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A Fe60 alloy coating was deposited on the surface of Q235 steel by semiconductor laser under the different preheating temperature at 25°C, 100°C, 150°C, 200°C, 250°C, 300°C respectively. The structure and hardness of the samples were analyzed by the means of OM、SEM、XRD、micro-hardness tester. The results show that: A Fe60 alloy coating with high Cr and C content was prepared on the steel substrate by using optimized process parameters, the interface bonding was formed between the coating and the substrate, the thickness of the coating without cracks and porosities is about 6-10mm. There are equiaxed and dendrite crystals in the coating and the phase of coating is composed of α-Fe, γ-Fe,{Fe,Ni} solid solution, Fe3C, Cr2B, Cr7C3. Preheating treatment has good eliminating coating cracks role in the laser deposited Fe-based coating with high Cr and C content, the sample preheated at 200°C has the finest crystalline structure, and the thickness is 8mm and the hardness is up to 806HV. Preheating treatment is an effective method to eliminate the cracks in the high thickness Fe60 alloy coating by laser direct deposition.

In situ synthesized TiBx/TiC reinforced composite coatings were prepared on Ti-6Al-4V substrate by laser in situ deposition using 10B4C-18TiNi-72Ti-6Al-4V (wt. %) powder blends as the feedstock materials. The microstructural analysis of the composites was performed using scanning electron microscope, and phase analysis was done with X-ray diffraction. The results showed that the composite coatings contained long needle TiB, irregular block TiB2 and disperse particles/dendrites TiC, the thick rod phase which was a inlay structure consisted of TiB2 and TiC. These composite reinforced phases were evenly distribution in the (TiNi+Ti2Ni+α–Ti) substrate.