An Experimental Study On The Erosion Mechanism In Power Station And The Anti-Erosion Performance Of Materials

The "four pipes" leaking of power boilers in coal-fired power plants greatly influence their safely and economically operating. Among these kinds of problems the leaking caused by flying-ash erosion on the contra-flow heated side covers sixty percentages. So the resolve of erosion problems is quite a subject in power boiler industry. There are lots of factors affecting erosion, among which the factor of materials matter a lot. In order to improve the anti-erosion performance of pipe materials, 20 Carbon steel and 12Cr1MoV alloy steel, the common materials used in contra-flow heated side of power boilers, have been carbonitrided and ionodialysized. Then they were tested by flying-ash erosion to find the possibility of improving the anti-eroding performance of materials through these two heat-treating methods.The results of testing demonstrated such achievements as follow:After the process of carbonitriding, the wear-resisting property of 20 Carbon steel increased and the wear extent reduced by more than half. The reason is C-N layer produced on the surface of 20 Carbon steel are rigid and not easy to be uncovered, which protect materials very well. The wear-resisting property of 12CrlMoV alloy steel has not changed. Wear extent was as much as the one without being heat treated, and even increased in high temperature stage. The reason is that the black remains of austenitic transmuted to non-marten site on the surface. These transmuting products made the structure and rigidity of alloy steel unsteady, which make the wear-resisting property unchanged. After plasma nitriding, the wear-resisting property of these two materials didn't change. Under the condition of below 490℃, the rate of wear is higher than that without being heat treated, and when over 490℃the rate is lower. This is because the nitration case on the surface of these two materials is thin and easy to break up after being brushed. And wear extent enlarged at the beginning.Deeper research shows that the structures of reticular and ribbon compound on the surface of 20 Carbon steel made the wear-resisting and fatigue-resisting properties low. And there existed different size blank pots in the structure of 12Cr1MoV alloy steel, which may be the main reason why the wear-resisting property declined.The conclusion from the research is that the surface hardness of two materials is also enhanced after Carbonitriding and Plasma Nitriding.However, which we can see from the experiment is that the enhancement in hardness can not always improve the wear-resistance of materials. The wear-resistance has relation to the performance of itsself,the condition of heat treatment,the surface of materials and so on.