| TC11is a titanium alloy developed by China independently, which has many advantageousproperties such as high strength in elevated temperature, good corrosion resistance, excellent thermalstability and creep resistance. This alloy could work in long-term at500℃. But due to that its lowerthermal conductivity, higher friction coefficient, severe adhesive wear of components made of TC11has occurred commonly. It is also sensitive to fretting wear, greatly affect the safety of titanium. Thisbecomes an obstacle to the applications in aircraft engine. In this paper, a molybdenized layer wereprepared on TC11by double glow plasma surface alloying to improve its tribological properties. Sothat the application bottleneck may be broken.The main research topics include:（1） Studying on the plasma molybdenizing process on the TC11,investigate the influence of major parameters on the thickness of the diffusion layer as well as mainproperties so that an optimum process is concluded.（2） Characterizing of the alloyed layer, includingmorphology, composition distribution and phase composition, by OM, SEM, EDS and XRD.（3）Investigating of the basic mechanical properties by scratch testing, measuring of micro-hardness, andnano-indentation.（4） Evaluating of the tribological behaviors of the diffusion layer as well assubstrate by a serious ball-on-disc rubbing tests at different loads, temperatures, speeds and frictionmaterials. The wear rate of each specimen was calculated. Some explanations of the wear mechanismsunder diffirent conditions were given out,Analyzing the effects of various parameters on the thickness and major mechanical properties ofmolybdenizing layer, the optimum process parameter is concluded as below: source voltage950V;cathode voltage450V; pole spacing15mm; working temperature950℃; working pressure40Pa; time3h. The prepared molybdenized layer under the optimum process is uniform and dens. Molybdenizedlayer consist of a deposition layer and a diffusion layer with a totall thickness of30μm. The content ofMo in out surface reaches65%and decrease gradiently from outside to inside. The adhesion strengthbeteew deposited layer and substrate is about70N. The surface hardness on layer is1034HV0.1. Thediffusion layer mainly consists of pure molybdenium, compound Al8(Ti3-xMox)（0＜x＜3） andAl3Ti.The wear resistance results show that the plasma modified layer are greatly improved than thesubstrate under a variety of factors. At different speed of load330g, the modified layer wear between5-10m/min is mild wear,10-20m/min is serious wear, while the matrix between5-15m/min is minorwear,15-20m/min for severe wear. Under different load conditions, the layer wear in each speedbelongs to stable wear, and the matrix at10m/min and15m/min exist stable wear with linear changes,5m/min and20m/min stages both have mild wear and severe wear. Different temperature wear goeson in different mechanism, but the wear rate of the matrix is much larger than the diffusion layer, theturning point of matrix is at200°C, but that of layer is300°C; Kinds of friction pairs determinedifferent friction mechanisms and wear rate, the wear rate of nitrided layer and substrate is1.6timesand1.26times respectively than against GCr15when they rubbed against Si3N4ball. |
