Research On Laser Cladding Technology Of Titanium Alloy And Coating Characteristics

Having high specific strength and good corrosion resistance, Titanium alloys arewidely used in the aviation and aerospace, petrochemical industries, automobilemanufacturing and other industries. However, these surface defects of weak hardnessand weak resistance to wear restrict largely its applications in friction mechanism,which can be improved well by Laser Cladding Technology. To obtain excellentcladding layer on the titanium alloys the following three parts is studied in the paper.First of all, considering the latent heat and thermal property change withtemperature, the mathematic model and three dimensions finite element model areestablished, the process in which Ni45is cladded on TC4surface is simulated by thesoftware of ANSYS, the three dimensions temperature field and stress field of meltpool are obtained, the influences of process parameters on the thermal stress fieldmolten pool, pool shape and dilution rate are investigated, the optimum processparameters(P=2400W, V=5mm/s, D=3mm) are obtained, all of which can be used toguide further experiment.Moreover, combined with the ANSYS results, the L16(44) orthogonal test isdevised and the Laser Cladding experiment is carried out by CO2Laser. Theinfluence law of energy density on cladding layer’s morphology is summarized.Experiment shows that an excellent cladding layer can be received when energydensity is controlled within178~254J/m2. The measurement result confirms thatMicro hardness of cladding layer is4~5times higher than the base, which means thatthe surface hardness of Titanium alloys is improved effectively by means of LaserCladding. The orthogonal analysis is applied to investigate the influence of processparameter and WC on micro hardness of cladding layer, by which best processparameters is obtained. SEM results show the metallurgical bonding is achieved in thebinding region of cladding layer, which contains mainly the dendrite, equated crystal,cellular dendrite, black hard particles and intergranular eutectic structure. And theimpact of WC content on cladding layer is investigated. EDS is applied to measure theelement composition of those crystal structures.At last, crack control experiments in which metal nets of different diameter andmesh are placed between base and coating is applied to investigate the impact of different kinds of net on crack rate. The conclusion is that it’s an effective method ofcontrolling crack to place metal net between base and coating in Laser Cladding andit’s very important to choose rational diameter, mesh and material of metal net. Forexample, stainless steel net is more effective than iron net in controlling crack forLaser Cladding.