Application of Magnesium Alloy Laser Surface Treatment Technology (II)

Wang AA et al. used Mg and Al alloys on the Mg matrix to detect the existence of Mg-Al alloys by selective electron diffraction spectroscopy (TEM). The corrosion resistance of the samples was better than that of Mg and Mg alloys. R Galun et al. used aluminum, copper, nickel and silicon as elements and used a 5 kW CO2 laser to alloy the magnesium alloy surface. The melting depth was 700-1200 μm and the surface hardness was 250 HV. The mass fraction of the alloying elements on the surface alloy layer is 15%-55%, and when the copper alloy is added, the corrosion resistance is greatly improved, and when the aluminum alloy is added, the corrosion resistance is significantly enhanced.

3 magnesium alloy laser surface cladding

Laser cladding technology uses high energy density laser beams to rapidly melt alloys with different compositions and properties to the surface of the substrate, forming a rapid solidification process on the surface of the substrate with alloy layers with completely different compositions and properties. The resulting surface alloy layer isolates the substrate from the corrosive medium and the material's corrosion performance is determined by the alloy layer. Magnesium alloy laser surface treatment does not require vacuum and other harsh environmental conditions, and has a small limitation on the size of the workpiece. In recent years, with the continuous improvement of laser cladding technology, its application in the corrosion resistance of magnesium alloy surface has been increasingly affected. The attention of researchers at home and abroad.

Wang Anan uses a 10 kW CO2 laser to laser-cut the magnesium alloy layer of pure magnesium in a reaction chamber similar to a vacuum-filled inert gas. A eutectic layer was formed on the interface, and the compositional phase of the modified alloy layer was α-Al and β-Mg2Al3. The corrosion potential was positively shifted by about 0.7 v, indicating that the laser-treated magnesium alloy had better corrosion resistance than pure magnesium.

Yue TM performed surface cladding of Al-Si eutectic alloy with Mg-SiC composite Nd:YAG laser under conventional environment, and laser cladding stainless steel with two-step process on Mg-ZK60/SiC composite. The Al-Si alloy layer covered by the former has no significant change in corrosion electromotive force, but the corrosion current density is reduced by 2 orders of magnitude compared to the matrix material. The metallurgical bonding layer of the latter sample is excellent, and the corrosion potential is 820-1090 mV, which is much higher than common ordinary materials and sprayed materials. The corrosion current 1 is reduced by 2 to 4 orders of magnitude, both of which have correspondingly improved the magnesium-based metal composite. Corrosion resistance of materials. In addition, YueTM also studied the laser cladding of amorphous alloy Zr65Al7.5NI10Cu17.5 on Mg-based metals using a powder blowing method with a cladding thickness of approximately 1.5mm. The substrate surface was covered with an amorphous layer and no crystalline structure appeared. . Cladding samples have excellent metallurgical bonding between the substrate and the surface, no porosity and cracks, and wear resistance and corrosion resistance are better than unclad samples.

4 Outlook

Magnesium alloy laser surface smelting method is simple and has improved hardness and corrosion resistance, but the degree of improvement is limited. The laser surface alloying can design alloy layers with different hardness. Although the interface is metallurgical, it is difficult to form a uniform alloying layer. Laser cladding can introduce high hardness, high corrosion resistance, and high melting point elements on the surface of magnesium alloys. It can form a strengthening layer with excellent surface properties and is metallurgically bonded to the substrate. It is an effective method to improve the surface properties of magnesium alloys.

With the development of gold, gold and metallurgy, robotics and automatic control technology, laser surface modification technology will move toward high-power automation and intelligence. Laser surface treatment technology has almost no negative effect on environmental protection. As a high-speed, high-efficiency surface modification technology, many achievements have been made in many aspects, and the role played by increasing the surface properties of magnesium alloys and prolonging their service lives has become more and more obvious. The economic benefits obtained are also becoming more and more significant. In the future, there will be great application prospects in anti-corrosion engineering.