Four black technologies of titanium surface treatment
With the characteristics of light weight, high strength and corrosion resistance, titanium alloy has shown irreplaceable application value in the fields of aerospace, biomedicine and high-end equipment. But it also has fatal shortcomings: poor wear resistance, easy to stick to metal, and the surface is always a monotonous silver-gray color. In order to overcome these shortcomings of titanium and titanium alloys, surface treatments such as electroplating, micro-arc oxidation, electrophoretic coating and anodizing are often required.
1. Plating: Wear a "protective suit" for titanium
Principle:
Like "painting" metal, a layer of metal film is plated on the surface by electrolysis, which can prevent rust, wear and become beautiful.
Function:
1. Wear-resistant: The surface of Ti6Al4V titanium alloy is plated with nano-pure nickel, and the hardness and wear resistance are rising;
2. High-temperature anti-jamming skills: After the titanium blades are silver-plated, they will not be "welded" together by friction at a high temperature of 500 °C, and the "occlusion problem" of the aero engine will be solved by it.
Difficulty: Titanium is too easy to "make friends" with oxygen, and there is always an oxide film on the surface, which will be messed up during electroplating.
Solution:
1. Use nickel sulfate electrolyte and activator to "activate" the titanium surface with an electric pulse first, and then nickel plating.
2. Corrosion the titanium surface with hydrofluoric acid + dimethylformamide solution, and direct copper plating can also stick very firmly.
Two. Microarc oxidation: Allows the titanium surface to "grow" ceramic armor
Principle:
A layer of ceramic film is "burned" on the surface of titanium by high-voltage electric sparks, and the composition is mainly titanium oxide.
Function:
1. The ceramic membrane and the titanium matrix bite together like a tree root rooted in the soil, and it will not fall off when pressed to 200 MPa with a hydraulic press.
2. The film is hundreds of microns thick, as hard as ceramic, corrosion-resistant, wear-resistant, and heat-resistant.
Customized gameplay:
Adding potassium permanganate to the electrolyte can make a titanium film that is resistant to corrosion and antibacterial!
Three. Electrophoretic coating: "take a color bath" in titanium
Principle:
When titanium parts are placed in charged paint water, the paint particles will "line up" to the surface to form a paint film.
Merit:
1. Non-toxic, water-soluble, more environmentally friendly than traditional spray paint.
2. High degree of automation, 90% of the car body is primed with this trick.
3. Good biocompatibility, such as TA4 titanium alloy coated polyurethane, which can be used in the medical field.
Quick Facts:
Cathode electrophoresis is more powerful than the anode, with stronger corrosion protection and coverage.
Four. Anodizing: Engraving a "nano fingerprint" on titanium
Principle:
It is equivalent to 3D printing the reverse operation of metal, and titanium is energized as the anode, and an oxide film grows in the electrolyte, which is divided into two forms:
1. Dense type: tens to hundreds of nanometers thick, smooth and dense, good biocompatibility, suitable for anti-corrosion and medical.
2. Porous type: It can grow into a TiO₂ nanotube array in the fluorine-containing electrolyte, like countless nanopipettes.
Magic Apps:
1. The specific surface area of nanotubes is extra-large, which can be used as photocatalytic materials (decomposition of pollutants) and solar panels.
2. It is made into a hydrogen sensitive sensor, which is super sensitive to hydrogen, and has a fast and stable response.
3. Used in lithium batteries, anti-corrosion also improves charging and discharging efficiency.
