The Preparation And Properties Of Ternary Boride Mo₂ FeB₂ Based Cermets

Ternary boride based cermets have excellent properties of mechanical,abrasive resistance,corrosive resistance and high temperature resistance.So it is widely used inindustry and agriculture and plays a very important role.The institution of ternary boride based cermets is in minority countries in the world such as Japan and America.They focused in the sintering properties and knew very few about the high temperature performance and corrosion resistance.In this dissertation,Mo₂FeB₂ based cermets were obtained by vacuum liquid phase sintering.The composition and structure of cermets were investigated by means of X-ray diffraction(XRD) and scanning electronmicroscope(SEM).The chemical composition of bonding phase and hard phase were investigated by energy spectrum.Some conclusions were drawn as follows:Mo₂FeB₂ based cermets are made up of Mo₂FeB₂ hard phase andα-Fe bonding phase.The alloy elements Ni enter into the bonding phase, One part exists as simple substance, and the other part mixs with Fe and forms alloy Ni-Fe.Elements Cr gets into both bonding phase and hard phase.According to my research on Mo₂FeB₂ based cermets, oxides such as MoO₃,Fe₂O₃,NiO,Cr₂O₃,which are formed under the temperature of 750℃.The relationship between oxidation weight gain and time obey parabolic dynamics equation when only adding Ni. At the same time,with the increase of its containing,oxidation rate will improve while its high temperature oxidation resistance will decrease.Adding Cr element,oxidation weight gain will not change clearly, while oxidation rate will decrease as the increasing of Cr.Corrosion resistance of Mo₂FeB₂ based cermets takes a good function in Sulfuric acid (5percent),and is serious in nitric acid-hydrofluoric acid.While it take an replacement reaction that is a lay of red copper covering its surface in sulfate-copper sulfate,which made it more difficult to be corroded.