Study on Microstructure of Laser Cladding Ti-Mo-Si Coating on Titanium Alloy Surface

In order to improve the hardness and wear resistance of titanium alloys, Zheng Liang and others at Shanghai University of Engineering Technology used a 5 kW YLS5000 fiber laser to laser cladding pure T powder and Ti-15% (Mo) on the surface of TC4 alloy.

+Si) and Ti-30% (Mo+Si) mixed powder (mass fraction, atomic ratio of Mo to Si is 1:2), through orthogonal experiment to select the appropriate power and scanning speed and other process parameters, three different coating. Use metallographic microscope (OM) and scanning electron microscope (SEM) to observe and study the apparent structure of the cladding layer, use X-ray diffractometer (XRD) to study the phase composition of the cladding layer, and measure three types with a microhardness tester The hardness of the cladding layer.

It was found that the surface of TC4 alloy was laser cladding T and Ti

15% (Mo+Si) and Ti-30% (Mo+Si) powder, the pure titanium coating has fine needle-like martensite a'phase, which is better fused with the substrate, and the coating dilution rate is small. The physical properties of the powder are similar to that of the matrix TC4, and it is easier to wet and fuse. Cladding mixed powder Ti-15% (Mo

+Si), petal-like dendrites appeared in the coating, and white strips of Tsi2 were co-precipitated between dendrites. Due to the dilution of the matrix, the presence of MoSi2 was not found, and Mo was mainly dissolved in aT and BTi. The cladding mixed powder T-30% (Mo+Si) has embedded massive Mo3Si3 and MoSi2 hard phases. The content of Mo element has a great influence on the phase composition of the coating. With the increase of Mo element, B-T becomes more, and the equiaxed crystal of the coating becomes less and refined. The hardness of the three coating cladding zones is T-30% (Mo+Si) powder, which reaches 9000~11500MPa, which is 3.4 times the hardness of the substrate on average. The methods of strengthening mainly include fine-grain strengthening and dispersion strengthening. To make the coating obtain the MoS2 phase with higher hardness, it is necessary to overcome the infinite solid solution of Mo and BTi, because the difference in the melting point of the elements causes Mo to melt in the T and Si molten pools, and it is easier to form Mos Si, o