球墨铸铁的汽蚀特性研究

针对球铁的汽蚀特性进行了研究,认为球铁中的石墨是球铁的汽蚀破坏源。汽蚀过程为:汽蚀冲击力首先击碎汽蚀面上的石墨并留下坑点和孔洞;孔洞底部基体组织发生变形以及汽蚀面下出现脱体现象;基体组织萌生裂纹;汽蚀裂纹扩展汇交形成层状剥蚀。球铁比普通灰铁具有较优的抗汽蚀性的主要原因,是由两种铸铁不同的石墨形状和结晶过程引起的。回火马氏体球铁具有最优的抗汽蚀性,脱体现象仅发生在1～2个共晶团的间距内,裂纹扩展受马氏体片的掉列方向影响;铁素体球铁具有最差的抗汽蚀性,在铁素体环中裂纹容易形成和扩展。提高球铁抗汽蚀能力的方法就是要消除铁素体环。

Investigation on the Cavitation Erosion of Nodular Cast Iron

An investigation on cavitation erosion of nodular cast iron is presented in this paper. It is considered that the graphites in nodular cast iron are main source of cavitation erosion. The erosion process is like this, first,the graphites on the erosion surface are attacked to pieces by cavitation stress so that pits and craters are left. Then the matrix and graphite are appeared under the erosion surface and cracks in the matrix structure initiate. Further,cracks in the matrix propagate and associate with each other to form cavitation erosion. In nodular cast iron, annealing martenic structure has best resistance and the decohe- sion appears only in the range of 1-2 grains. The ferritic structure has the worst resistance, cracks can easily initiate and propagate in ferritic screen. The way to improve cavitation erosion resistance of nodular cast iron is to eliminiate the ferritic screen and to increase the strength of the matrix structure.