A review on coatings deposited by extreme high-speed laser cladding: processes, materials, and properties

•The influence of process parameters on the thickness of EHLA coating was reviewed, and the mechanism of process parameters on the formation of defects was discussed. Under the premise of obtaining a high surface quality coating, reducing the power can significantly decrease the temperature gradient between the coating and the substrate, which prevents thermal expansion and the generation of cracks in the coating. Minimizing the coating thickness, which requires increasing the scanning speed and matching the appropriate powder delivery rate, means a shorter path for pore escape.•The factors that affect the properties (corrosion resistance, wear resistance, high temperature resistance) of the coatings in various material systems were listed. The primary reason for EHLA to improve coating performance was microstructure refinement and uniform distribution of components.•The generation mechanism and elimination method of defects in the molten pool under a high energy laser were summarized in detail. In addition to controlling process parameters, the preparation of EHLA coating under an external field was also an effective method to eliminate defects. In recent years, the industry has required critical parts with excellent high-temperature resistance, wear resistance, corrosion resistance, and other properties. Preparing high-performance coatings on part surfaces is considered an efficient and economical method. As a new surface treatment technology, extreme high-speed laser cladding (EHLA) has attracted increasing attention owing to its high cladding efficiency and rapid cooling rate. EHLA can maintain good metallurgical bonding between coating and substrate at low heat input. It can significantly promote the refinement of microstructure and uniform composition distribution. In addition, optimization of EHLA parameters allows for control of coating thickness and inhibition of defect formation. This paper introduces the research progress of extreme high-speed laser cladding technology in detail from cladding process optimization, process simulations, material systems, and defect types. The setting of process parameters, the factors affecting the EHLA coating performance, and the formation mechanism of defects are also summarized.