Densificação e microestrutura de um compósito W-20%Ag obtido a partir da moagem e redução do pó compósito APT-21,71%AgNO3 e sinterização com fase líquida

Abstract

W-Ag composite is a good choice of material that has a good balance of properties, such as a good electrical conductivity combined with a low dimensional variation of the material in face of temperature variations that may affect it depending on the intended work. . The difficulty of combining these properties is what makes the powder metallurgical manufacturing process an excellent way to obtain new materials from the combination of materials with mutual insolubility, such as tungsten and silver. High-energy milling, compression or powder injection molding and sintering procedures allow you to produce W-Ag composite materials that are impossible by other manufacturing methods. The purpose of this work is to obtain a W-20% Ag composite from the sintering of a powder compact obtained by the decomposition and reduction of an ammonium paratungstate (APT) and silver nitrate (AgNO3) powder prepared for 2 and 20 hours. in a high energy planetary mill. The compacts of both grounded powders for 2 and 20 hours were sintered at 900 and 1000 oC for 60 minutes under a hydrogen atmosphere. The heating rate used in all experiments was 10 oC / min. Increasing grinding time decreased particle size and increased phase dispersion of the composite powders. A more homogeneous microstructure with a density of 87.4% was produced when compacted powders ground for 20 hours were sintered at 1000 oC. In contrast, a more heterogeneous microstructure with a density of 66.4% was obtained with the 2-hour ground compacted sintered at 900 oC. A hardness of 477.2 ± 29.8 HV was also obtained by sintered compacts under higher temperature and grinding time, while for sintered compacts under lower temperature and grinding time the hardness reached only 202 ± 11.7 HV.