Technical Progress of Laser Cladding Composite Powders and Ceramic Coatings
With the continuous improvement of material performance requirements in aerospace and energy equipment, traditional single-material systems can no longer meet the needs. Composite powder and ceramic coating technology, through the collaborative design of "metal toughness + ceramic hardness", is breaking through the performance limits of laser cladding technology. This paper systematically expounds the latest progress in this field from material design, process optimization to engineering verification.
Strengthening Mechanism of Composite Powders
Coated powders use a core-shell structure to solve the oxidation problem of carbides. In typical Ni-coated WC powders, a 5-15μm nickel shell forms a (W,Ni) solid solution transition layer under laser action, reducing the carbon loss rate from 28% in mechanical mixing to below 5%. The more advanced in-situ synthesis technology uses the Ti+C→TiC reaction. When the power density >3×10⁴ W/cm², 50-100nm TiC particles can be obtained. A bearing ring application of this technology reduced the wear rate to 1.8×10⁻⁶ mm³/N·m.
Performance Comparison of Carbide-reinforced Systems
Comparison tests show that the interfacial bonding strength of coated powders reaches 580 MPa, an increase of 65% compared with mechanical mixing. Particle size distribution design is particularly critical: 50-150μm coarse particles bear the main load, and 5-20μm fine particles fill the gaps. A steam turbine blade using the Ni60+35%WC (coated type) scheme extended its service life from 8,000 hours to 15,000 hours, verifying the engineering value of this technology.
Preparation Challenges of Ceramic Coatings
Zirconia gradient coatings reduce thermal stress by 60% through transitional design from metal→70% metal+30% ceramic→pure ceramic. Process parameter optimization shows that a power of 2-4kW with a scanning speed of 5-15mm/s and a lap rate of 30-50% can make the crack density <0.5 pieces/mm. An aero-engine combustor applied with this technology has a thermal cycle life of 3,000 times (the original technology only had 800 times).
Breakthroughs in Biomedical Applications
Hydroxyapatite (HAP) coatings increase crystallinity (XRD half-peak width 0.38°→0.25°) through 3%F⁻ substitution, and adding 3%MgO promotes osteoblast adhesion. Animal experiments show that the bone integration time of the modified FHA coating is shortened to 8 weeks (original 12 weeks), and the interfacial bonding strength reaches 35 MPa. This technology has been applied to clinical trials of dental implants with an initial success rate of 98.5%.
Core Components of laser Cladding System
Conclusion
Composite coating technology faces three major research directions: ①developing a multi-scale collaborative strengthening theoretical model; ②establishing service performance evaluation standards (such as thermal shock test methods); ③reducing the preparation cost of coated powders. It is recommended to form an "industry-university-research-medical" consortium to focus on breaking through bottleneck technologies such as Ta coatings for cardiovascular stents and ZrO₂-HAP gradient materials for artificial joints.