Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons

Definitions

• the invention relates to a method for producing an anodic oxide layer on an object consisting at least in a surface layer of a eutectic or hypereutectic AlSi alloy.
• Eutectic and hypereutectic AlSi alloys are also used to manufacture wear-resistant objects. Due to the high Si content on the alloy side, they contribute to increasing wear resistance. Highly Si-containing aluminum alloys can hardly be anodized, however, so that simultaneous corrosion protection in the form of a compact anodic oxide layer is not possible.
• the inventors have set themselves the goal of providing a method with which objects made of high-Si-containing aluminum alloys can be anodized.
• the particle size of the Si or Si-containing crystals in the surface layer of the object is brought to a size of about 5 ⁇ m by melting or melting before the anodic oxidation.
• the size of the Si precipitates in high Si-containing aluminum alloys which is usually on the order of 10 ⁇ m or more, makes it impossible to form a compact anodic oxide layer.
• the reason for this is that the crystals, which conduct electricity well, conduct it directly from the anode to the cathode in the anodizing bath and thus cause a short-circuit current, thereby preventing the formation of a compact anodic oxide layer.
• the particle reduction carried out according to the invention before the anodic oxidation now enables aluminum alloys with a high silicon content to be provided with a compact anodic oxide layer. This improves the corrosion behavior on the one hand and on the other hand increases the wear resistance by incorporating the Si-containing particles in the oxide layer.
• Si is introduced into the surface layer simultaneously with the melting or melting.
• the Si content of the surface layer is preferably at least 13% by weight of silicon.
• the particle size of the Si- or Si-containing crystals is expediently a maximum of 5 ⁇ m, in particular a maximum of 3 ⁇ m.
• the surface layer is preferably melted or melted using high-energy radiation, in particular by laser radiation.
• the laser radiation is expediently brought about by a CO2 laser.
• the high-energy radiation can also be electron radiation.
• An object made of an AlSi7 cast alloy was melted on the surface by a CO2 laser, at the same time aluminum-silicon powder was introduced into the melting zone, which bonded to the substrate.
• the laser beam was focused on the surface with a power of 1500 watts at 1 mm diameter and passed over the object at a speed of 2 meters per minute. This process was repeated 3 to 4 times, a 0.7 mm thick layer of aluminum with 13% by weight of silicon being built up. Then about 0.1 mm was mechanically turned off the porous surface and then the object was degreased and anodized in a sulfuric acid electrolyte with 200 g H2SO4 / liter at 20 C and 1.5 A / dm2 for 40 minutes. After the compression process in boiling water, the object had an oxide layer thickness of 12 ⁇ m.
• Example 2 The procedure was as in Example 1, but a composition of the aluminum / silicon powder was chosen such that the layer contained 25% by weight of silicon. Mechanical preparation, anodic oxidation and compression were carried out as in Example 1. The oxide layer thickness was 19 ⁇ m.
• Example 1 The procedure was again as in Examples 1 and 2, but the surface of the article was subjected to a heat treatment with the CO2 laser after the coating process. The object was then mechanically turned off, degreased and anodized as in Example 1.

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• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (2)

Cited By (4)

Citations (4)

• 1990
  • 1990-11-28 CH CH3764/90A patent/CH682327A5/de not_active IP Right Cessation
• 1991
  • 1991-11-07 EP EP91810864A patent/EP0488944A1/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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