Finite Element Simulation And Experiment Of Cold Forming Processing For Ti-based Composite Pipe Fittings

Titanium pipe-fittings with ceramic coatings were prepared using a new composite process in this work to improve their surface hardness, corrosion resistance and wear properties..Firstly, the Ti/Al composite tube blanks were produced by explosive welding. The microstructure, element distribution and phase composition around the interface of the composite tubes were characterized respectively with the aid of scanning electron microscope (SEM), energy dispersion X-ray spectrum (EDS) and X-ray diffraction (XRD).The results showed that the metallurgical bonding occurred without any microcracks at the interface between Al and Ti matrix, and the microstructure around the interface was Ti-Al solid solution. The bonding strength of composite tubes was investigated individually by means of compression shear test, flattening test and upset test.Then, the Marc software was used to simulate the hydroforming process of T-shapes and push bending process of elbows. It was found that more than 5MPa interface bonding strength and less than 0.1 friction coefficient were needed with internal pressure 100MPa and feed distance 25mm in the hydroforming process. For the push bending process, the critical interface bonding strength was 50MPa, friction coefficient was less than 0.15. Ti/Al composite T-shapes and elbows with high size accuracy and good bonding strength were manufactured successfully according to the simulation results.The Al₂O₃ coatings were prepared by micro-arc oxidation. The adhesion strength, corrosion resistance and tribological behavior of Al2O3 coatings were investigated individually through scratch adhesion test, electrochemistry work station and ball-on-disc tribological test. The results reveal that the Al2O3 coatings have the bonding force of over 55N. The corrosion current of the Al2O3 coatings decreases dramatically by 5 magnitudes owing to their compact structure. Furthermore, the prepared coatings possess good wear resistance with friction coefficient 8 times lower than that of the titanium substrate.The above analysis indicates that the numerical simulation can guide the practical forming of Ti-based composite pipe-fittings effectively. Ti-based composite pipe-fittings with Al2O3 coatings prepared by a new composite process can improve their wear resistance and corrosion properties, significantly.