for producing a wear-resistant coating according to one of the preceding claims, characterized in that the surface of the workpiece, previously cleaned by mechanical or chemical processes, is produced by means of the known wire flame spraying method using an acetylene-oxygen-nitrogen mixture and with the addition of carbon by spraying an alloyed steel alloy added as an alloyed welding wire with a chromium content of between 8 and 15%, a first primer layer having a layer thickness of 80 to 250 μm is applied to this layer by the same method be applied to contents of 12 to 20% increasing amounts of chromium and layer thicknesses between 100 and 600 microns and then that a cover layer of pure aluminum with an aluminum content of 98 to 99.99% and a layer thickness of 50 to 250 microns after de m wire flame spraying method is applied. Process for producing a wear-resistant coating according to claim 5, characterized in that the alloyed as welding wire should run Steel alloy has a chromium content of 13% that the first Primer layer is applied with a layer thickness of 200 microns, that on this layer applied by the same process wear protection layers Have layer thicknesses between 200 to 500 microns and that subsequently applied Cover layer of pure aluminum has a layer thickness of 100 to 200 microns.