DD294512A5 - METHOD FOR PRODUCING HARD-MATERIAL SURFACES ON SUBSTRATES WITH LOW MATERIAL MELTING TEMPERATURES - Google Patents

Abstract

The invention relates to a method for producing hard metal-like surfaces on substrates with low material melting temperatures, such as aluminum and its alloys, by means of layer application and energy carrier jet treatment. The field of application extends to structural parts made of light metal with Verschleiszschutzflaechen. With the invention, a solid composite of the hard metal layer is to be achieved with the substrate and different carbide types and mixtures can be used. According to the invention, an intermediate layer, in particular of Fe, Ti, Co, Mo or its mixture, is applied by thermal spraying on the substrate surface. Anschlieszend the application of a hard metal layer with a binder metal of preferably Co and / or Ni takes place. Finally, the coated substrate is spot-treated by energy beams. {Surface, hard metal-like; Aluminum; Verschleiszschutzschicht; Layer application; Spraying, thermal; Energy rays, post-treated; Intermediate layer; Carbide layer; Binder metal}

Description

Field of application of the invention

The field of application of the invention extends to wear protection surfaces on light metals, for example for Werkstückzu- and -abführungen (taxiways) on grinding machines, transport devices on packaging machines or thread guide surfaces in textile machinery.

Characteristic of the known state of the art

The production of carbide-like surfaces by thermal spraying on substrates of light metal, ζ. Β. Aluminum and aluminum alloys are known. The peculiarity of the thermal spray combination with regard to the particle fusion in the layer restricts its possible uses for higher specific loads. Improvements in this field are achieved by the energy beam treatment of the sprayed layers by means of laser or electron beam. For sprayed hard metal layers on z. B. Al Mg 5, the difference between the melting temperatures of the cemented carbide of> 2000 ⁰ C and the light metal alloys of about 650 ° Cz to the non-dominance of said high-energy beam application. The substrate material, before a solid phase transformation begins in the layer, becomes molten and penetrates the layer. Through this process, the layer breaks up in places and the base material deposits as a melt droplet on the surface, whereby the melt droplets evaporate or solidify. In order to prevent this surface destruction and also to prevent the wettability of metal carbides in the molten aluminum as well as the settling of the heavier metal carbides in the melting zone and their segregation, is described in EP 0221 276; C23C4 / 18 proposed to make pasty a metal carbide-metal powder mixture in an aqueous solution of polyvinyl alcohol to apply, to dry without porosity and to melt with the laser beam, the metal content of the coated layer. Furthermore, the metal content should be merged with the aluminum surface. To accomplish this, the metal powder admixed with the metal carbide must consist of a silicon-containing metal and another metal which forms an intermetallic solution with the silicon.

The metal carbide content and the Metallkarbidart are limited, they are determined by the density ratio of the intermetallic phase to the metal carbide. The process described remains limited to the use of titanium carbide (density 4.25 g / cm ³ ). For the use of tungsten carbide (density 17.2g / cm ³ or density 15.5g / cm ³ ), as well as multi-carbide systems with tungsten carbide, the application of this method is not suitable.

Object of the invention

The object of the invention is to be achieved on low-melting materials adherent, resilient and highly wear-resistant hard metal layers.

Explanation of the essence of the invention

The invention has for its object to provide a method for producing carbide-like surfaces on substrates with low material melting temperatures by means of layer application and energy carrier beam treatment, in which a foster composite of the hard metal layer enters the substrate and thereby different carbide types and mixtures can be used.

According to the invention this is achieved in that on the substrate surface, an intermediate layer, in particular of Fe, Ti, Co,

Mo or its mixture is applied by thermal spraying with a layer thickness of 0.05 mm to 0.3 mm. '

Subsequently, the application of a hard metal layer in a known manner, wherein the hard metal layer contains a binder of preferably Co and / or Ni. Finally, the coated substrate is treated by energy carrier beams pointwise, advantageously by means of electron beams as a melting grid with two-dimensional beam deflection.

This procedure ensures that the intermediate layer causes both diffusion with the substrate material and with the binding metal of the hard metal layer when heated, in the solid state and in the molten state

Condition mixed with the substrate material and the binder of the hard metal layer gapless. In this case, the aftertreatment parameters by the laser or preferably electron beam are to be chosen so that the thickness of the intermediate layer ensures the stability of the remelting and that as required the Substratoberflächo melted or their melting is prevented. It is not intended to melt the metal carbides in the substrate surface, but to achieve a firm Vorbund the hard metal layer with the substrate on the induced by the heat input material conversion processes in the substrate, in the intermediate and hard metal layer.

The most important for the surface quality of the carbide-like layer is the choice of material for the intermediate layer, as this must take over several functions. Through them, the size of the heat flow into the base material to influence and given the bonding mechanism between carbide and substrate material.

