Research progress of laser cladding iron-based alloy coatings

Laser cladding is an advanced surface engineering technology that uses high-energy laser beams as heat sources to quickly melt and solidify alloy powder or wire of specific composition on the surface of the base material to form a metallurgically bonded coating.This technology can not only significantly improve the surface properties of materials,such as wear resistance,corrosion resistance and hardness,but also enable the repair and remanufacturing of damaged parts.Among them,laser cladding iron-based alloy coating has shown broad application prospects in the engineering field due to its high strength,high hardness,good metallurgical bonding properties and low cost.This article will review the research progress of laser cladding iron-based alloy coatings in recent years,discuss the latest achievements in its design ideas,structural control and mechanical properties,and look forward to the future development direction.

1.Overview of laser cladding technology

The basic principle of laser cladding technology is to focus the laser beam on the surface of the base material,so that it can quickly heat up to above the melting point locally,and melt the alloy powder or wire that is preset or fed synchronously to form a molten pool.As the laser beam moves,the molten pool quickly cools and solidifies,thereby forming a coating with specific organization and properties on the surface of the base.Compared with traditional surface treatment technology,laser cladding has the advantages of small heat input,low dilution rate,uniform and dense coating organization,and fine grains.

The key parameters of the laser cladding process include laser power,scanning speed,powder feeding rate,spot size,etc.These parameters directly affect the organizational structure,performance and process stability of the coating.In recent years,with the continuous advancement of laser technology,especially the application of fiber lasers and high-power diode lasers,laser cladding technology has developed rapidly,and its application areas are also constantly expanding.

1.Overview of laser cladding technology

The basic principle of laser cladding technology is to focus the laser beam on the surface of the base material,so that it can quickly heat up to above the melting point locally,and melt the alloy powder or wire that is preset or fed synchronously to form a molten pool.As the laser beam moves,the molten pool quickly cools and solidifies,thereby forming a coating with specific organization and properties on the surface of the base.Compared with traditional surface treatment technology,laser cladding has the advantages of small heat input,low dilution rate,uniform and dense coating organization,and fine grains.

The key parameters of the laser cladding process include laser power,scanning speed,powder feeding rate,spot size,etc.These parameters directly affect the organizational structure,performance and process stability of the coating.In recent years,with the continuous advancement of laser technology,especially the application of fiber lasers and high-power diode lasers,laser cladding technology has developed rapidly,and its application areas are also constantly expanding.

2.Ultra-fine eutectic reinforced iron-based coating

The ultra-fine eutectic structure is formed by finely regulating the alloy composition and solidification conditions to form fine and evenly distributed eutectic phases in the coating.This organizational structure can significantly improve the hardness and wear resistance of the coating.Research shows that by adding appropriate amounts of alloying elements and using optimized laser cladding processes,ultrafine eutectic structures can be obtained in iron-based alloy coatings,thereby significantly improving coating performance.

3.Particle-reinforced martensitic coating

Martensite is a microstructure with high hardness and good wear resistance.By adding hard particles(such as carbides,nitrides,etc.)to iron-based alloys,the hardness and wear resistance of the coating can be further improved.These hard particles play a role of dispersion strengthening during the laser cladding process,effectively hindering the expansion of cracks and improving the toughness of the coating.

4.High-hardness amorphous iron-based coating

Amorphous alloy is a new type of material with a special atomic arrangement,which has high hardness,high strength and good corrosion resistance.In recent years,researchers have tried to apply amorphous alloys to laser cladding coatings.By optimizing the alloy composition and laser cladding process,they have successfully prepared high-hardness amorphous iron-based coatings.This coating not only has excellent wear resistance and corrosion resistance,but also has good toughness and fatigue resistance.

3.Tissue structure regulation and mechanical performance improvement

The microstructure of laser cladding iron-based alloy coating has an important influence on its mechanical properties.By finely controlling the alloy composition and laser cladding process parameters,the coating structure can be optimized,thereby significantly improving its mechanical properties.

1.Alloy composition design

The alloy composition is one of the key factors that determine the structure of the coating.By adding appropriate amounts of alloying elements,such as carbon,silicon,manganese,chromium,nickel,etc.,the phase composition and microstructure of the coating can be significantly changed.For example,adding an appropriate amount of carbon can promote the formation of carbides,thereby improving the hardness and wear resistance of the coating;while adding an appropriate amount of silicon can improve the corrosion resistance and oxidation resistance of the coating.

2.Laser cladding process optimization

The influence of laser cladding process parameters on the coating structure is equally important.By adjusting parameters such as laser power,scanning speed,and powder feeding rate,fine control of the coating molten pool temperature,cooling rate,and solidification conditions can be achieved.Optimization of these parameters can not only promote the formation and uniform distribution of favorable phases,but also reduce the occurrence of defects such as cracks and pores.

3.Multiple types of precipitation strengthening

Precipitation strengthening is one of the effective means to improve the mechanical properties of coatings.By forming fine and evenly distributed precipitates in the coating,the strength and toughness of the coating can be significantly improved.These precipitated phases can hinder the movement of dislocations and the propagation of cracks,thereby improving the strength and toughness of the coating.For example,the formation of fine and evenly distributed carbide or nitride precipitates in iron-based alloy coatings can significantly improve the hardness and wear resistance of the coating.

4.Introduction of plastic/toughness phase

Introducing plastic/ductile phases into iron-based alloy coatings is another effective method to improve coating toughness.These plastic/tough phases can form a"toughness skeleton"in the coating,effectively hindering the expansion of cracks.For example,adding an appropriate amount of nickel element or forming an austenite phase in an iron-based alloy coating can significantly improve the toughness and fatigue resistance of the coating.

4.Future development direction and prospects

Although laser cladding of iron-based alloy coatings has made significant progress in research and application,there are still some challenges and problems that need to be solved.In the future,research on laser cladding of iron-based alloy coatings will continue to deepen from the following aspects:

1.Development of high-strength and tough cladding special materials

Through a combination of high-throughput material calculations and experiments,we develop cladding-specific materials with higher strength and toughness.These materials should have excellent metallurgical bonding properties,good processability and low cost.

2.Research on the mechanism of fine tissue regulation

In-depth study of the diffusion,phase transformation and precipitation behavior of alloy elements during the laser cladding process to reveal the formation mechanism and evolution rules of the coating structure.This will provide a theoretical basis for further optimizing the coating structure and improving mechanical properties.

3.Research on new iron-based laser cladding multi-component alloys

Explore and develop new iron-based laser cladding multi-component alloys with excellent comprehensive properties.These alloys should have high strength,high toughness,good corrosion resistance and wear resistance to meet the needs of different application fields.

4.Research on high-speed laser cladding technology

High-speed laser cladding technology is an effective means to improve cladding efficiency and coating quality.In the future,key issues such as powder transportation,laser-powder interaction,and molten pool solidification behavior in the high-speed laser cladding process will be studied in depth to achieve a more efficient and stable laser cladding process.

Conclusion

Laser cladding of iron-based alloy coatings has shown broad application prospects in the engineering field due to its high strength,high hardness,good metallurgical bonding properties and low cost.In recent years,researchers have made significant progress in coating design,structural control,and mechanical property improvement.However,there are still some challenges and issues that need to be resolved.In the future,with the continuous development of materials science,laser technology and computer simulation technology,research on laser cladding of iron-based alloy coatings will continue to deepen,providing strong support for achieving a more efficient,greener and smarter manufacturing process.