ANISOTROPY OF DIMENSIONAL CHANGE AND ITS CORRESPONDING IMPROVEMENT BYADDITION OF TIH2 DURING ELEMENTAL POWDER SINTERING OF POROUS NITI ALLOY

The paper deals with the influence of TiH2 content and sintering condi tions (sintering temperature and sintering time) on the dimensional ch anges and the radial/axial shrinkage (R/A)-ratio of powder compacts. T he purpose was to try to find out how to make precision porous product s using a conventional powder metallurgical process. It was found that the dimensions of the compact shrink and anisotropy of dimensional ch ange (ADC) occurs during sintering. Addition of TiH2 markedly minimize s ADC and makes it possible to manufacture the desired final product s hape. An R/A-ratio less than 1 is supposed to be attributed to the dif ferences in the degree of mechanical deformation, which occurs on the surface of powder particles parallel to and perpendicular to the direc tion of pressing during the pressing process. A model of the pore chan ges during pressing and sintering is proposed. (C) 1998 Elsevier Scien ce S.A. All rights reserved.