Metal oxide or metal oxide-metal mixtures which most restrict heat flow are not suitable for interlayer formation since these materials have no tendency to enter diffusion and fusion bonds upon energy carrier jet treatment with the metallic substrate or binder of the cemented carbide layer.

Molten metal does not adhere to metal oxides, it comes because of the large surface tension difference to segregation and to a reduction of the layer adhesion, usually associated with the release of the intermediate layer in both phase planes.

Since Co or Ni is most commonly used as binder in hard metal powder mixtures, very good Fe with carbon contents <0.1% is suitable as intermediate layer material for coating Al and Al alloys. This intermediate material is inexpensive to deposit without complications on Al surfaces and begins to bind to one another at a heat input far below the melting temperatures with Al from 360 ⁰ C, with Ni from 620 ° C and Co from 800 ⁰ C by interactions.

The thickness of the intermediate layer also improves the deformation resistance of the layer system, the bearing capacity of the cemented carbide layer becomes larger and can be made smaller in thickness. When choosing the intermediate thickness, the load of jay and size must be assumed.

The size of the heat input by energy carrier beams is to be matched to the thicknesses of the intermediate layer and the hard metal layer. When using the electron beam treatment, the pointwise melting treatment with two-dimensional beam deflection has better suited than the sheet melting. With a dot pitch of 2.7 ± 1 mm, exposure times <0.25 s and beam powers <'kW, partial or large-area treatment of coatings is given.

The electron beam treatment gives the thermally sprayed cemented carbide layers, via the intermediate layer, the required solid bond with the substrate and a higher wear resistance.

embodiment

The invention is explained below with reference to two preferred embodiments. In the accompanying drawings show

Fig. 1: a side view of a coated rolling element

Fig. 2: a plan view of the rolling element

Fig. 3 is a side view of a coated side plate and

Fig. 4: a plan view of the side plate.

The first embodiment according to FIGS. 1 and 2 relates to a guide body of an inlet and outlet track for ball bearing rings on a grinding machine. On the guide body, a curved rolling element 1 made of Al Mg 5 is screwed, which has a length of 220 mm and a width of 40 mm and 5 mm thick. On the rolling element 1, a hard metal-like surface 2 is applied as a rolling surface for the ball bearing rings. The surface 2 has a layer of hard metal layer 3 and an underlying intermediate layer 4. The hard metal-like surface 2 is produced by the following process steps according to the invention:

- Blast the surface with corundum NK 63.

Plasma spraying of the intermediate layer 4 with Fe powder DV 016, particle size 100-160 μm, carbon content 0.09%, 0.1 mm thick,

- Plasma spraying of hard metal layer 3 of WC + Co 80/20, grain size 32 ± 10μΓη, 0.2 mm thick and

- Electron beam treatment with a dot matrix, dot pitch 2.5mm, contact time 0.1-0.15s, beam power 0.35kW. The coated and electron beam treated rolling element 1 can be used without mechanical aftertreatment and has a high wear resistance next to the rolling bearing rings rolling thereon.

The second Ausführunysbeispiel according to Figures 3 and 4 relates to a U-shaped feed of a Außenrifschleifauton: aten. Along the feeder, round bodies are transported up to a weight of 8 kg / piece. The U-shaped feed consists of a base plate and two side plates 1, which are made of an Al alloy with the dimensions 400 mm χ 300 mm χ 18mm. In each side plate 1 slots 5 are incorporated for receiving stop means. On the side plates 1 is ever a hard metal-like surface 2 as a rolling surface with a width of 130mm. The hard metal-like surface 2 has a layer of hard metal layer 3 and an underlying intermediate layer 4. The hard metal-like surface 2 is produced by the following process steps according to the invention:

- blasting of the surface with corundum NK 63,

Plasma spraying of the intermediate layer 4 of Fe powder DV 016, particle size 100-160 μm, layer thickness 0.3 mm,

- Plasma spraying of hard metal layer 3 of a powder of composition 61% WC + 22% TiC + 8% TaC + 9% Co, layer thickness 0.4 mm and

- Electron beam treatment with a dot matrix, dot pitch 1.8mm, exposure time 0.2-0.24s, beam power 0.9kW. Lanzeitversuche have shown that the invention treated side plates have a high wear resistance.

Claims (1)

A method for producing carbide-like surfaces on substrates with low material melting temperatures, such as aluminum and its alloys, by means of layer application and energy carrier jet treatment, characterized in that on the substrate surface an intermediate layer, in particular of Fe, Ti, Co, Mo or its mixture by thermal spraying with a Layer thickness of 0.05mm to 0.3mm is applied, then the application of a hard metal layer in a known manner, wherein the hard metal layer contains a binding metal of preferably Co and / or Ni, and finally the coated substrate by energy carrier radiation pointwise, advantageously by means of electron beams as a melting grid with two-dimensional beam deflection, aftertreated. For this 1 page drawings