Various characteristics and technical description of hard oxidation treatment

The formation mechanism of the hard oxide film is the same as that of ordinary sulfuric acid anodization, but in order to obtain a thick and hard film layer, it is necessary to use an electrolyte of about 0 degrees Celsius, and a high voltage and high current method to make the film formation speed far greater Due to the dissolution rate, the film structure changes, which constitutes a new feature of the hard oxide film growth process. The hard oxide film is also a double-layer structure. The difference is that the barrier layer thickness is 10 times larger than that of the ordinary oxide film, and the hole wall is also the same, which is one of the basic reasons for the high hardness. However, the porosity is 7-8 times less than that of ordinary oxide films. Only 2% to 6%, the basal dura mater is disorderly and interferes with each other, and a special prismatic shape appears. The internal stress of the membrane is large, and even cracks are caused, and Alloy elements and electrolytic decomposition products remain in the membrane wall. Causes the color of the oxide film to be dark and the color of the alloy composition is different. Alloy composition and impurities have a greater impact on hard oxidation, it affects the uniformity and integrity of the oxide film, Aluminum copper, aluminum silicon. Aluminum manganese alloy is more difficult to oxidize hard.

Various characteristics and technical description of hard oxidation treatment:

1. Features: Hard oxidation is an electrochemical treatment method that forms an extremely hard, high temperature, wear resistance, high resistance, and corrosion resistance hard oxide film on pure aluminum or aluminum alloy materials. This extremely high surface hardness, combined with the light weight, easy machining, and low cost of aluminum alloy, is widely used in various industrial and military applications. This is the time when China’s industrial upgrading is indispensable for precision industries. One ring.

2. Hardness: refers to the hardness of the film. Thickness refers to the two parts of Build up and Penetration. T=1/2Build up+1/2Penetration. The minimum hardness standard is that BS5599 stipulates that HRC36 or higher (about HV350) can exceed HRC60 (HV700) near the substrate.

3. Wear resistance: With a load of Taber Abraser CS-17 1000g, the abrasion resistance of hardened aluminum alloy is much better than that of hard chrome plating and other hardened steels.

4. Accurate size: The thickness of the film layer is generally 50±5μm, and the single-sided size of the component is increased by about 25μm. For finer tolerances and special thickness requirements, it must be specially marked on the drawing.

5. Corrosion resistance: After sealing and salt spray test (ASTM117 specification) over 5000 hours, no corrosion will occur.

6. Suitability of alloy materials: Suitable for all aluminum alloys, including 1000 pure aluminum series (1050, 1100), 2000 aluminum copper series (2014), 3000 aluminum manganese series, and 5000 aluminum magnesium series. 6000 aluminum-magnesium-silicon series (6061, 6063), 7000 aluminum-zinc series (7050) and cast aluminum alloy 514.2, A514.2, 518.2, ADC.5 ADC.6, etc.

7. Breakdown Voltage: up to 1500VDC or more.

8. High electrical resistance: 4Ⅹ10.15 ohm cm2/cm at 20°C, which can be used as a good insulator.

9. Heat resistance: The film has a melting point of 2050°C, which can protect aluminum from damage in a short time.

10. Low friction coefficient: The friction control coefficient of the polished surface can be as low as 0.095, so all kinds of ordnance and civilian equipment slides use this technology.

11. The bonding strength of the oxide film: The form of the hard oxide film is that half of the film grows out of the inner half of the aluminum, and the bonding force with the aluminum base metal is very strong. It is difficult to separate them by mechanical methods, even if the film layer follows The substrate is bent until it breaks, and the film layer and the substrate metal still maintain a good bond.

12. Porosity of the oxide film structure: The oxide film has a porous honeycomb structure, which can make the film exhibit good adsorption capacity for various organics, resins, inorganics, dyes and paints, and can be used as the bottom layer of the coating. The oxide film can also be dyed into a variety of different colors (hard oxide film, only black) to improve the decorative effect of the metal.

Precautions for making hard oxide:

1. All edges and corners on the product should be inverted into a circular arc with a diameter of not less than 0.5mm, and no sharp corners and burrs are allowed to avoid local overheating, brittleness and fracture caused by current concentration.

2. It is not required that the thick film parts be protected with vinyl chloride glue, etc., and the threaded holes and positioning pin holes are blocked with plastic or rubber.

3. After the product is hard-oxidized, the size increases by about half of the film thickness (single side). Therefore, for products with strict size requirements, the size margin before anodization should be determined according to the film thickness.

4. The oxide film is firmly combined with the substrate, but the film layer is brittle and increases and increases with the thickness, so it is not suitable for parts that bear impact, bending or deformation. A hard film with a certain thickness will greatly reduce the fatigue strength of aluminum alloys, especially high-strength aluminum alloys. Therefore, the hard oxidation of parts that bear fatigue loads should be very cautious.