Search

• By high-speed laser cladding technology, the decomposition degree of WC is weakened. • The composite coating with high content of WC (60%) is prepared. • Three decomposition mechanisms of WC particles are deeply revealed. Ni/WC composite coatings with different compositions were prepared on the surface of 304 steel by high-speed laser cladding (HSLC). The microstructure and phase composition of Ni/WC composite coatings were analyzed, and the hardness and wear resistance of Ni/WC composite coatings were tested. The results show that the HSLC coatings have good surface formation without defects such as pores or cracks, and WC is uniformly distributed in the coating. WC particles hinder the dendrite growth, and the dendrite structure in the coating is significantly refined with the increase of WC content. The main phases of the coating is Ni 3 Fe, and the W and C elements diffuse into the coating, forming strengthening phases such as W 2 C and Cr 23 C 6. Although WC particles are decomposed, the strengthening effect of the second phase is not weakened, and the decomposed WC produces fine grain strengthening and solid solution strengthening effects, thus producing multiple strengthening mechanisms for the coating. With the increase of WC content, the hardness and wear resistance of the coating are gradually improved. However, when the WC content is in the range of 30–60%, the wear resistance of the coating do not present significant change. The main wear mechanisms are adhesive wear, abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

• When the scanning speed was 80.38 m/min, the volume fraction of amorphous phase was 74.48%. • When the scanning speed was 80.38 m/min, the crack of the coating section almost disappeared completely. • The residual tensile stress on the coating surface decreased with the increase of scanning speed. • Under the scanning speed of 80.38 m/min, the cooling rate of the coating could reach 1.08 × 105 °C/s. Fe-Co-B-Si-Nb amorphous coatings were deposited on 45 medium carbon steel under different scanning speeds by high-speed laser cladding technology. The results showed that the surface roughness of the coating became lower and the surface of the coating became smoother with the increase in scanning speed. In addition, the residual tensile stress and the thermal expansion coefficient decreased with the increase in the scanning speed. When the scanning speed was 80.38 m/min, the residual tensile stress was 106.13 ± 24.03 MPa. The residual stress was reduced by more than 50% compared with the scanning speed of 37.68 m/min. The XRD and TEM observation results of the coating at the scanning speed of 80.38 m/min showed a large volume fraction of amorphous phase and some crystalline dendrites. Under the scanning speed of 80.38 m/min, the cooling rate at the top of the coating could reach 1.08 × 105 °C/s, which greatly increased the amorphous formation ability. The hardness and wear resistance properties of the coating were also tested and analyzed. Better performance of the coatings was obtained when the scanning speed was higher. [ABSTRACT FROM AUTHOR]

• High quality FeCrMoMn coatings were fabricated by high-speed laser cladding. • Mechanism of laser acting on powders during high-speed laser cladding. • Metallurgical behavior of solute trapping during rapid solidification of laser molten pool. • Evolution mechanism of corrosion resistance of high-speed laser clad coatings. In this research, FeCrMoMn coatings with excellent corrosion resistance and metallurgical quality were deposited on the 45# steel substrate by conventional and high-speed laser cladding at the scanning speed of 0.4 m/min, 40 m/min and 70 m/min, respectively. Their microstructure, phase composition, hardness and corrosion resistance were characterized and compared. The results show that compared with the conventional cladding, high-speed laser cladding leads to a decrease in grain size, heat affected zone, and the dilution rate of the coatings due to solute trapping of coatings. Metallurgical bonding is formed between the substrate and the coatings, and the hardness and electrochemical corrosion resistance of the coatings are also significantly improved. [ABSTRACT FROM AUTHOR]