MgO细粉加入量对Al2O3-Al-C不烧滑板材料性能的影响

Effects of MgO fines addition on properties of unfired Al2O3-Al-C slide plate materials

以板状刚玉颗粒与细粉、α-Al2O3微粉、金属Al粉、MgO细粉和石墨为原料,酚醛树脂为结合剂,在加入4%( w )Al粉基础上,用< 0.088 mm 的MgO细粉等量替代刚玉粉,研究MgO细粉加入量(质量分数分别为0、1%、3%和5%)对Al复合Al2O3-C不烧滑板材料性能、组成和显微结构的影响。结果表明:不加MgO细粉时,金属Al与C和N2反应生成纤维状Al4C3和AlN而起增强增韧作用,材料具有较高的高温强度和优良的抗热震性。MgO细粉加入量为1%( w )时,材料保持较高的高温强度和优良的抗热震性,材料中有较多纤维状Al4C3和AlN生成。MgO细粉加入量≥3%( w )时,材料的高温强度和抗热震性明显下降,这是由于MgO与基体中Al2O3以及Al反应生成的Al2O3发生反应生成MgAl2O4膨胀,进而产生较多裂纹,同时Al4C3和AlN生成量明显降低。但随着MgO细粉加入量的增加,材料的抗氧化性提高,这是由于在试样外层形成MgAl2O4致密层,阻碍氧气向材料内部扩散。

Tabular alumina particles and fine powder,α-Al2O3 micropowder,metal Al powder,graphite and MgO fines were used as the starting materials,and phenol formaldehyde resin as the binder.With 4 mass % of Al addition,the effects of MgO addition (< 0.088 mm ,0,1%,3% and 5%,by mass) to equivalently substitute for tabular alumina fines on properties,phase composition and microstructure of unfired Al composited Al2O3 - C slide plates were investigated.The results are indicated as follows.Without MgO fines,Al reacts with C and N 2 to form fibrous Al 4C 3 and AlN,which strengthens and toughens the material,and endows the material with high hot strength and thermal shock resistance.With 1% MgO fines,there are a lot of fibrous Al4C3 and AlN formed in the material and the material keeps excellent hot strength and thermal shock resistance.However,when the MgO addition is ≥3%,the hot strength and thermal shock resistance decrease noticeably.This is attributed to the reaction of MgO with Al 2O 3 from the matrix or from the oxidation of Al to form MgAl 2O 4,producing expansion and more cracks,and the formation of Al 4C 3 and AlN decreases greatly.The oxidation resistance of the material can be improved with the rising addition of MgO,which may be due to the dense MgAl 2O 4 layer formed in the out layer of specimens that retards O 2 diffusion into the specimens.