Effect Of CeO₂ On Microstructure And Friction And Wear Characteristics Of Plasma Sprayed Ti-Al/WC Cermet Composite Coatings

Ti-Al intermetallic compounds have excellent properties such as low density and high temperature resistance,and thus become a new structural material with great application value,and are widely used in aerospace,automobile manufacturing and other fields.However,due to its brittleness,especially TiAl is brittle at room temperature,it is inconvenient to shape and process,which limits its large-scale application.Therefore,a Ti-Al/WC composite coating can be prepared on the surface of a metal material by a thermal spraying method to exhibit the excellent properties of the Ti-Al intermetallic compound.In this paper,the orthogonal experimental method was used to optimize the plasma spraying process parameters,and the optimized process parameters were used to prepare Ti-Al/WC cermet composite coatings with different amounts of CeO₂ on the surface of 45 steel substrate.The microstructure,microstructure,phase composition and residual stress of the coating were determined by SEM,EDS,XRD,etc.,respectively.The dry friction and wear test at room temperature was performed using a friction and wear tester.The effects of different content of CeO₂ on the microstructure of the coating and the tribological properties of the coating were discussed.The main conclusions are as follows:?1?The optimal plasma spraying process obtained by orthogonal test is:spraying current700A,spraying distance 80mm,main gas flow rate 55L/min,ball milling time 4h,line speed20m/min.The microhardness and bonding strength of the Ti-Al coating prepared using the optimized process parameters were 357.43 HV and 43.72 Mp,respectively.The residual stress in the coating also decreased correspondingly,from 397.4 MPa to 294.7 MPa.?2?There are a lot of holes and defects on the surface of the plasma-sprayed Ti-Al/WC cermet composite coating,and the inside has a distinct lamellar structure,and the bonding with the substrate is a simple mechanical bond;the addition of CeO₂ can make the number of holes on the surface of the coating.Reduced,the lamellar structure is more fine,the bond between the plies is better,but the bonding mode does not change;the coating containing 2%CeO₂shows better microscopic morphology,indicating that the proper amount of CeO₂ can be improved Coating quality.Through the phase analysis,it is known that there is more W2C in the coating added with CeO₂,and TiN and Al₂O₃ are produced at the same time.These hard phases increase the hardness of the spray coating,and the average microhardness is about830.65 HV.The residual stress on the surface of the coating also decreased correspondingly,from 397.4 MPa to 294.7 MPa.?3?The coating added with CeO₂ showed better wear resistance than the unadded coating.Among them,the addition amount of 2%CeO₂ had the best improvement effect,the mass wear rate changed from 3.95 to 1.33,and the average friction coefficient decreased from 0.782.At0.366;at the same time,CeO₂ changed the coating wear mechanism,mainly from adhesive wear to abrasive wear,which strengthened the anti-friction ability of the coating and reduced the degree of wear,thus prolonging the service life of the coating.