Study on the Weldability of Ni Base Super Alloy (Part 4)

Messurement of the Initial Local Melting Temperature of Inconel 713C by Microscopic Observation

Abstract

Weld crackings of Inconel 713C were initiated at grain boundaries. These weld crackings are considered to be the same kind of hot crackings as repoted on the other Ni base super alloys.
Inconel 713C being a cast alloy, the alloying elements in it are easy to segregate. at grain boundaries and dendrite boundaries. Segregated elements are helpful to form low melting point particles.
Consequently, it is important to identify the location and temperature of local melting and thereby clarify the causes of weld crackings.
According to the microscopic observations of the same area before and after rapid heating in the vacuum, the temperature of local melting recognized in Alloy V-3 (low carbon Inconel 713°C), is particularly low compared with the other alloys, i.e., about 1235°C.
In Alloy V-3, a massive "White Constituent" exists at the grain boundaries and dendrite boundaries, and a fine "White Constituent" is formed continuously at the grain boundaries. The melting point of this constituent is lower than that of matrix.
It is considered that the "White. Constituent" is one of the causes of the weld crackings of Inconel 713C.