The Experimental Research Of Wear & Corrosion Resistant Technology For Partial Surface Of The Piston Rod

The piston rod is one of the important components of compressor, which works in the conditions of high temperature, high speed, dry friction and being easily eroded. Currently, the main partial surface strengthen treatment technology for the compressor piston rod at home includes the following methods, such as the plasma spray WC coating, the electro-plated hard chromium, the plasma nitriding. However, the defects of the above approaches are high-cost, heavy environmental pollution and complex operation processing craft. Therefore, it is urgent to look for a new technology which has good performance both in wear & corrosion resistant and processing craft to replace the above technologys. In this paper, the tribological properties of the plasma spray Al₂O₃/TiO₂ coating, nano-composite electro-brush plated n-SiC coating (NEPC) and the plasma arc surface quenching layer, which are used for the piston rod, were particularly analyzed in variable sliding velocity and loads.The experimental results clearly indicate that: (1) The coefficient of Al₂O₃/TiO₂ coatings decrease along with the increase in sliding velocity, but it decrease along with the increase in the load, however, the further increase of the load leads to the decrease in the coefficient. Al2O3-13%TiO2 and Al2O3-40%TiO2 coatings show good wear resistant performance with low friction coefficient when sliding velocity and load are low, while Al2O3-20%TiO2 coating is vice versa. And the wear mechanisms of Al₂O₃/TiO₂ coating are ceramic pellet flaking, layer flaking and intenerated daubbing. (2) The wear resistance of the NEPC is significantly enhanced resulting from nano-particles. The wear mechanism of NEPC is abrasive wear, and that of the pure nickel coating is abrasive wear and adhesion wear. (3) Both the surface micro-hardness and quenching depth obtained by the plasma arc surface quenching are strongly satisfacted for the requirement of technique demand for the compressor piston rod. Furthermore, the coefficient of the quenching layer is reduced with the increase in sliding velocity, and the wear rate is correspondly going up because of the increase in sliding velocity and load. And the wear mechanisms of the plasma arc surface quenching are abrasive wear, plastic deformation and adhesion wear.According to wear and corrosion resistant, the plasma spray Al₂O₃/TiO₂ coating is more suitable for high sliding velocity and load, However, the plasma arc surface quenching layer is inclined of being applied for low load and high sliding velocity. In the view of economy, NEPC can be used for repairing the wear surface of the piston rod, whereas the plasma arc surface quenching is available to strengthen the new piston rod. As to environmentally sound technology, the plasma arc surface quenching, which are not only having facility operation processing craft, but also favorable for environment, could be the optimal choice in this project.