Research On Green Low Temperature Salt Bath Nitriding And Surface Friction And Wear Properties Of Titanium Alloy For Aviation

Titanium alloy is widely used in aerospace,defense industry and other fields.Due to its high specific strength and excellent corrosion resistance,it is the most promising light material to replace alloy steel as aeroengine structural parts in the 21st century.However,due to its poor wear resistance,it has limited its application as aerospace structural parts.Therefore,nitriding the surface of the titanium alloy can effectively improve its wear resistance.Nitriding methods for titanium alloys are vacuum low-pressure nitriding,high-temperature gas nitriding,ion nitriding,etc.,which are more common and have been studied at home and abroad.After nitriding by the above method,the wear resistance of the titanium alloy has been significantly improved,but due to the high temperature environment,the probability of phase transformation and deformation of the titanium alloy is increased.However,in the application of aero-engines,this kind of deformation will affect the accuracy of its structural parts,so low-temperature salt bath nitriding has become an ideal method of chemical heat treatment for the surface of titanium alloys.In this paper,rare earth-cyanate is used for surface low-temperature salt bath nitriding of titanium alloy TC4.Under the catalysis of rare earth,the active nitrogen atom[N]produced by the decomposition of cyanate radical CNO-penetrates into the surface of the titanium alloy,making the surface obtain a 15-30?m thick composite layer.After low-temperature salt bath nitriding,the surface hardness of the infiltrated layer can be increased to more than 700HV0.1,which is about 1.5 times that of the substrate(380-460HV0.1).The wear resistance of the surface of the permeated layer has been effectively improved:the average friction coefficient is 0.3-0.4,which is about 50%lower than the friction coefficient of the substrate surface(0.6-0.7);the wear quality of the surface of the permeated layer is reduced by about 0.5-1 times.The volume is reduced by about 5 times.However,cyanate CNO-can also be decomposed into some highly toxic cyanide CN-,which poses a greater safety hazard to environmental protection and the health of operators.Add a small amount of potassium sulfate K2SO4 to the nitriding salt bath,and its sulfate SO42-can effectively inhibit the cyanide content.The results show that the cyanide content of the nitriding salt reactant after adding potassium sulfate is only 0.237%,which is nearly doubled compared to when potassium sulfate is not added(the cyanide content at this time is 0.444%),which is Low temperature green nitriding on the surface of titanium alloy.Figure[36]Table[9]Ref.[80]...