Study On Nitride Ion Diffusion And Deposition Behavior On The Surface Of Titanium And Titanium Alloy

Titanium and its alloys are widely used in aerospace,medical and health,energy and other fields due to their excellent comprehensive properties.However,titanium and its alloys exhibit poor tribological properties,including high and unstable friction coefficients,severe adhesive wear.Additively manufactured titanium alloys have a lower elastic modulus,which can provide space for bone growth to achieve better fixation capabilities.This is considered a good alternative to compact implants,but its Corrosion resistance cannot meet the needs of the human environment.Strengthening treatment on the surface of titanium and titanium alloys can improve the physical and chemical properties of the surface.The purpose of strengthening the surface can be achieved by ion nitriding and surface coating treatment of titanium and its alloys to generate titanium nitride.In this paper,the low-temperature(furnace temperature<600?)nitriding of titanium alloy is realized by equipping the hollow cathode device in the traditional ion nitriding furnace.By setting the temperature gradient,the influence of temperature on the internal structure and properties of the cast Ti6Al4V(TC4)alloy was studied.Through ion nitriding of the cast and additive manufacturing Ti6Al4V(TC4)alloy,the structure and morphology of the titanium alloy after nitriding in two manufacturing methods were studied.And the difference in performance,the surface of TA2 pure titanium was subjected to ion nitriding and multi-arc ion plating to prepare a modified layer of the same thickness,and the difference in structure,morphology and performance of the modified layer prepared by the two processes was studied.X-ray diffractometer(XRD),X-ray photoelectron spectrometer(XPS),optical microscope(OM),three-dimensional white light interference profiler,scanning electron microscope(SEM),transmission electron microscope(TEM),Vickers hardness tester,Friction and wear experiments and electrochemical workstation analysis and testing of its structure,surface morphology,mechanical properties,corrosion resistance and wear resistance.The main research contents are as follows:(1)For the cast TC4 alloy,with the increase of the nitriding temperature,the intensity of the diffraction peak of TiN phase gradually increases,the intensity of the diffraction peak of Ti2N phase gradually weakens,and the intensity of?-Ti first decreases and then gradually increases.The growth rate of the composite layer increases exponentially with the increase in temperature.The compound layer on the surface is composed of solid solutions of TiN,Ti2N and N in?-Ti.The bottom of the compound layer is the diffusion zone of nitrogen,and the bottom of the diffusion layer is the matrix after heat treatment.The influence of temperature on the surface of the nitriding sample and the nitrogen diffusion zone is very obvious.(2)The?-Ti phase is not detected in the untreated additive manufacturing samples.As the nitriding time increases,the strength of the?-Ti phase decreases in both the casting and additive manufacturing TC4 samples,and the?-TiN(200)and?-The strength of Ti₂N(221)is significantly increased.The?-TiN on the surface has a unique texture and fine grains,and it forms multiple twins interlaced with each other.Under the same processing conditions,the roughness of the additive manufacturing samples before and after treatment is lower than that of the casting samples,and the hardness is higher than that of the casting samples.The hardness of the additive manufacturing samples is the highest at 1298HV_0.1,which is about that of the untreated sample(312HV_0.1).4 times.The maximum polarization resistance of the sample processed by additive manufacturing at 500?and 5h is 4.159*10⁶?�cm^-2,which is increased by two orders of magnitude.The self-corrosion current density is 1.412*10^-8A�cm^-2,and the corrosion resistance is excellent.(3)TiN,Ti2N,TiN0.30 diffraction peaks were detected on the surface of the nitriding sample,and the multi-arc ion plating coating sample only has the diffraction peak of the?-TiN phase,and the(111)direction is the preferred orientation and has a single growth direction.The coating samples treated with 6h coating have the highest nano-hardness and elastic modulus,which are 20.676 GPa and 323.757 GPa,respectively.Under oil lubrication conditions,the friction coefficient of the untreated sample fluctuates sharply,oscillating between 0.3 and 0.55.After nitriding and coating treatment,the friction coefficient is stably maintained below 0.15,and the wear resistance has been greatly improved.