EFFECT OF CHEMICAL COMPOSITION ON THE EROSION-CAVITATION RESISTANCE OF SURFACING MATERIALS OF Fe-Cr-C SYSTEM FOR HYDROTURBINE

In order to find an erosion-cavitation resistant material for hydroturbine,surfacing materials of Fe-Cr-C system were studied and evaluated in the laboratory with rota-ting blades type erosion-cavitation test apparatus which was designed and made by our-selves.Test results show that the ability of surfacing material to resist erosion-cavita-tion is essentially dependent on the quantity of primary chromium carbide in the microconstituents.Decreasing the carbon and chrome content in surfacing material would change the primary phase from chromium carbide,which is harder than eutectic,to alloyed austenite,which is softer than eutectic.Therefore,it would also lower the har-dness and the erosion-cavitation resistance of surfacing material.Further decreasing the carbon content would further lower the hardness and the erosion-cavitation resistance due to the decrease of eutectic and increase of austenite.The effect of B on the erosion-cavitation resistance of surfacing layer of 1.15%C,12%Cr steel electrode is more pronounced than on that of high carbon,high chrome white iron electrode.To increase the boron content in 0.1%C,13%Cr steel electrode would almost linearly increase the hardness and the erosion-cavitation resistance of surfacing material.