The Effect Of Y Addition On The Microstructure And Mechanical Properties Of Mo₂FeB₂-based Cermets

The Mo₂FeB₂-based cermets were composite material composed by Mo₂FeB₂ as hard phase and Fe as binder phase.The Mo₂FeB₂-based cermets have excellent application prospects in tool and structural material due to the advantages of both metal and ceramic.It is important application to be cladding materials on the die steel.However,problems still exsisted like heterogeneous microstructure and mechanical properties.The effects of Y on the microstructure and mechanical properties of Mo₂FeB₂-based cermets,prepared by Spark Plasma Sintering,were investigated by adding different amounts of rare earth-Y element into the raw material.On the other hand,the Mo₂FeB₂-based cermets were deposited onto the H13 substrates with two different kinds of proportion of raw materials by Spark Plasma Sintering process.The microstructure,hardness of cross section and wearing resistance were investigated.The results are presented as followed.On one hand,it was found that the Y element is mainly located at the grain boundaries of Mo₂FeB₂-based cermets.The Y element could purify the grain boundaries by absorbing the impurities in it,which would inhibit grain boundary migration and restrain the grain growth;a small amount of Y element would dissolve in the Fe binder phase,which would change the structure of Fe.Different solubility of Mo in the Fe were obtained due to different structure of Fe,which resulted in different wettability of Fe binder phase on the Mo₂FeB₂ hard phase.Suitable content?1.00wt%-2.00wt%?of Y addition into the raw material would effectively improve the wettability of Fe binder phase on the Mo₂FeB₂ hard phase,which decreased the porosity of the Mo₂FeB₂-based cermets and the grain size of Mo₂FeB₂ hard phase.On the other hand,more amounts of Mo₂FeB₂ hard phase,homogeneous microstructure and small grain size resulted in high hardness,great toughness and excellent wearing resistance of the Mo₂FeB₂-based cermets.On the other hand,it found that the microstructure of the coatings,however with finer grains and more homogeneous microstructure,is extremely similar to that of Mo₂FeB₂-based cermets with 2.00wt%Y.the H13 substrates closed to the interface between the coatings and H13 substrates were strengthened due to the diffusion of alloy elements?Y,Mo,etc.?.The properties of H13 substrates were also improved by Spark Plasma Sintering,resulting in gentle gradient transition of hardness.The Mo₂FeB₂-based cermets gradient coatings were good for improving the surface performance of H13 substrates.