Study On Structure Features And Strengthening Mechanism Of Wear-resistant Martensite And Bainite Dual-phase Grey Cast Iron

The structure features, strengthening machenism and wear resistance of martensite/bainite(M/B) dual-phase grey cast iron have been studied in this article. To make full use of high performance of M/B dual phase, influences of deflating and cutting actions introduced by flake graphites should be reduced as much as possible at first.Taking actions of reducing the conent of C and Si, adjusting the proportion of Si/C, adding anti-graphitizing elements such as Mn and Mo, adopting good inoculation and adding iron chill to increasing cooling rate in the course of casting, all of which could reduce quantities of flake graphites, passivate sharp corners. On the basic of above actions, taking special heat-treatment to Cr-Mu-Cu and Ni-Mo two kinds of low-alloying grey cast iron to get M/B dual phase. The result showed: there were some"white-bright zone"composing by retained austenite and high-carbon martensite in the M/B dual-phase matrix. The type of bainite gotten in the experiment was lower bainite. The first nucleation site of bainite was interface between flake graphite and austenite. The austenite along the direction of flake graphite sharp corner was also tending to transform into bainite. The next site easy for bainite nucleation was the boundary of austenite, also was the boundary of"white-bright zone", which transformed at a lower temperature.Using pressing-in method to explore the initiation and extension of cracks in M/B dual-phase grey cast iron, the result of stereoscan photographs showed: Crack first nucleated in the interface of G-m, Increasing pressure, it began to increate inside of"white-bright zone". M/B dual phase can strengthen the G-m interface. The crack nucleated in the G-m interface would prior to extend along G-m interface. Increasing pressure, the crack will go into the matrix and extend asthe shape of"Z".The static three-body grinding abrasions of M/B dual-phase grey cast iron also were explored in this artical. GCr15 and 45 steel two different materials were chosed as counterposing disk The wearing appearance and wearing mechanism under different working parameters have been studied.