Effect Of Composite Rare Earth Oxides On Microstructure And Properties Of Ti-Al/WC Coatings

With the continuous improvement of engineering technology,the application of parts under special working conditions is facing new challenges.Parts with the protective coating made by using thermal spray technology can often adapt to different working conditions and play a greater role.However,the coating generally has defects such as low bonding strength,uneven distribution of the tissue,and lots of holes.In the coating,rare earth elements are extremely active chemical elements,which can play a role in purifying the tissue,refining the grains,and improving the properties of the coating.In this paper,45 steel was selected as the base material,and both the Ti-Al/WC coating without rare earth oxides and the Ti-Al/WC coating with different composite rare earth oxides were prepared by plasma spraying.The effects of composite rare earth oxides on the microstructure and mechanical properties of the coating were studied by using a scanning electron microscope?SEM?with its own energy spectrometer?EDS?,a microhardness tester and an X-ray powder diffractometer?XRD?.The friction and wear test of the coating was carried out by the friction and wear testing machine.The effect mechanism of composite rare earth oxides on the tribological properties of the coating was analyzed.The main results are as follows:?1?Composite rare earth oxides can effectively improve the microstructure of the coating.The overall stratification of the coating is improved.The distribution of the tissue becomes uniform.The internal grains are refined.The diameter of the hole is reduced.The number and size of cracks are significantly reduced.The porosity of the coating is greatly reduced.They promote the dispersion distribution of hard phases W₂C and WC,and allow more C atoms to be converted into W₂C,which will be beneficial to the improvement of microhardness and wear resistance of the coating.The coating with three rare earth oxides CeO₂?Y₂O₃ and La₂O₃ has better microstructure than the coating with two rare earth oxides CeO₂ and Y₂O₃.?2?Composite rare earth oxides can improve the tribological properties of the coating.The friction coefficient of the coating during the wear process is reduced.The wear mechanism of the coating is changed.The wear morphology of the coating surface is significantly improved.The wear amount is reduced.Among them,the hard phase element's content of the coating with three rare earth oxides CeO₂?Y₂O₃ and La₂O₃ is more than that of the coating with two rare earth oxides CeO₂ and Y₂O₃.And its friction coefficient has the smallest fluctuation range,the average friction coefficient reaches the minimum,and the wear surface has the least defects and the best morphology.So the total wear is also the smallest.?3?Under the action of composite rare earth oxides,the microhardness of the coating's surface and cross section has been significantly improved.The residual stress on the surface of various coatings has decreased in different degrees,the bonding form of the interface between the coating and the substrate has changed,and the bonding performance has been enhanced.And three rare earth oxides CeO₂?Y₂O₃ and La₂O₃ have better effects on improving the mechanical properties of the coating than two rare earth oxides CeO₂ and Y₂O₃.