The Effect of Silicon and Iron on the Weldability of Ni-Co-Cr-Si HR-160® Alloy

Abstract

Solidification cracking of HAYNES HR-160®¹ alloy was investigated with an emphasis on the interactive effects between silicon and iron concentrations. The focus on silicon was relevant to its major role in the sulfidation and oxidation at elevated temperatures, while the focus on iron was to explore the potential use for over-lay welding onto alloyed steels. Five compositions of the alloy were investigated, covering a [2 × 2] matrix of low and high concentrations of silicon and iron, in addition to the commercial alloy. To find a relationship between thermodynamic properties, microstructures, and weldability, several supporting analyses were performed. These analyses were differential thermal analysis and electron microscopy (chemical analysis), as well as fractographic investigations. Within the tested levels of alloying addition, both silicon and iron additions proved to increase the susceptibility of the alloy to solidification cracking, with silicon having the predominant influence. The detrimental effect that silicon caused was the increase in the solidification temperature range of the alloy, which in turn increased the brittle temperature range of the alloys. On the other hand, iron has the tendency to decrease the threshold strain to cracking, even though it narrowed the brittle temperature range of the alloy for a fixed concentration of silicon.

¹ HAYNES and HR-160 are trademarks of Haynes International Inc.