低温燃烧法制备(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)复合粉末及性能

Preparation of(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3) composite powder by low temperature combustion method and its properties

为了开发出一种无黏结相硬质合金来减少传统硬质合金中钴元素的应用,采用化学法制备(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)。以偏钨酸铵、钼酸铵、硝酸铝、硝酸镧、尿素和葡萄糖为原料,通过低温燃烧法探究硝酸盐和尿素、葡萄糖的不同配比,得出最优配比后还原炭化制备(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)粉末。在1500~1800℃经离子烧结制备(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)无黏结相材料,研究其力学性能并分析强韧化机制。结果表明:硝酸盐和尿素的最佳摩尔配比为1∶2,硝酸盐和葡萄糖的最佳摩尔配比为1∶0.5,加入葡萄糖后颗粒尺寸减小了0.28μm,比表面积提高了75.64%。致密度、维氏硬度和抗弯强度在1600℃时达到最大值分别为:98.45%,2202HV和1203 MPa,断裂韧度在1500℃时达到最大值为7.52 MPa·m^(1/2)。由于晶粒的细化及第二相颗粒的增韧的影响,(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)在1500~1600℃时以沿晶断裂和穿晶断裂为主;晶粒长大以及孔隙的出现导致(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)在1700~1800℃时以沿晶断裂为主。

In order to develop a binderless phase cemented carbide to reduce the application of cobalt in conventional cemented carbides,(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3) were prepared by chemical methods.Ammonium paratungstate,ammonium molybdate,aluminum nitrate,lanthanum nitrate,urea and glucose were used as raw materials to explore the different ratios of nitrate,urea and glucose by low temperature combustion method,and the optimal ratio of carbon was obtained to prepare(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3)powder.The(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3) binderless phase materials were prepared by SPS sintering at 1500-1800℃.The mechanical properties were studied and the strengthening and toughening mechanism was analyzed.The results show that the optimum molar ratio of nitrate to urea is 1∶2,the optimum molar ratio of nitrate to glucose is 1∶0.5,the grain size is reduced by 0.28μm after adding glucose,and the specific surface area is increased by 75.64%.Density,Vickers hardness and flexural strength reach maximum at 1600℃:98.45%,2202 HV30 and 1203 MPa,respectively,and the fracture toughness reaches a peak of 7.52 MPa·m^(1/2) at 1500℃.(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3) are mainly intergranular fracture and transgranular fracture due to the influence of grain refinement and toughening of the second phase particles at 1500-1600℃;the reason why(W,Mo)C/Al_(2)O_(3)/La_(2)O_(3) is mainly intergranular fracture at 1700-1800℃is grain growth and the appearance of pore.