Laser Surface Alloying With C And C+Nb In A TiAl Alloy And Its Oxidation Resistance At High Temperature And Wear Resistance Properties

γ-TiAl alloy is considered as one of the promising light-weight structural materials at elevated-temperature due to its excellent combination of low density, high specific strength and stiffness, and superior high elevated-temperature properties. How to improve high temperature oxidation resistance of TiAl alloy is one of keys to enhance the temperature for its application. At the same time, and the wear resistance of this alloy also must be improved when it is used as moving tribological components.In the paper, laser surface alloying with C and C+Nb powders with high purity was used to modify the surface properties of Ti-46Al-2Cr-1.5Nb-lV alloy, and a composite surface layer reinforced by "in-situ" titanium carbide was formed in the alloy. The microstructures of modified layer were observed, and the compositions were determined by using X-ray , SEM,Optical Microscope (OM) etc. The effects of laser process parameters on the microstructure of the modified surface were analyzed. The Oxidation behavior of the alloy with the modified surface was studied at 870癈 high temperature, and the wear properties of the modified layer at room temperature was investigated. The primary results are as follows:1. By laser surface alloying with C and C+Nb powders, a composite layer reinforced by "in-situ" TiC particles was produced at the surface of the alloy. TiC particles distribute at the surface in the gradient. The volume fraction of the particles decreased with the increase of the depth. No interface between modified layer and substrate was observed, indicating that they are in metallurgical bond.2. The microstructure of the modified layer was strongly dependent on the laser process parameters. At the conditions of the same powerand beam diameter, TiC changed in shape from the particle to the needle with the increase of the scanning rate.3. By laser surface alloying with C and C+Nb powders, the oxidation resistance at 870℃ of alloy improved obviously after, and the sample alloying with C+Nb exhibits the best oxidation resistance.4. At 870℃, TiC can decompose after oxidation for l00h.5. Micro-hardness of laser modified layer decreased continuously with the increase of the depth. Its highest hardness value and gradient were associated with laser process parameters, namely, slower scan rate and greater laser power result in a higher average hardness value and a smoother gradient.6. By laser surface alloying with C+Nb, the gliding wear resistance of the alloy at room temperature was improved greatly. The wear resistant mechanisms are mainly micro-cutting, slight adhesive transfer and fragmentation and spalling of the reinforcing phases resulting from partial cracking.