含硼高铬铸铁的组织及性能

在成分为2.7%C-17%Cr-0.7%M_0的高铬铸铁中设计了含硼量变化范围为0.1～1.2%的五种白口铸铁.考察了其铸态及热处理态的组织;进行了石英砂磨料和绿碳化硅磨料的三体磨损试验及湿式橡胶轮磨损试验;测定了材料的硬度、冲击韧性和断裂韧性.试验结果表明:硼促使化合物体积分数增加,并有新的硼碳化物形成;基体组织中铸态己有马氏体析出,具有更好的淬硬性;三体磨损石英砂磨料时随含硼量增加耐磨性显著提高,对碳化硅磨料则相反;在湿式橡胶轮磨损试验中约在0.9%B 处耐磨性出现了最大值;化合物量相近时,含硼与无硼高铬铸铁的韧性相当.

STRUCTURES AND WEAR RESISTANCE OF HIGH CHROMIUM CAST IRONS ALLOYED WITH BORON

Five white cast irons with a base composition 2.7% C-17% Cr-0.7% Mo containing various boron contents ranging from 0.1% to 1.2% are investigated in as-cast and heat-treated states.Two kinds of wear test are conducted: three-body wear test with silica sand or SiC abrasives,and rubber wheel wear test with silica sand-water slurry.Hardness,impact toughness and fracture toughness K_(?) are determined.Results show that boron increases the volume fraction of compounds and forms new bori(?) carbide;the as-cast structure exhibits better hardenability because martensite occurs;three-body wear resistance with silica sand increases considerably when boron content increases,while three-body wear resistance with SiC abrasives decreases with the increase of boron content;a maximum wear resistance in rubber wheel wear test appears st 0.9% B;the fracture toughness remains at the same level when the compound volume fractions are approximately the same in high chromium cast iron with or without boron.