Laser Cladding Technology and Analysis of Core Cladding Powder Materials

1. Overview of Laser Cladding Technology

Laser cladding technology is a process in which selected coating alloy powders are placed on the surface of a substrate through specific filling methods, and then irradiated by a high-energy laser beam. This irradiation causes the powder and the substrate surface to rapidly melt, spread, and solidify, ultimately forming a cladding layer tightly bonded to the substrate. This cladding layer can significantly improve or even reengineer the performance of the substrate, enabling it to achieve functional goals such as wear resistance, heat resistance, corrosion resistance, and oxidation resistance.

As a complex physical-chemical metallurgical process, the quality of laser cladding is mainly affected by two key factors: first, the setting of laser parameters, and second, the selection of alloy powders. According to their compositions, alloy powders can be divided into self-fluxing alloy powders, composite powders, ceramic powders, and other metal-based powders. The performance differences of various powders directly determine the cladding effect.

2. Classification of Core Cladding Powder Materials

(1) Self-Fluxing Alloy Powders

Self-fluxing alloy powders are the most widely studied and applied category at present. Their core characteristics include containing boron (B) and silicon (Si) (endowing them with self-deoxidation and slag-forming capabilities) as well as high chromium (Cr) (preventing oxidation of liquid metal and improving wettability). They have good adaptability to substrates such as carbon steel, stainless steel, and alloy steel, and can reduce inclusions and oxygen content in the cladding layer. However, it should be noted that their compatibility with sulfur-containing steel is poor—brittle phases are prone to form at the interface, leading to peeling of the cladding layer. They are mainly classified into three types:

Type	Core Advantages	Main Disadvantages	Applicable Scenarios
Iron-based (Fe)	Wide material sources, low cost, excellent wear resistance	High melting point, poor oxidation resistance, prone to cracking/porosity	Parts requiring local wear resistance and deformability (cast iron, low-carbon steel substrates)
Nickel-based (Ni)	Excellent wettability, strong corrosion resistance, high-temperature self-lubrication, moderate price	Single powder cannot withstand extreme wear	Scenarios with sliding/impact/abrasive wear (can be reinforced by adding ceramic particles)
Cobalt-based (Co)	Outstanding heat resistance, corrosion resistance, wear resistance, impact resistance, and high-temperature oxidation resistance	High cost	High-temperature, wear-resistant, and corrosion-resistant scenarios in petrochemical, electric power, and metallurgical industries

Key Selection Principle: Nickel-based/cobalt-based powders have comprehensive performance but high prices, while iron-based powders have high cost-effectiveness but limited performance. The choice should balance cost and functionality based on application requirements.

(2) Composite Powders

Composite powders are formed by mixing or compounding high-melting-point hard ceramic materials (carbides, nitrides, borides, oxides, etc.) with metals. Their core value lies in the preparation of "ceramic particle-reinforced metal matrix composite coatings" via laser cladding. These coatings not only retain the toughness and processability of metals but also integrate the wear resistance, corrosion resistance, and high-temperature resistance of ceramics. They can reduce the oxidation and decomposition of ceramic phases and obtain high-hardness wear-resistant coatings, making them a current research focus.

Among them, carbide and oxide composite powders are the most widely used, and coated powders (e.g., nickel-coated carbides, cobalt-coated carbides) offer the best performance: the coating metal protects the core ceramic particles, avoiding burning loss, decarburization, and volatilization caused by laser irradiation, thereby improving coating stability.

(3) Ceramic Powders

Ceramic powders are mainly composed of silicides and oxides (primarily alumina and zirconia). Zirconia, due to its low thermal conductivity and excellent thermal shock resistance, is often used to prepare thermal barrier coatings. Overall, ceramic powders exhibit excellent high-temperature wear resistance and corrosion resistance, making them an important choice for high-temperature coating applications.

Research Focus: Bioceramic materials (e.g., hydroxyapatite, fluorapatite) exhibit good biocompatibility and can be used for surface modification of titanium-based alloys and stainless steel, meeting the needs of the medical field. Although research in this area started late, it has developed rapidly.

3. Technical Advantages and Application Scenarios

Compared with traditional surface technologies such as surfacing, thermal spraying, and electroplating, laser cladding has the following advantages:

Low dilution rate, dense structure, and strong bonding force between the coating and substrate;
Wide adaptability to materials, with a large adjustable range of powder particle size and content;
High processing quality and strong controllability (supporting 3D automated processing).

(2) Main Applications

Material Surface Modification: For key components such as hydraulic rams, rolling rolls, gears, and gas turbine blades, wear-resistant and corrosion-resistant alloys are clad to extend service life without deformation;

Product Surface Repair: Repairs worn components such as rotors, molds, and bearing inner holes. After repair, the strength can reach over 90% of the original strength, with costs much lower than replacement and significantly shortened maintenance cycles, solving the emergency repair problem of large-scale equipment;

Low-Cost Manufacturing: High-performance alloys are clad on the surface of low-cost metal substrates, which not only retains the properties of the substrate but also saves precious metals and reduces manufacturing costs .