High Temperature Tribological Properties And Wear Rate Forecasting Of Molybdenum Disilicide

Friction and wear properties research of ceramic materials at high temperature is a hotspot of tribology. However, ceramics is difficult to be made into complex precision component and has low mechanical reliability, which hinders its application in the engineering areas. Intermetallic compound MoSi2 has better performance such as high hardness, high elasticity modulus, high thermal conductivity and electricity conductivity, superior oxidation resistance and electrical discharge machining. MoSi2 will be expected to use as a new type of wear resistant material under high temperature circumstance.In this paper, MoSi2 and 0.8wt.%La2O3-MoSi2 composites were prepared by self-propagating high-temperature synthesis(SHS) and vacuum sintered. Alumina, Silicon carbide and silicon nitride were used as friction disc, while MoSi2 and MoSi2-based composites as pin. The effects of temperatures (700～1100℃), loads(10～50N), sliding velocity(0.084-0.252m/s) on its frictional and wear properties were investigated by using XP-5 type high temperature friction and wear Tester. The wear mechanisms were also studied. A network forecasting model for wear rate is built with artificial neural network technology. The friction and wear properties of MoSi2 coatings were also studied. The results are shown as follows:1. With the ambient temperature, load and sliding speed increasing, the friction factor of MoSi2/SiC and MoSi2/Si3N4 gradually reduced, and the wear rate also reduced. However, the friction factors of MoSi2/Al2O3 increase first and then decline. With the ambient temperature increasing, the wear rate of MoSi2 increases first and then decline. With the load and sliding speed increasing, the wear rate of MoSi2 gradually reduces. In the three pairs, the friction factor of MoSi2/SiC is the smallest and the ware rate is also the smallest. From the perspective of couples, SiC ceramic is more suitable couples for MoSi2 material at high temperatures.2. The oxidation wear of MoSi2 materials always exists during the wear process. With the load increasing, the main wear mechanisms of MoSi2 are adhesion wear, grinding and fatigue fracture. With temperature increasing, the main wear mechanisms of MoSi2 are adhesion wear, grinding and fatigue fracture.With Sliding velocity increasing, the wear mechanisms of MoSi2 change from scratches abrasive to adhesive and grinding.3. The wear resistance of MoSi2 is improved by adding La2O3 into MoSi2 substrate due to the strengthening and toughening. The oxidation wear of rare-MoSi2 materials always exists during the wear process. With the load increasing, the main wear mechanisms of rare-MoSi2 materials are adhesion wear, grinding and fatigue fracture. With temperature increasing, the main wear mechanisms of rare-MoSi2 materials change from adhesion abrasion to grinding and adhesion wear. With sliding velocity increasing, the wear mechanisms of rare-MoSi2 materials are adhesion wear, grinding and grind scratch.4. The friction and wear properties of the K403 alloy and MoSi2 coating at 1100℃were compared. The results show that the wear resistance of K403 alloy is improved after coated the MoSi2 coating and the wear resistance effect is more obvious after coated 30Vol.%ZrO2-MoSi2. The wear mechanisms of Nickel-based alloys are oxidation wear and fatigue fracture. The oxidation of K403 alloy was prevented after coated MoSi2 coating. The wear mechanics of MoSi2 coating are oxidation, adhesion wear, and fatigue fracture.5. Based on the artificial neural network and BP neural network analysis, the adaptive learning rate and additional secondary momentum BP neural networks prediction model were studied. The network training process was also given. Network prediction and the actual testing results show that the improved BP neural network has higher prediction accuracy. Network prediction can meet the predicting need of molybdenum disilicide under the complex conditions.