烧成与使用气氛对磷酸盐结合铬铝锆砖结构与性能的影响

Effects of firing and operating atmospheres on microstructure and properties of phosphate bonded Cr_2O_3-Al_2O_3-ZrO_2 bricks

首先研究了在空气中和埋炭条件下烧成时磷酸盐结合铬铝锆试样结构与性能的变化,然后探讨了在模拟使用气氛中二次处理后试样性能的变化,比较了空气中和模拟使用气氛下试样的抗侵蚀性能并分析了现场使用后铬铝锆砖的显微结构。结果表明:烧成气氛对磷酸盐结合铬铝锆砖结构与性能影响显著。空气中烧成时,磷酸盐能与氧化铬和氧化铝形成复合固溶体,提升材料的强度。埋炭条件烧成时,磷酸盐和部分氧化铬发生还原反应并生成一定量气相物质,材料基质中气孔数量和孔径明显增加,影响了氧化铬骨料与基质的结合,降低了材料的结合强度。使用过程中,铬铝锆砖边缘的磷酸盐和部分氧化铬在还原气氛下也会发生还原反应,使边缘的气孔数量及孔径明显增加,其抗侵蚀性能明显低于在空气中的抗侵蚀性能。

The microstructure and properties of phosphate bonded Cr2 O3-Al2 O3-ZrO2 specimens fired in air or coke bed were investigated firstly.Then property change of the Cr2 O3-Al2 O3-ZrO2 bricks after seconda-ry treatment in simulation environment was studied.Finally,corrosion resistances of the Cr2 O3-Al2 O3-ZrO2 bricks in air and simulation environment were compared;and microstructure of on-site used Cr2 O3-Al2 O3-ZrO2 bricks in slagging gasifiers was analyzed.The results show that the atmosphere produces significant effect on the microstructure and properties of the phosphate bonded Cr2 O3 -Al2 O3 -ZrO2 bricks.As the specimens are fired in air,the phosphate forms a composite solid solution with Cr2 O3 and Al2 O3 ,therefore strength of the specimens is enhanced.For specimens fired in coke bed,a certain amount of gases are generated owing to the reduction reaction of phosphate and part of Cr2 O3 ,which results in the increase of number and size of the pores,bad interfacial bonding between Cr2 O3 aggregates and matrix as well as low strength of the specimens.During service process in reducing atmosphere,the phosphate binder and part of Cr2 O3 in edge of the specimens are also reduced,leading to significant increase of number and size of the pores in the edge of the specimens;as a result,in reducing atmosphere,the specimens show much worse corrosion resistance than in air.