High boron hardfacing alloys reinforced with primary M2B phases on Q235 steel plates were prepared by the method of flux-cored wire submerged arc welding. The microstructure and boride morphology were investigated usi...High boron hardfacing alloys reinforced with primary M2B phases on Q235 steel plates were prepared by the method of flux-cored wire submerged arc welding. The microstructure and boride morphology were investigated using optical microscopy （OM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The effect of WC/W2C on the microstructure was discussed. It indicated that the volume fraction of primary M2B phases has increased due to good nucleated cores of incompletely molten W2C particles provided by casting tungsten carbide or decarburizing reaction of WC powders. Abrasion resistance was evaluated by wet sand rubber wear tests and the wear mechanism was studied using SEM. It shows that primary M2B grains play a key role in improving abrasion resistance.展开更多
The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply ...The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply the elementary information about the existing form of B and Zr in the as-cast microstructure, which is helpful for the subsequent processing, such as homogenization treatment. The M_3B_2 and Ni_5Zr phases were observed in the U720 Li alloy in as-cast state, which were usually accompanying with each other together with g-Ni_3 Ti phase at the edge of eutectic（γ＋γ＇）. Combining the DTA analysis and heating and quenching tests, the solidification sequence was determined to be the following： c matrix, eutectic（γ＋γ＇）, g-Ni_3Ti, M_3B_2 and Ni_5Zr. The in situ composition analysis by EDS and EPMA revealed that the precipitation and microstructure were governed by the composition evolution in the liquids. The solidification of c matrix increased the Ti concentration in the residual liquids and resulted in the eutectic（γ＋γ＇） formation; the（γ＋γ＇） formation increased the Ti/Al radio in the liquids and the g-Ni_3Ti was formed in front of the eutectic（γ＋γ＇）; the g-Ni_3Ti precipitation consumed up Al and Ti and increased the concentration of B, Mo and Cr, and M_3B_2 boride is formed;the previous precipitation of the phases consumed up most of the elements other than Ni and Zr, and Ni_5Zr is formed finally. The melting points are in the ranges of 1130–1140 °C for Ni_5Zr phase, 1180–1190 °C for M_3B_2 boride and1190–1200 °C for g-Ni_3Ti phase.展开更多
基金supported by the Natural Science Foundation of Hunan Province,China(No.10JJ6078)
文摘High boron hardfacing alloys reinforced with primary M2B phases on Q235 steel plates were prepared by the method of flux-cored wire submerged arc welding. The microstructure and boride morphology were investigated using optical microscopy （OM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The effect of WC/W2C on the microstructure was discussed. It indicated that the volume fraction of primary M2B phases has increased due to good nucleated cores of incompletely molten W2C particles provided by casting tungsten carbide or decarburizing reaction of WC powders. Abrasion resistance was evaluated by wet sand rubber wear tests and the wear mechanism was studied using SEM. It shows that primary M2B grains play a key role in improving abrasion resistance.
文摘The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply the elementary information about the existing form of B and Zr in the as-cast microstructure, which is helpful for the subsequent processing, such as homogenization treatment. The M_3B_2 and Ni_5Zr phases were observed in the U720 Li alloy in as-cast state, which were usually accompanying with each other together with g-Ni_3 Ti phase at the edge of eutectic（γ＋γ＇）. Combining the DTA analysis and heating and quenching tests, the solidification sequence was determined to be the following： c matrix, eutectic（γ＋γ＇）, g-Ni_3Ti, M_3B_2 and Ni_5Zr. The in situ composition analysis by EDS and EPMA revealed that the precipitation and microstructure were governed by the composition evolution in the liquids. The solidification of c matrix increased the Ti concentration in the residual liquids and resulted in the eutectic（γ＋γ＇） formation; the（γ＋γ＇） formation increased the Ti/Al radio in the liquids and the g-Ni_3Ti was formed in front of the eutectic（γ＋γ＇）; the g-Ni_3Ti precipitation consumed up Al and Ti and increased the concentration of B, Mo and Cr, and M_3B_2 boride is formed;the previous precipitation of the phases consumed up most of the elements other than Ni and Zr, and Ni_5Zr is formed finally. The melting points are in the ranges of 1130–1140 °C for Ni_5Zr phase, 1180–1190 °C for M_3B_2 boride and1190–1200 °C for g-Ni_3Ti phase.
