Distribution Characteristics of Inclusions in GH4742 Superalloy Ingot by Vacuum Arc Remelting

Abstract

A ϕ570 mm alloy ingot was utilized as the electrode for vacuum arc remelting， and a ϕ660 mm vacuum arc remelting ingot was prepared through the three stages of arc initiation， stabilized melting， and thermal capping. The melting process lasted a total of 860 minutes.The distribution of inclusions in the industrial ingot of vacuum arc remelting GH4742 alloy and its characteristic positions （crown， shelf and skin） was analyzed by field emission scanning electron microscope and inclusion automatic scanning system. The results of the study showed that there were four main types of inclusions in GH4742 alloy vacuum arc remelting ingots， including Ti（C，N）， LaAlO3-Ti（C，N）， Ti（C，N）-（Ti，Nb，Mo）C， and LaAlO3-Ti（C，N）-（Ti，Nb，Mo）C. The size of inclusions was mainly dominated by small-sized inclusions less than 3 μm. From the center to the edge， the size of inclusions gradually decreased and the number density gradually increased. The largest size of inclusions was observed at the middle center of the ingot， with a maximum average size of 4.14 μm. The lowest number of inclusions was observed at the bottom center of the ingot with a number density of 13.23 N/mm2. The aggregated oxide inclusions were distributed in the ingot crown， skin and shelf， which were formed when the oxides dislodged from the electrodes move to the edges of the ingot under the action of the flow field of the molten pool and are captured by the solidified regions at the edges.

Keywords

• gh4742 alloy； vacuum arc remelting （var）； impurity element； inclusion