| QBe1.9 alloy, as a typical Beryllium Copper alloy, has been widely used in the fields of aerospace, petrochemical, electronic and electrical due to its good corrosion and fatigue resistances, high elasticity and excellent electrical thermal conductivity. However, the low hardness and poor wear resistance limit the application of QBe1.9 alloy under the condition of the friction and wear. In this paper, double glow plasma surface metallurgy technology and plasma nitriding were applied in QBe1.9 alloy to improve its wear resistance. Ti/N modified layers were formed in QBe1.9 alloy substrate by the composite technology of plasma titanizing followed by plasma nitriding and plasma titanizing + nitriding permeation, respectively. The surface morphology, microstructure, composition distribution, phase structure, resistivity, adhesion between alloyed layer and substrate, surface hardness after Ti-alloyed, Ti-N and Ti+N alloyed layers were analyzed. And the sectional hardness and elastic modulus of different alloyed QBe1.9 were analyzed by using nano-indentation test. Compared with the untreated QBe1.9 substrate, the wear properties of modified layers as well as the mechanisms of friction and wear resistance were investigated. The results are shown as follows:(1) Ti-alloyed layer was formed on QBe1.9 substrate by double glow plasma surface metallurgy technology firstly, and then treated by plasma nitriding to prepare the Ti-N duplex layer. The results reveal that the Ti-N layer, with a thickness of 30?m, is composed of TiN, Ti2 N, Cu-Ti intermetallic compound and BeCu substrate phase. The thickness of Ti+N alloyed layer is about 15?m and the phase composition mainly contains TiN and BeCu substrate phase. Both the Ti-N and Ti+N alloyed layers have continuous composition distribution and compact structure and show a good adhesion strength with substrate.(2) The resistivity of Ti, Ti-N and Ti+N alloyed layers is 0.096??·m, 0.094??·m and 0.093??·m respectively, which are higher than that of QBe1.9 substrate slightly because Ti and TiN have a higher resistivity than Cu and Be.(3) The surface hardness of Ti, Ti-N and Ti+N alloyed layers is 467 HV, 979 HV and 786 HV respectively, slightly higher than that of QBe1.9 substrate. Both The hardness and elastic modulus of Ti-N and Ti+N alloyed layers are decreased gradiently with the increase of alloyed depth.(4) Under 5N load dry sliding friction condition, the friction coefficient of QBe1.9 substrate is 0.5, while the friction coefficient of Ti, Ti-N and Ti+N alloyed layers is 0.5, 0.13 and 0.55 respectively. And their specific wear rates respectively are 32%, 19% and 30% of the untreated QBe1.9. Ti-N duplex-treated QBe1.9 shows an excellent performance of antifriction and wear resisting.(5) Under 10 N dry sliding friction conditions, the friction coefficient of Ti, Ti-N and Ti+N alloyed layers is 0.5, 0.13 and 0.55 respectively, lower than QBe1.9 substrate(0.58). The specific wear rates of the modified layers drops to 30%, 21% and 25% respectively compared with the substrate. The Ti-N duplex layer still exhibits a better tribological performance with load increasing.(6) The improved wear resistance properties of Ti-aollyed QBe1.9 is attributed to solid solution strengthening of Ti. Besides Ti effect, nitride dispersion strengthened is the main reason of higher wear resistance after Ti-N and Ti+N treatmnets. In addition, the gradient hardness of diffusion layers play a certain role in supporting pressed load, which is helpful to the tribological properties. |
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