DE2011966A1 - Coating conductors with non-metallic powder applied by electrophoresi - Google Patents

Abstract

In process for applying adherent crack-free hard wear-resistant layers of powdered non-metallic materials, such as carbides, nitrides, borides, silicides and oxides of metals such as W, Mo, Ta, Nb, Ti, Zr; carbides and oxides of Si and B, diamond powder and Al2O3, by electrophoresis on to an electrically conductive support of desired shape, the electrophoretically applied layer is anchored by electrodepositing a metal or metal alloy first on the support and then in the pores of the powder layer. Before start of electrodeposition the pores of the powder layer are kept free from air or gas by means of left over suspension agent of electrophoresis or advantageously by means of electrolyte introduced into the pores by means of a wetting agent or vacuum and if necessary pressure. For applying porous layers, the powdered materials are provided, before electrophoretic separation, with a covering layer, advantageously an organic layer for example a lacquer or paraffin soluble in a solvent, which is removed after electroplating, advantageously by dissolving with a solvent.

Description

Method of applying a firmly adhering layer of non-metallic Substances on an electrically conductive surface In technology, there are many the desire to have electrically conductive, especially metallic substrates with powdery Layers of non-metallic materials, in particular metal compounds, to be covered and to anchor them firmly there. These are - generally metal compounds, they are characterized by high hardness and high wear resistance. Most of them are Substances that are known as basic substances in metal ceramics, such as carbide, nitride, Borides, silicides and oxides of the metals tungsten, molybdenum, tantalum, niobium, titanium, zirconium; Carbides, nitrides and oxides of silicon and boron or also diamond powder and others, e.g. A120D.

A method is known in which such substances on an electrically conductive, horizontal surface applied and then in a copper or Nickel electrolytes are firmly bonded to the base and galvanically connected. That However, the procedure is limited to horizontal documents.

It is also known to have metal compounds in powder form in an electrolyte by stirring to keep them suspended while removing an electrolyte deposit metal to be deposited on a conductive surface. Included but is the amount of metal compounds compared to the amount of electrodeposited Relatively few substances; it increases with a relatively high proportion of metal compounds seldom more than 5% of the volume of the electrolyte Ways to deposit metal oxides, carbides, nitrides and others in powder form on metals. Nan is also able to anneal and roll on these substances after coating ii to connect with the raw material. But the splints formed in this way are often cracked and therefore useless. In addition, the annealing and rolling require a high Expenditure of resources and energy.

In contrast, the object of the invention consists in the method to develop crack-free on electrically conductive substrates of any S'orm and evenly firmly adhering layers of the above-mentioned with little effort Fabrics can be applied.

To solve this problem, a method for application a firmly adhering layer of powdery, non-metallic substances on one electrically conductive pad of any shape using electrophoresis proceeded according to the invention in such a way that the electrophoretically applied layer galvanically by depositing a metal or a metal alloy first the base and then the powder is fixed in the pores. This happens by that before the start of electroplating, the pores of the powder layer of air or gas with the aid of the electrophoresis suspension medium left in the pores or preferably by means of the into the pores using a wetting agent or vacuum and optionally pressure introduced electrolytes are kept free.

The electrophoresis suspending agent is left in the pores the powder layer, the powder layer becomes slow by diffusion replaced by the electrolyte. Following this liquid exchange Then the galvanic deposition of the metal contained in the electrolyte takes place. It starts first on the electrically conductive base of the powder layer it now. sheets, wires, sieves or be it plates or moldings made of metal, Carbon or graphite. The pores of the powder are slowly deposited with the Metal filled until the desired thickness of the electrodeposition is reached.

Depending on the intended purpose of the coating with the powder, one can interrupt the electrodeposition when the pores are completely or to the largest Part are filled. But you can also continue the deposition so that a layer consisting only of electrodeposited metal lies over the powder layer forms.

The last-mentioned mode of operation can then in particular have advantages if there is a grinding operation after the electrodeposition is made.

The ratio of the amount of powder applied to that deposited in the pores The amount of metal depends on the grain size and the grain structure of the electrophoretically deposited powder. It can be bariated through the choice of these influencing variables.

The firmly adhering layers produced are crack-free and tight.

However, there may also be a desire to use the applied powder layers to give a certain porosity. This can be B. be effected by one the powders that can be used for coating before they are applied to the metallic Base in a known manner with a thin film of varnish, paraffin or a similar suitable material. Are the powder particles thus pretreated by the deposition of metals in the pores of the powder layer enough firmly attached to the base, so you can apply it to the powder particles beforehand remove applied film of paint, paraffin or the like, e.g.

by immersing the coated master piece in a lubricated solvent. This process naturally takes a certain amount of time because the removal the applied layer can only be done by diffusion. An increase in temperature dissolving the organic layers can accelerate the dissolution of the layers.

The spaces thus formed between the powder particles or the binding metal, can then be filled with other substances, e.g. similar like that in powder trietallurgy to achieve particularly low friction values happens to soak with lubricants.

In case the electrophoretically applied layer before immersion has been completely or largely freed from the suspending agent in the electrolyte is what has the advantage that the suspending agent does not contaminate the electroplating bath, so it is necessary to add a wetting agent to the galvanic 3ad.

But it can also use vacuum to remove the air or from inside the pores the powder layer located gases are used so that the electrolyte in the cleared pore spaces of the ful layer up to the electrically conductive base can penetrate, patent claims:

Claims (2)

Claims: 1., A method for bringing an adhesive Layer of powdered non-metallic substances on an electrically conductive layer Base of any shape; using electrophoresis, characterized in that that the electrophoretically applied layer galvanically by depositing a Metal or a metal alloy first on the substrate and then in pores the powder layer is attached after the pores before the start of electroplating the powder layer has been kept free of air or gas with the help of the in suspensions left in the pores, by means of electrophoresis or preferably by means of into the pores with the help of a wetting agent or the application of vacuum and optionally Electrolytes introduced under pressure, 2. The method according to claim 1 for application predetermined porous layers, characterized in that the powdery substances before electrophoretic deposition with a top layer, preferably an organic, in a solvent-soluble layer, which can be provided after electroplating removed, preferably by solution with a solvent.