Effect Of Nb And Cr On Microstructure And Wear Resistance Of Austenitic Ductile Iron

Austenite nodular iron is a kind of nodular iron with austenite structure,which is composed of acicular ferrite and high carbon austenite.Compared with the ordinary ductile iron,the Austenitic Ductile iron has many advantages,such as high strength,good plasticity,dynamic load,wear resistance,good shock absorption and so on.In this paper,the microstructure and properties of the nodular cast iron were studied by Nb and Cr alloying,and the mechanism of the two alloying effects on the wear resistance of the nodular cast iron was analyzed.The experimental process is to prepare different Nb and Cr contents of austenite nodular iron under the same isothermal quenching heat treatment parameters,which is divided into NB experimental group and Cr experimental group.The Nb experimental group is divided into three different content comparative experimental groups,which are A0: wt(Nb)= 0%,A1: wt(Nb)= 0.1%,A2: wt(Nb)= 0.25%,A3: wt(Nb)= 0.4%.The Cr experimental group is divided into three different content contrast experimental groups,which are B0: wt(Cr)= 0%,B1: wt(Cr)= 0.2%,B2: wt(Cr)= 0.4%,B3: wt(Cr)= 0.6%.Through the comparative analysis of the metallographic structure of the sample before and after wear and the wear experiment test,the experimental data are obtained to analyze the rule.The as cast structure of ADI is mainly composed of graphite,pearlite,carbide and a small amount of ferrite.Nb and Cr mainly exist in the form of carbides.Nb and Cr can affect the uniformity of graphite balls and the volume fraction of pearlite and carbides in the as cast structure.The higher Nb content is,the more uneven graphite distribution is,the more pearlite and carbide content is.The higher Cr content is,the smaller the size of graphite ball is,the smaller the volume ratio is,and the higher the content of pearlite and carbide is.The matrix structure of austenite nodular iron is mainly composed of acicular ferrite and high carbon austenite.The content of retained austenite in the matrix causes the work hardening effect of Nb and Cr containing austenite ductile iron samples when they are under stress during wear,which increases the surface hardness of the samples.Improve the wear resistance of the material.The wear test data of Nb alloyed austenite ductile iron samples show that when the Nb content is 0.25%,the wear amount is the smallest,so the wear resistance is the best.With the addition of Nb,the wear of the sample increases gradually.Through the observation of wear morphology,it is found that when the Nb content is 0.1%,the main failure modes of materials are abrasive wear and micro peeling;when the Nb content is 0.25%,abrasive wear is the main failure mode of materials;when the Nb content is 0.4%,abrasive wear and micro peeling are the main failure modes of materials.The wear test data of Cr Alloyed ferrites show that with the increase of Cr content,the wear amount decreases continuously,but the decrease range is decreasing.When Cr content is between 0.2% and 0.6%,wear and micro peeling are the main failure modes.