Tests to Obtain Sintered Cr, Ni, Mo Alloyed Iron Base Materials, using Powder Metallurgy Processing

摘要

Starting from elemental powders iron-base materials containing 10-20 %wt Cr, 12-40 %wt Ni, 1-3 % wt Mo were obtained. Rectangular samples of 70 x 12 x h mm were obtained by pressing with 6 tf/cm~2 (600 MPa). The samples were pre-sintered in hydrogen atmosphere and then sintered hi argon atmosphere at 1255℃ from 2 hours. We had in view the sintering degree of materials prepared as a function of utilized size grain powders, the homogenization degree of the mixtures and their chemical compositions. The results show that the homogenization degree of the mixtures has a dramatic influence on the sintering way of these materials. The big grain size of the used chromium powders conducted to chemical and micro-structural nonhomogeneities. The chromium diffusion in the iron base matrix induced an internal tension in the matrix which was relaxed, especially by pores appearing at the adjacent zone of the chromium particles, and however at the grains boundaries. The microstructural nonhomogeneity caused by the big granulation of the used chromium powders and by the mixtures nonhomogeneity conducted to the poor mechanical properties, which were influenced by the structural nonhomogeneity, and by the pore presence. By using of the mechanical alloying processes, we appreciate that we can ameliorate the homogeneous mixtures quality and we can obtain microanocomposite powders consisting in element constituents microvolumes.