Application and prospects of laser surface treatment technology
Laser processing technology is developed rapidly in recent decades a high and new technology.
In laser surface modification technology research and application in ferroalloy.
Discusses the application of laser in the magnesium alloy surface treatment technology of the trend of development and broad prospects.
Magnesium alloys have the advantages of small density, specific strength, specific stiffness, good thermal conductivity, good electromagnetic shielding characteristics and damping shock absorption ability.
Magnesium alloy has replaced many zinc, aluminum, cast iron and steel and other materials, widely used in aerospace, automobile, computer, communication and other industries, especially in automobile industry, the demand for magnesium alloy parts is increased continuously, make the application of magnesium alloy showed a strong momentum of development.
However, magnesium alloys with poor wear resistance, corrosion resistance, restrict the potential of magnesium alloy.
As a result, the magnesium alloy surface treatment technology attaches great importance to by the researchers.
Laser surface treatment technology is a new technology developed in recent years, relative to the surface modification of magnesium alloy materials processing technology, the laser method, through selecting wavelength of local rapid heating and make it produce a specific chemical reaction, so on the material surface modification more can play a huge role.
Laser surface treatment methods are mainly laser surface phase transition and impact hardening, laser surface fused, laser surface alloying, laser surface cladding, etc.
Among them, used in the laser surface modification technology of magnesium alloys is fused, laser alloying and laser cladding.
1, the magnesium alloy surface fused laser is fused with high power density of laser interaction within a very short time and metal, the metal surface local instantaneous heated to very high temperature and melt, then with the help of the cold metal matrix absorption of heat and heat transfer process of molten metal surface rapid solidification, thus change the microstructure and mechanical properties of parts surface.
Because this process is done under rapid heating and rapid cooling, so get organization of hardening layer is thin, the hardness is higher than that of conventional quenching hardness.
The technology improved the metal materials and parts surface hardness, wear resistance, corrosion resistance and strength and high temperature performance, etc.
Under the condition of vacuum, high and beautiful on AZ91HP magnesium alloys such as laser fused processing.
The results showed that laser fused magnesium alloy layer mainly by alpha 3 / Mg and beta
With the increase of the laser scanning speed, fused layer hardness, wear resistance also will increase.
But under different scanning speed, laser fused magnesium alloy corrosion resistance than matrix layer decreases, and with the loss of the scanning speed, the fused layer increased corrosion resistance decreased.
AKousomichalis, who love equal KrF laser irradiation under vacuum conditions in polished AZ3lB4H sample surface.
Find the sample surface microscopic morphology of corrugated, and compared with no processing the surface of the sample after laser treatment is tensile stress.
30 microns laser processing layer is lower than that of the matrix hardness, laser treated samples have great improved corrosion resistance.
Using Nd: YAG laser, DDube on two kinds of magnesium alloy AZ91D and AM06B fused laser treatment, the microstructure in dendritic, grain size refinement, although after laser heat treatment of AM60B magnesium alloy corrosion resistance than AZ91D, but didn't get significant improvement.
Even under some parameters can significantly reduce corrosion resistance.
Yaojun for laser fused in the surface of AZ91D mg alloy, such as the microstructure of the formation of fused relatively uniform, accordingly improve the wear resistance of laser fused layer.
On 2 kw cw CO2 laser, G.
Abas on A3Z1, AZ61 and WE43 magnesium alloy surface by laser fused, fused specimen under 20 ℃ was submerged in the pH value of 10.
Sodium chloride (5
The mass fraction of 5%)
10 d in the solution, the result shows that after laser fused magnesium alloy corrosion resistance improved, refine the microstructure of alloy, increases the alloy elements in.
Phase of the solid solution concentration, make the beta phase distribution more uniform, formed the corrosion resistant layer 1.
2, laser surface alloying, laser surface alloying of magnesium alloy by melting substrate surface coating film layer and part of the substrate in advance or at the same time of surface melting note some powder, coating or surface rapid solidification in the aftermath of the liquid mixture in the molten pool, thus formed in the surface layer 1 has expected performance of the alloy thin layer, in order to improve the performance of matrix.
In recent years, aluminium and aluminium alloy is more active, laser surface alloying research for magnesium and magnesium alloy of the research of laser surface alloying is not a lot.
WangAA etc in Mg and Al magnesium substrate by laser alloying, through TEM district electron diffraction spots discovered the existence of the magnesium alloy, corrosion resistant properties of the samples is better than that of cast magnesium and magnesium alloys.
RGalun etc. Use the element such as aluminum, copper, nickel and silicon, using 5 kwco2 laser of the magnesium alloy surface alloying.
The melting depth is 700 -
1200 microns, the surface hardness is 250 hv.
The mass fraction of surface alloy layer of alloy elements is 15%
55%, and copper alloys, corrosion resistant performance improved substantially, and the aluminum alloy corrosion resistance was significantly enhanced.
3, magnesium alloy laser cladding on the surface of laser cladding technology is the use of high energy density laser beam will have different component, the performance of the alloy and substrate surface melting fast, formed in the substrate surface and substrate has a totally different composition and properties of the alloy layer of rapid solidification process.
The generated surface alloy layer of the substrate from corrosion medium, the corrosion performance of the material is decided by the alloy layer.
Laser surface treatment of magnesium alloys due to harsh environmental conditions, such as do not need to vacuum the workpiece size limit is small, in recent years, with the constant improvement of laser cladding technology and its application in the corrosion resistance of magnesium alloy surface is more and more attention by researchers.