| The main failure mechanism of components in farm machinery,mining,excavating equipment and shield machines is the frication and wear behavior,which results in resource delection annually.Therefore,developing a wear-resistant material with excellent performance to improve the service life of components is a scientific problem which should be solved urgently.WC/Fe composites are a type of wear-resistant materials which not only possess high hardness and high wear resistance of ceramic materials,but also possess good plasticity of metal materials.Several techniques have been used to prepare WC-reinforced Fe-based composites,such as infiltration casting technique,pressure sintering,pressure casting,and so on.There are some shortcoming exist in these methods,such as WC particle with unevenly distributed,Easy to form dendrite or fish bone eutectic carbide,contamination between reinforcements and matrix.Thus,WC/Fe composites with various WC contents were prepared by spark plasma sintering(SPS)in this work.The microstructure,phase composition and wear morphology were investigated with the help of the scanning electron microscopy(SEM),energy spectrums(EDS),X-ray diffraction(XRD)and transmission electron microscopy(TEM).The mechanical properties,tribological behavior of those materials and wear mechanism were investigated by nanoindentation,Rockwell hardness instrument,microhardness,three point bending test,pin-to-disc abrasive wear test.In order to enlarge the applied range of WC/Fe composites,a WC reinforced iron surface composites were produced by SPS and casting,and the microstructure and mechanical properties of the complex interface and surface layer were studied.The main results in this work are as follows:(1)The microstructure and phase constitution of the ex-situ and in-situ WC/Fe composites prepared by SPS showed that two kinds of composites materials were mainly composed of WC,ferrite,pearlite,Fe3W3C and a little W2C.Fe3W3C phase along[157]zone axis and Fe3C along[001]zone are observed.The(100)plane of the Fe3C is parallel to the plane(211)of the Fe3W3C phase.The content of Fe3W3C in ex-situ composites was higher than in-situ composites.Fe3W3C surrounded the WC particles(the thickness is less than 3 ?m),however,some of Fe3W3C spread throughout WC particles in ex-situ WC/Fe composites which increased the wear rate and reduced the wear-resistance.(2)The effects of WC contents were studied in this work,and results indicated that the hardness of the in-situ WC/Fe composites was affected by the WC contents.The phase constitution of the composites was not affected by the WC contents.The macrohardness of in-situ WC/Fe composites and the microhardness of their matrix phase were increased as the WC content increased.(3)The wear resistance of the in-situ WC/Fe composites was affected by the WC contents.The specific wear rates were decreased as the WC content increased.As the WC content varied within 32-42 vol%,the WC content had little affected on the specific wear rate.(4)The wear surface of composite were covered with a loosened surface film and grooves along the direction of sliding;the range of friction coefficient of the two kinds of composites varied widely range,indicating that the wear mechanism may be gradually changed from a two-body to a three-body abrasive wear scenario;the oxygen content in the wear surface were also determined by EDS and XRD.(5)WC reinforced iron based composites were prepared on a surface of 45 steels by means of SPS and casting.Result showed that the pouring temperature was 1748?1848 K.The 45 steels and WC/Fe composites with mass ratio of 10:1 to 14:1 were selected.The surface composite of 45 steels was treated by quenching(at 1178 K for 40min)and tempering(at 898 K for 2h).The hardness of tempered surface composites was lower than the original surface composites.Compared with 45 steels,the tempered surface composites had excellent wear resistance. |
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