THE PROCESS OF ELIMINATING PORES FROM TUNGSTEN HEAVY ALLOYS BY LIQUID PHASE SINTERING OF W-Ni

Abstract

Abstract: The study concerns the processes taking place in the liquid phase sintering of W-Ni. When we sinter fine powders of W and Ni, at first, Ni concentrates in the center of the sample, forming a high density area. This phenomenon occurs without any local density variation in raw and may be attributed to the decreasing tendency of the area of total liquid-vapors interface. After continuing the sintering, the dense area and Ni are dispersed towards the exterior, sometimes leaving behind isolated pores. The process of eliminating pores was studied using the large spherical pores artificially created by sintering the mixtures of Ni spherical particles and fine W powder. After prolonged sintering, these spherical pores are filled with liquid from the surrounding dense area. We found out that the liquid phase sintering of W-Ni takes place by concentrating the dispersed liquid from the dense area towards the exterior and by eliminating pores due to liquid flow.
Key words: Tungsten heavy alloy; liquid phase sintering; porosity.