Stady: Introduction to Magnesium Alloy Laser Cladding Coating. Image Credit: Juergen Faelchle / Shutterstock.com
Magnesium alloy and laser coating
Magnesium alloys are good structural materials due to their low density, which results in highly specific mechanical properties, ease of fabrication, and low cost. The primary limitations of magnesium alloys are their low surface properties and low wear and corrosion resistance. One strategy to overcome these limitations is to use laser cladding techniques to create protective surface coatings.
Different ways of feeding laser cladding: (a) paste feed ; (B(powder injection)c) wire feed. (DrReady powder. Riquelme et al., Metals
The primary advantages of laser cladding over conventional methods include reduced thermal deformation of the substrate, improved surface properties with reduced attenuation, and improved surface quality. To obtain coatings with good mechanical properties, appropriate process parameters selection is required (laser power, powder feed, scanning speed, substrate and powder properties)
Laser manufacturing methods are divided into three types: laser cladding, laser alloying, and laser glazing. Laser cladding is a coating manufacturing technique that uses lasers as a power material to generate low porosity and improved coatings on metals. The laser alloying technology simultaneously simulates the feed material and the substrate, resulting in homogeneous metal alloys. Laser vitrification dissolves only a small portion of the substrate and rapidly cools, resulting in amorphous crystals.
This study examines the current processes in magnesium laser cladding and investigates the effect of the most important manufacturing factors on the interaction of different substrate systems used in mechanical properties and corrosion resistance.
The coating process was carried out using a laser cladding system, which includes a laser (diode laser, Nd: Yag or CO . laser).2 laser), an excimer laser, and a feed material, sprayed with a carrier gas and axial to the laser beam. The feed material is a spherical powder that is sprayed with a carrier gas through a coating nozzle. The cladding nozzle laser is related to the motor control system, which usually consists of a CAD (computer-aided drafting) system and a moving robot or xy motion table.
Inputs, outputs, and processing parameters for laser cladding. Riquelme et al., Metals
Influence of process parameters
According to various studies, the input parameters affect the laser cladding of magnesium alloy and to obtain a high-quality coating, the optimum combination of scanning speed and laser power must be determined. The geometry of the coating, dilution, melting, and heat sensitivity are all affected by the focal position of the substrate surface. The wavelength of the laser beam has a great effect on the absorption of reflective metals. The energy absorbed by the substrate expands the dilution area, which affects the microstructure and properties of the coating.
The output laser cladding parameters are determined by input factors such as the dilution rate, coating geometry, the presence of cracks and pores, which are mainly controlled by the laser, the movement device and the properties of the feed materials.
Most metallic, binary, and ternary alloy coatings include Mg-Al because Al increases the hardness of Mg; However, the addition of Al alloy to Mg reduces the corrosion performance. The presence of Al allows some phases to be generated to conform to the Al-Mg equilibrium phase diagram, and the presence of other metals leads to the formation of the Al-metal or Mg-metal phases.
Study of high-entropy (HEA) coatings (AlCoCuFeNi coatings) on pure magnesium reveals that dilution between the substrate and the coating helps detect some CuMg2 dendrites.
Studies on the manufacture of ceramic coatings on magnesium alloys indicate that ceramics have a low affinity for interaction with a magnesium substrate, forming other compounds, improving the substrate microstructure, and improving the substrate’s wear resistance and wear resistance.
The researchers studied the effect of process parameters on the magnesium laser cladding. According to the researchers, the most researched matrices are aluminum-based alloys, and frequently used ceramic reinforcements often have a particle shape because these composite coatings combine improved tribological properties with higher wear resistance.
Understanding how different coating fabrication parameters affect the final surface properties of magnesium alloys is critical to their use in a wide variety of manufacturing situations. In the future scale, multiple processes such as laser cladding welding or 3D printing can be combined with direct laser deposition as an extension of the laser cladding process.
Source: Riquelme, A.; Introduction to laser cladding coating for magnesium alloy. metal 2021, 11, 1993. https://www.mdpi.com/2075-4701/11/12/1993