Effect Of Impact Corrosive-wear Behavior On The Synergism Of High Manganese Steel And High Chromium Cast Iron

The wet grinding process is complicated owning to the synergistic effect of wear and corrosion, and resulting in tremendous material removal. However the material removal in wet grinding conditions was generally accepted to be dominated by wear, and extensively studied from the viewpoint of wear by simplifying the working condition to pure wear. And there are few reports on wear with corrosion in wet grinding condition. Therefore this investigation on corrosive wear and their mutual action behavior and mechanism is significant in theory and reality for selecting and developing corrosive wear resistant materials.In this dissertation, the high manganese steel and the high chromium cast iron were selected as testing materials. Their corrosive wear behaviors were systemically investigated by conducting weight-loss test, electrochemical techniques, scanning electron microscope (SEM), energy dispersion spectrum (EDS), and X-ray diffraction (XRD).The effect of impact energy and polarization potential on the corrosion-wear synergy of high manganese steel and high chromium cast iron under corrosive impact abrasion conditions was studied. The contributions of individual factors to the total material weight loss were quantified.A set of impact corrosive wear tester was designed to simulate the wet grinding process, which had the advantages of weight loss and electrochemical testing equipment. The tester could measure the weight loss and electrochemical parameters simultaneously, and it possessed good operation performance and data reappearance.Oxygen aeration and stirring accelerated the transportation of oxygen to the surface, and the corrosion rates were 1.05 and 2.04 times more than that of static corrosion respectively. Plastic deformation of austenite high manganese steel induced by impact wear process facilitated anodic dissolution and accelerated the transport of oxygen, which strongly accelerated the anodic and cathodic process of the electrochemical corrosion. With the increasing of impact energy, the electrochemical corrosion rates increased, which were 15.76,22.00,23.39 and 26.54 times more than that of static corrosion respectively.Oxygen aeration accelerated the transportation of oxygen and formation of passive film, and the corrosion rate was decreased to 17% than that of static corrosion. Impact wear severely accelerated the inter-phase corrosion by breaking or thinning the passive film, which strongly accelerated the anodic process of the electrochemical corrosion. With the increasing of impact energy, the electrochemical corrosion rates increased, which were 45.97,57.55 and 63.86 times more than that of static corrosion respectively. The corrosion rate of high chromium cast iron was higher than high manganese steel, which indicated the effect of passive film to the electrochemical corrosion was stronger than that of the plastic deformation.The leading failure mechanism of high manganese steel were gouging and plowed crinkle under the circumstances of low impact energy, while the leading failure mechanism was fatigue spalling under the circumstances of high impact energy. The leading failure mechanism of high chromium cast iron were microcutting and ploughing under the circumstances of low impact energy, while the leading failure mechanism was extending crack induced fracture under the circumstances of high impact energy.Anodic dissolution of high manganese steel was enhanced by anodic polarization and the corrosive wear rate increased. The formation of passive film was accelerated by anodic polarization as to high chromium cast iron. However the passive film was vulnerable to broken and increased the corrosive wear rate. Cathodic protection could effectively reduce the corrosive wear synergy of high manganese steel and high chromium cast iron, decreasing the corrosive wear rate.Although the corrosiveness of ore slurry was relative weak to the two materials, but corrosion was strongly accelerated to a certain extent by the wear. The synergistic effect increased with the increasing of impact energy as to the high manganese steel, which accounted for 12.08%,19.50%,23.11% and 26.70% respectively. Under the circumstances of 1J, the synergistic effect was mainly caused by plastic deformation accelerated corrosion, while wear-accelerated corrosion was the major contribution of synergy. Under the circumstances of 2J,3J,4J, wear was largely accelerated by the deteriorating of fatigue property, while corrosion-accelerated wear was the major contribution of synergy.The synergistic effect increased with the increasing of impact energy as to the high chromium cast iron, which accounted for 26.65%,27.17% and 36.50% respectively. Under the circumstances of 1J and 2J, the synergistic effect was mainly caused by the broken of passive film and inter-phase corrosion, while wear-accelerated corrosion was the major contribution of synergy. Under the circumstances of 3J, the synergistic effect was mainly caused by the broken of passive film and inter-phase corrosion, while wear-accelerated corrosion was the major contribution of synergy.Plastic deformation is hazardous to the corrosion resistance of high manganese steel, while it is the leading strengthen mechanism. Passivation deteriorates the wear resistance, while it is the most important way to enhance the corrosion resistance. Secondary phase strengthen is the leading mechanism of high chromium cast iron, but inter-phase corrosion deteriorates the wear resistance. The wear resistance and corrosion resistance conflict with each other to a certain extent. The corrosive wear rate will be minimized by optimizing the corrosive wear resistance of material or adjusting the service environment, by the means of quantifying the contribution of corrosive wear under the circumstance of real service. Finally, the physical model of corrosive wear mechanism on the two materials was proposed.