Research On High Chromium Cast Iron Used For Blade Of Shot Blasting Machine

Blade is the most easily worn part of shot blasting machine and its service life affects blasting efficiency. Due to its excellent wear resistance, high chromium cast iron is regarded as the ideal material of shot blasting machine blade. This subject is implemented under laboratory conditions. To begin with, effects of carbon content and molding sand on the microstructure and properties were investigated in order to determine the appropriate composition and cooling conditions. Then two methods were adopted to improve the microstructure and properties of high chromium cast iron. The first method was modification treatment by adding titanium element. The second method aimed at the actual working condition of the blade. The shots were under the force of friction when sliding on the blade. So a certain amount of self-lubricating element was added and effects of sulfur on the tribological properties of high chromium cast iron were studied.The results show that hypereutectic high chromium cast iron is the most wearable one, followed by eutectic composition, and hypoeutectic composition is the least resistant one in the dry sand rubber wheel abrasion test. Under the same conditions, specimens prepared by chromite sand present better wear resistance than those of quartz sand as molding material.A certain amount of titanium was added to improve the toughness of high chromium cast iron. Results show that titanium is easy to react with carbon and nitrogen to generate titanium compounds with high melting point. On the one hand, titanium compounds can be used as the nucleation substrate of carbide, on the other hand, they can prevent the austenite grain from growing up. Titanium plays an important role in refining the microstructure and improving the hardness, toughness and wear resistance of high chromium cast iron.After the addition of sulfur, morphology, composition of sulfide and friction and wear surface of the specimen were analyzed. Results show that sulfides of high chromium cast iron mainly present in the form of multi-angular, spherical, dendritic and crosswise shape. Morphology of sulfides varies with sulfur content. With the increase of sulfur content, the average friction coefficient and wear rate increase at first and then decrease. When0.25%sulfur was added, the sulfides were so small that they were easy to fall off from the surface, which increased the wear loss. However, when0.75%sulfur was added, the average friction coefficient and wear rate were much lower than those of specimen without sulfur. After friction wear, peeling pits appear on the surface of high chromium cast iron specimen without sulfur. While a layer of relatively homogeneous sulfide form on the surface of high chromium cast iron specimen with sulfur, which can slow down the wear of matrix and carbides to some extent.