Study On The Microstructure And Properties Of The Laser Cladding Titanium With CNTs

Because the failure of materials always occurs in the surface of the substrate, the surface structure and characteristic have a direct influence on the service life of the materials. Titanium and titanium alloys have excellent corrosion resistance, high specific strength, high melting point, low density while the poor wear resistance limits its widely application. This experiment adopts the technology of laser cladding on the surface of pure titanium to improve its property while primary coating with carbon nanotubes which have a special structure. Attempting to get a good cladding layer, in the guarantee of titanium specific strength, high melting point and low density advantages at the same time, to obtain excellent friction and wear performance.This experiment studied the influence that laser cladding process parameters on the surface quality of cladding layer. Analyze the influence of the laser power, laser scanning speed on surface morphology, rough, microstructure and hardness, friction coefficient of the cladding layer. Comparison and analysis the relative between the changes of power, scanning speed and the morphology, microstructure and properties of cladding layer. On this basis, the section structure and phase composition under a certain technology are analyzed by XRD, friction and wear tester, and scanning electron microscopy (SEM). Discusses the organization of the hardening layer distribution and forming rules. Contrast the coefficient of friction, wear, the wear characteristics between the cladding layer and the pure titanium while the wear mechanism of cladding layer are discussed.The results show that:the laser parameter make a great influence with the quality of the cladding layer. As the loss of the laser scanning speed, the cladding layer crack begins to increase gradually and then decreases while present slice layer falls off phenomenon finally, the roughness of cladding layer decrease firstly and then increase while the minimum can reach2.5μm. As the loss of laser power, the surface quality of the cladding layer gradually smooth while the lack of fusion appears when the power is too low, the roughness begins decrease and then increase while best can reach2.1μm. Power density is proportional to the laser output power, and is inversely proportional to the laser scanning speed, with the increase of power density, the cladding layer internal organization in general from the dendritic structure to the petals structure change. After laser cladding compared with pure titanium surface hardness of cladding layer hardness can promote3-4times. The hardness in the cladding layer gradient reduced with the increased of the depth of cladding layer and the hardened zone can reach about650μm. The friction coefficient declined firstly and then increased as the power density increased, the best can reach to about0.2.The results show that:there are three different structure character in the laser cladding layer. As the depth of cladding layer increased, dendritic structure, petaliform structure and columnar structure can be observed. The wear resistance of cladding layer under1000W power with800mm/min speed increased compare with pure titanium.