Effects of boron on microstructures and wear resistance of Fe-Cr-C system hardfacing alloys

Fe-Cr-C based hardfacing alloys were produced by the CO₂ gas shielded welding process utilizing the flux cored wires of 1.6 mm in diameter on low-carbon steel substrates. The hardfacing alloys contained the carbon contents in the range of 1.0%-3.0%,chromium contents of 15%-25%,boron contents of 0%-2.0%. The effects of boron carbide contents on the microhardness and wear resistance of the hardfacings were studied. The results show that the hardness increased from 57.1 HRC to 65.2 HRC as the boron contents reaches up to 2.0%. Compared without boron addition,the hardness increases by 14.2% times. The relative wear resistance increases from 3.5 to 18.0 times. By using of the optical microscope (OM),scanning electron microscope (SEM) and X-ray diffraction (XRD),the microstructures and distribution of carbides in the matrix were investigated. The microstructures of metallic matrix are composed by ferrite, austenite,(Fe,Cr)₇C₃,Fe₂B,etc. The additions of boron carbide in the wires can improve the microstructure of the matrix of the hardfacing alloys and the quantities of the carbides. The distribution of (Fe,Cr)₇C₃ particles are uniformly dispersed.