Cavitation Erosion Resistances of Cast Iron and Chromium Films Plated on Cast Iron under Various Conditions

Abstract

It is well known that pitting has often occurred on the water side of water cooled diesel cylinder liners. There has been but scanty record of studies made of the interrelations of cavitation erosion, the microstructure of cast iron, the hardness of chromium films plated on cast iron and the hardness of base metals studied.The present study was made with the aim to prevent pitting and to make clear the mechanism of cavitation erosion of cast iron and such chromium films. The magnetostrictive cavitation tests were carried out on specimens that are chromium films with various hardness plated on cast iron, various heat treated cast iron, chromium films with same hardness plated on various heat treated cast iron, carbon steel and chromium films plated on carbon steel.The results obtained are as follows(1) The high cavitation erosion resistance was obtained with plated chromium films of hardness between 850 and 900 Vickers hardness on specimens of chromium films with various hardness plated on cast iron.(2) The cavitation erosion resistance of cast iron increased with increasing hardness of cast iron. It seems that at first the cavitation erosion in the portion with graphite structure was caused by impact stress when cavities collapse, secondly the cracks grew up between graphite and graphite, and finally the destruction occurred.(3) The cavitation erosion resistance increased with increasing hardness of cast iron for specimens of chromium film with 874 Vickers hardness plated on various heat treated cast iron.(4) The high cavitation erosion resistance was obtained on specimens of chromium film plating on carbon steel.