Correlation between microstructure and cavitation-erosion resistance of high-chromium cast steel - preliminary results

Cavitation-erosion is a complex and highly localized phenomena involving mechanical, chemical and metallurgical parameters. The development of new materials depends on the understanding of the relationship between microstructure and cavitation-erosion, This paper investigates the role played by the microstructure on cavitation-erosion rates of 35Cr-25Ni-3Mo and 35Cr-8Ni-3Mo-2Nb, with and without tungsten addition in the as-cast condition. The difference in the microstructures was a consequence of distinct cooling rates due to the casting mold geometry. Metallographic techniques were used to reveal the microstructure. Cavitation tests were made by means of a vibratory apparatus. The performance of the alloys is compared with AISI 304 austenitic stainless steel. All alloys tested presented an improved performance when compared with the AISI 304. Alloys solidified with a high cooling rate presented best results and this behavior is attributed to the differences in the microstructure. For high-chromium cast steel, the increase of the austenite content decreases cavitation resistance. It was also observed that finer carbide particle morphology has a beneficial effect on the cavitation resistance of these materials. (C) 1999 Elsevier Science S.A. All nights reserved.