Insitu-fabrication of TiCN Ceramic Coating on Titanium Alloy by Laser Cladding Technology

摘要

The insitu-fabrication of TiCN ceramic coating by laser cladding-laser nitriding technique (LC-LN) was investigated. Pulsed YAG laser with the power of 500W was used as radiation source. Highly pure N_2 was selected as the nitriding element; Titanium powder whose size is 20 urn and the pure carbon powder were utilized as the coating materials. The influence of technology parameters such as pulse width, pulse frequency and scanning speed etc. on the insitu-formation of TiCN ceramic coating was studied. XRD results show that the main phases of the coating are TiC_(0.3)N_(0.7) (or TiC_(0.2)N_(0.8)), TiN and TiN_(0.3). It was revealed that the appropriate process parameters for insitu-fabrication are the pulse frequency 15 Hz, pulse width 3.0ms, the scanning speed in the range of 9cm/min to 12cm/min, the pressure of N_2 0.4MPa. The result of OM showed a metallurgical bonding without crack and bubble between the coating and the substrate was obtained. The microstructure of cladded coating is characterized by fine dentrites. The average microhardness in the coating is more than 1300HV which is about 4 times of that in the substrate.