Study On The Preparation And Property Of Iron Oxide Coated Miro B₄C Powder

Boron carbide (B4C) is a superhard material which possesses the high hardness onlyafter diamond and cubic boron nitride. Composites prepared by B4C and bond are widelyused in grinding and cutting. However, there exites high interface potential energybetween B4C and the bond because of the unique structure and properties of B4C, whichresult in that B4C particles cannot be held by bond tightly and would be pulled out duringworking easily. Otherwise, B4C particles are easily oxidated during hot treatment whenB4C tools are fabricated, which decrease the processing quality as well as working life ofthe tools. In this paper, B4C was coated by a transition layer which not only combines B4Cand the bond but also protects B4C from corrosion by oxygen medium in the bond.B4C coated by iron oxidate was prepared by urea precipitation method. Studies haveshown that: uniform coating on B4C powders with an average particle size of40μm wasobtained when the concentrations of FeCl3and urea are respectively0.05mol/L and0.15mol/L. XRD, FESEM and DSC-TG were used to analyze the samples. Results show that:the precursor of the coating was FeOOH. Fe2O3coating was obtained at500C for2h,which was composed by massive nanorods with some fissures on, the thickness of theFe2O3coating was about250nm; it was turned out to be that the ingredient of the coatingwas FeB, Fe and B2O3after calcination at700C for2h under vacuum condition, and thecoating was composed by nano blocky-shaped particles, which was uniform and with nofissure.We prepared iron oxidate coating on3.5μm B4C by microwave assistance method.XRD showed that the precursor of the coating was FeOOH and the ingredient of thecoating we obtained was FeB and Fe after calcination at1000C for2h under vacuumcondition. FESEM showed that the coating after calcination was composed by nanoblocky-shaped particles.Vitrified bond B4C composites were prepared by Fe2O3coated B4C powders andSiO2-B2O3-Al2O3glass powders, and metal bond B4C composites were prepared by FeB,Fe and B2O3coated B4C particles and copper coated iron powders. The bending strengthof the two composites was respectively increased by14.4%and17.6%. FESEM showed that the coated B4C could combined with bonder more tightly than bare B4C, and thecoating can protect B4C also.