Surface Modification Of Titanium And Titanium Alloy By Pulsed Plasma Detonation Technology

Pulsed plasma detonation technology(PPD),combining the gas explosion and the plasma,can form a wear resistant and corrosion resistant layer on the material surface through alloying reaction and self-quenching effect during rapid heating and cooling.Although TA2 and TC4 have excellent comprehensive mechanical properties,their wear resistance is poor.PPD treatment used on the surface of TA2 and TC4 can improve their wear resistance and corrosion resistance and expand their application fields.In this paper,PPD treatment was carried out on the surface of TA2 to investigate the effects of process parameters,including the capacitance(C),the pulse number(N),the cooling gas(CG),on the microstructure,morphologies and properties of TA2.Under the same process parameters,the microstructure,morphologies,properties and strengthening mechanism of the modified layer on TA2 were compared with that on TC4.The effects of different process parameters on the wear resistance and corrosion resistance of TA2 and TC4 modified layers were studied and their wear mechanism were also analyzed.The results showed that the surface modified layer of TA2 was composed of Ti N,Ti N0.3,Tix Oy,Ti and a few W phases.With increasing the capacitances and pulse numbers,the surface roughness,thickness and average hardness of the TA2 modified layers increased,and the columnar dendrites in the modified layers became more developed.Air was the better cooling gas than argon or nitrogen.When the capacitance was 800 ?F,the pulse number was 2 and the cooling gas was air,the TA2 modified layers had the best comprehensive performance,its surface roughness was 3.44 ?m,and the highest hardness,located at 20 ?m from the surface of the layer,was about 709.9 HK0.01,which was about 3.8 times higher than that of the substrate.Under the same process parameters,the phases of the modified layer on TC4 were basically the same with that on TA2,but Ti N0.3 phase only existed in the modified layer of TA2.Compared with TC4 modified layer,although the grain size of TA2 modified layer was larger,its hardness was higher.The main strengthening mechanism of the modified layers on TA2 was the second phase strengthening,combined with the fine grain strengthening,dislocation strengthening and solution strengthening.However,the main strengthening mechanism of the modified layers on TC4 included surface nanocrystallization,second phase strengthening and solid solution strengthening.Compared with the substrate,both the friction coefficient and wear volume of the PPD treated TA2 reduced.However,the friction coefficient of the treated TC4 increased slightly,while the wear volume reduced significantly.The wear mechanism of two substrates was abrasive wear and adhesive wear.After PPD treatment,the wear mechanism of the two modified layers was three-body abrasive wear with slight adhesive wear characteristics.When the wear time was long enough,the fatigue wear characteristics could be found on the worn surface of the treated TA2.The corrosion resistance of two modified layers treated in nitrogen was better than that treated in air and argon.With increasing the pulse numbers,the corrosion resistance of modified layers on TA2 gradually decreased,while the modified layers on TC4 increased first,and then decreased.