Study Of Corrosion-wear Behavior And Mechanis M Of Ni-W-P Alloy In Different Corrosion Environment

Corrosion-wear is the study on material removal, which takes place simultaneously by mechanical wear and by corrosion. The mechanical, chemical, electrochemical processes are involved in the ablation of the material. The phenomena of wear-corrosion is widespread in the field of mining, offshore, marine, biomedical, electricity industries, machinery and equipment, both directly and indirectly, impact the nation financially in terms of material loss and associated equipment downtime for repair, replacement of worn and corroded components. In order to reduce the loss of material through controlling the corrosion-wear rates, the proper use of metals and alloys, it is of important significance to study the corrosion-wear mechanism of metals.Due to its high hardness, high wear resistance, good corrosion resistance and other characteristics, Ni-W-P alloys have attracted more and more interests. Therefore the use of Ni-W-P alloys as a material system with a good potential in harsh environments, has great economic value and practical significance. So far, however, there are few studies on the corrosion-wear mechanism of Ni-W-P alloy.In this thesis, Ni-W-P alloys were fabricated by electrodeposition, The micro-morphology, micro-structure of alloys were studied by the scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), HVS-1000micro hardness tester. By the use of MMW-1tribo-tester, the effects of heat treatment on the properties of wear-corrosion in different solutions were studied. The more research work were as follows:(1) In deionized water, a series of experiments were carried out to study the sliding wear behaviour of prepared and heat-treated Ni-W-P alloys. Studies have shown that the wear mechanisms of prepared and heat-treated alloys were abrasive wear. Due to its lower hardness, Ni-W-P alloy at prepared state suffered more serious wear. Across the worn surface, deep furrows could be seen. Because of its highest hardness,400℃heat-treated alloy showed lowest wear rate and smoothest wear surface. Only a small number of furrows and shallows could be observed.(2) The static corrosion rates and the wear-corrosion rates of prepared and heat-treated Ni-W-P alloys in3.5wt.%NaCl solutions were studied. The results showed that, under the static corrosion conditions, the alloy at prepared state showed the best corrosion resistance. It also turned out that with the increase of the heat treatment temperature, corrosion resistance decreased at first and then increased. For Ni-W-P alloy heat-treated by400℃, it showed pitting in3.5wt.%NaCl solutions. The main wear was caused by abrasive, a few by fatigue wear and corrosive wear. For Ni-W-P alloy at prepared state, it showed uniform corrosion in3.5wt.%NaCl solution, the main wear was caused by corrosive and companied by fatigue and adhesive wear. During the corrosion-wear behaviour, Ni-W-P alloys at prepared state and at heat-treated state exhibited the synergistic effect in salt solution.(3) Studies showed that the alkali resistance of the alloy was prominent, it made no significant difference in wear-corrosion rates under various heat treatment conditions in1M NaOH solution. Only a small number of furrows and shallows could be observed.In this thesis, the selected contrast material was electress plating Ni-P alloy, the resistance to wear-corrosion in these solutions were far worse than the Ni-W-P alloys.