Research And Developing Of A New Kind Of Cavitation Erosion Resistance Martensitic Precipitated Hardening Stainless Steel

Cavitation erosion is a normal phenomenon in water pump, screw, firebox and other hydro-machines. Cavitation is a process consisting of the repeated nucleation, growth, and violent collapse of bubbles in a liquid. The collapse impacts of the bubbles are so huge that flake material away from the surface. In order to lose the damage of cavitation erosion, a series of cavitation erosion resistance materials have been developed, including stainless steel, cobalt base alloy, copper base shape memory alloy. Many research show cavitation erosion resistance of metallic material depends on its stacking fault energy, phase transformation, second phase strengthen and microstructure. Martensitic precipitated hardening stainless steel is a kind of alloy with high strength and high tenacity. The strengthen mechanism includes martensitic dislocation tangle and second phase precipate. It was said some new kind of martensitic precipitated hardening stainless steel have been used for cavitation erosion resistance alloys in European counties and the property is excellent. So we have to develop our own martensitic cavitation erosion resistance stainless steel through learning the foreign research production and metal science.The alloy elements of new martensitic precipitated hardening stainless steel are Ni, Cr, Si, Mn, Cu, Mo, Nb. Because of the vacuum melting process and reasonable temperatures of solid solution and aging, new martensitic precipitated hardening stainless steel have high mechanical properties. And its electrochemistry corrosion resistance is excellent. Cavitation erosion test have been done by a ultrasonic vibratory apparatus according to ASTM G32/92. Through the test, Mass lost, metallographic photos and SEM photos have obtained. On account of second phase particles block dislocations, the distortion and fracture of martensitic plates are not easily done by cavitation. Finally lots of small fragments made by the fracture of the martensitic plates were peeling off. At the same time the incubation period of cavitation erosion was over. After 2h cavitation erosion test, Mass loss of this new martensitic precipitated hardening stainless steel is only 1/3 of Cu-Mn-Al. So this new martensitic precipitated hardening stainless steel can be well used, and have well market demand.