Estudo Do Mecanismo De Formação De Inclusões Não Metálicas Em Um Processo De Fundição – Resultados Preliminares

Abstract

Some austenitic alloys undergo a severe ductility drop at intermediate temperatures, which may result on the phenomenon known as ductility dip cracking (DDC). This solid state, intermediate temperature and intergranular cracking has been recognized as a grain boundary sliding phenomenon. This work studies the effect of Nb and Ti additions to Ni-base filler metals 52 and 82 on the DDC susceptibility. Ni-base filler metals 52 (0.25%Mn-8.9%Fe-29.1%Cr-0.5%Ti-0.7%Al-Ni) and 82 (2.75%Mn-0.7%Fe-20.1%Cr-2.6%Nb-0.5%Ti-Ni) with different amounts of Nb and Ti were prepared. The strain-to-fracture (STF) test was performed on the Gleeble system at 950 °C, to quantify the materials ductility. The samples were analyzed on the light microscope and SEM. An excessive addition of such elements to the weld metal caused solidification cracking. On the other hand, small additions have an appreciable beneficial effect on these alloys' DDC resistance. The improvement in DDC resistance is directly related with the GB morphology changes caused by the precipitates formed during solidification or at elevated temperature. These results provide new insight into the development of modified 52 and 82 DDC resistant filler metals.