Research On Modification Of Laser Cladding Metal-ceramic Composite Coating On The Surface Of Titanium Alloy

Titanium alloys have been widely used in aerospace, energy, automotive manufacturing, biomedical industry etc. because of their excellent comprehensive properties. However, titanium alloy shows poor hardness and wear resistance, limiting its application in industries. Wear resistant coatings, heat resistant coatings and abrasion resistant coatings can be made on the surface of metal materials by laser cladding. Metal-ceramic composite coating receives much concern due to its advantages of metal material's good toughness and easy wetting and ceramic material' wear resistant and wear resistance. Therefore, the metal-ceramic composite coatings including the addition of ceramic reinforcing particles and in-situ synthesized ceramic composite materials were made on titanium alloys by laser cladding in the paper, which has practical application value and theoretical significance.The metal-ceramic composite coatings were prepared at the surface of titanium alloys by means of laser cladding process using the cladding material which contains Ti, Ni, Si3N4, ZrO2, C, BN at the optimization of process parameters. XRD, SEM, EDS, EPMA were used to characterized the microstructure of the coatings. DHV-1000 type digital Vickers hardness testers was used to test the micro-hardness of the coating. CFT-I type multifunction material surface tester was used to measure the dry sliding friction and wear.The results of laser cladding Ti/Ni+ Si3N4/ZrO2 composite coating show that:White m-ZrO2 particles, fine dendrites containing TiN, Ti5Si3 distribute in the network matrix containing NiTi, Ti2Ni uniformly in the coating. The addition of ZrO2 in the coating can refine grain and ZrO2 was dispersive in the coating with the phase transition from the tetragonal to monoclinic phase, which has the function of toughening. Besides, a certain amount of ZrO2 can improve the properties of the coating. The highest micro-hardness containing ZrO2 of coating is reached 1123.6HV that is about 4 times of TC4 substrate. The wear resistance of the coating containing ZrO2 is about 3times that of the coating without ZrO2,9 times that of the substrate.The experiment of laser cladding Ti5Si3-Ti(C, N)/TiNi-Ti2Ni on titaniums indicates that: the properties of the coating changes with the content of C. When the C content is 3 wt.%, the Ti(C, N) with the morphology of fine dendrite and particles and the Ti5Si3 with the morphology of dendritic and lamellar evenly distributed on the matrix of the coating containing TiNi and Ti2Ni. Besides the hardness of the coating reaches 1000HV, that is about 3 times of the substrate and the wear resistance of the coating is about 5.5 times of the substrate. When the C content is 5 wt.%, the rod Ti3SiC2 appeared and the hardness of the surface coating is less than the coating containing 3 wt.% C, the bottom of the coating is higher than the coating containing 3 wt.% C. The hardness of the coating containing 5 wt.% C reaches 1000HV, which is about 3 times of the substrate and the wear resistance is about 2 times of the substrate.The experiment of laser cladding TiB-Ti(C, N)/TiNi-Ti2Ni composite coating shows that:TiB with the morphology strip and Ti(C, N) with the morphology of dendrites distribute evenly on the matrix of the coating containing TiNi and Ti2N.The hardness of the coating reaches 1080HV,which is about 3times of the substrate. Besides, the Ti(C, N) and TiNi in the coating has good toughness. The wear resistance of the coating is about 6 times of the substrate, which is higher than the Ti5Si3-Ti(C, N)/TiNi-Ti2Ni composite coating.