Microstructure And Wear Propertie Of FeWB Based Composite And Coating

Wear is one of the three main forms of engineering material failure,causing great economic loss in mining,metallurgy,agriculture,chemical engineering and machinery industry.Ternary boride combine with metal as a hard phase,becoming wear resistant composite or coating.It will improve the problem of wear failure in industrial manufacturing,due to their high strength,high toughness,strong oxidation resistance and good electrical conductivity.At present,the study of ternary boride based composite and its coating is not mature enough.It is necessary to develop new types of ternary boride and expand the research and application of ternary boride based composites in the field of wear resistance.In this paper,based on the basis of the research and application on the ternary boride based composites at home and abroad,a new ternary boride based composite containing FeWB and Fe was developed.And microstructure and wear resistance of FeWB based composite were analyzed.The main research results are as follows:(1)FeWB based composites were prepared via an infiltration casting process using gray cast iron as molten metal,W and B4C powers as raw materials.Composites are mainly composed of α-Fe,FeWB and WC,and a small number of Fe3(C,B).The in situ synthesized WC and FeWB were homogeneously distributed in the iron matrix,which significantly improves the wear resistance.The size and content of WC and FeWB increased with the increase of W content,which resulted in improved microhardness of composite,but gradually declined wear resistance due to the greater brittleness of the reinforcement and the weakened supporting effect of metal matrix to the reinforcement.(2)With the sintering temperature as variable,FeWB based composites were prepared via SPS using W,Fe,and Fe-B powers as raw materials.Sintering at low temperature(1000℃),the raw materials reacted hardly.The composite is mainly composed of raw material.With the increase of sintering temperature(1050℃),the atomic diffuse between adjacent powders,which resulted in generated a small amount of Fe2B,W2B and FeWB.Sintering at high temperature(1100℃),a large number of raw materials involve in the reaction,Fe2B and W2B disappear and transform into FeWB.The system reaction becomes more complete with the increase of the sintering temperature,which resulted in improved microhardness of composite,and the microhardness of area rich in FeWB is up to 1762 HV0.2.(3)FeWB coatings were prepared by spark plasma sintering on Q235 substrate using W,Fe,and Fe-B alloy powder mixture as raw materials,and they were subsequently treated by plasma re-melting at different currents.A poor mechanically bonding is obtained between the Q235 substrate and surface coating.The coating is composed of a large number of W and a little W2B,Fe7W6,FeWB.The segregation of microstructure is serious and many holes are formed As a result,microhardness and wear resistance are low.After re-melting at low current(30 A),the raw materials transform into FeWB further and the holes decrease.With the increasing of plasma re-melting current(40 A and 50 A),a transition layer between coating and substrate is formed.This is benefit to improve the bonding strengthening between surface coating and substrate to produce a dense and strong metallurgical interface.The FeWB are transformed from raw materials completely and unifornly distribute in α-Fe matrix.The denser coatings with higher microhardness are obtained.The wear resistance is significantly enhanced.Particularly,the re-melting coating at plasma current of 40 A shows excellent wear resistance.Its wear volume is only 17.4%of that of the SPS sintering coating.