Research On Preparation And Properties Of Cr-Mo Alloyed Layer On γ-Tial Modified By Double Glow Plasma Surface Alloying

At a certain pressure, temperature and operating conditions, Titanium alloy will oxidize, burnand spread quickly, called “Titanium fire”. The flammability limits its application under certainservice conditions. To solve the above problems, a Cr-Mo alloyed layer was explored for the surfacemodification of-TiAl alloy by using double glow plasma surface alloying. In order to get a goodmodified layer, this paper first studied the processing technology and the microstructure, compositionand phase structure were analyzed. Subsequently, the hardness and adhesion load values were tested.And the research focuses on the friction and wear resistance at room temperature and hightemperature, high temperature oxidation resistance and burn resistance properties.The results indicated that the optimum process parameters were justified as follows: sourcevoltage:950V; cathode voltage:500V; pressure:48Pa; pole spacing:18mm; holding time:3hours.Under these conditions, the formation of surface modification layer was metallurgical bonded with thesubstrate, and the thickness was approximate to6μm. XRD shows the surface was mainly composedof Al8Cr5, Al5Mo, TiCr and TiAl phases. The micro-hardness after infiltration was significantlyincreased to1053.4HV0.1.Friction and wear test results showed: the coefficient of friction, wear scar width, wear scar depthof the Cr-Mo modified sample were less than TiAl base sample, particularly the coefficient of frictionreduced volatility significantly, the wear loss was much lower than the base sample. The wearresistance was improved by the surface alloying at a greater degree.Isothermal oxidation test results showed: the oxidation products were mainly the mixture of TiO2and Al2O3for TiAl substrate, TiO2particles were thick, then the porous oxide film was easily oxidized;the high temperature oxidation resistance obtained was improved to some extent for the alloyedsample, the oxidation product were Cr2O3, Al2O3, TiO2and a small amount of MoO3, the dense oxidefilm remained intact which could effectively prevent the oxygen into the substrate.Laser ignition test showed that the minimum burning power and suface temperature distributionwere greater than the TiAl substrate, and the treated sample did not appear severe cracking, cracksphenomena, the existence of the alloy layer was not conducive to the spread of combustion, the burnresistance performance was improved to a certain extent.