Preparation of (W,Mo)C/Al₂O₃/La₂O₃ composite powder by low temperature combustion method and its properties

Abstract

In order to develop a binderless phase cemented carbide to reduce the application of cobalt in conventional cemented carbides,(W,Mo)C/Al2O3/La2O3 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/Al2O3/La2O3powder.The (W,Mo)C/Al2O3/La2O3 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 0.28 μm 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%,2202HV30 and 1203 MPa,respectively,and the fracture toughness reaches a peak of 7.52 MPa·m1/2 at 1500 ℃. (W,Mo)C/Al2O3/La2O3 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/Al2O3/La2O3 is mainly intergranular fracture at 1700-1800 ℃ is grain growth and the appearance of pore.

Keywords

• (w,mo)c/al₂o₃/la₂o₃
• low temperature combustion method
• spark plasma sintering(sps)
• strengthening and toughening mechanism
• mechanical property