Cast Structure in Alloy A286, an Iron-Nickel Based Superalloy

Frisk Frisk,Rogberg Rogberg,Andersson Andersson

doi:10.3390/met9060711

Abstract

The structure and segregation of a continuously cast iron-nickel based superalloy were investigated. Cross-sectional samples were prepared from the central section of a 150 × 150 mm square billet. The microporosity was measured from the surface to the center and theoretical conditions for pore formation were investigated. A central porosity, up to 10 mm in width, was present in the center of the billet. The measured secondary arm spacing was correlated with a calculated cooling rate and a mathematical model was obtained. Spinel particles were found in the structure, which acted as inoculation points for primary austenite and promoted the formation of the central equiaxed zone. Titanium segregated severely in the interdendritic areas and an increase of Ti most likely lead to a significant decrease in the hot ductility. Precipitates were detected in an area fraction of approximately 0.55% across the billet, which were identified as Ti(CN), TiN, η-Ni3Ti, and a phosphide phase.

Highlights

The austenitic stainless steels are the most commonly produced group of stainless steels.The stability of the mechanical properties of austenitic stainless steels makes them suitable for high-temperature applications, as well as for cryogenic applications [1]
The A286 steel alloy is an iron-nickel based austenitic superalloy with a Ti content of 2 wt % to promote a uniform formation of strengthening precipitates [2]
Open porosity and distinct V-segregation pattern are seen along the center line

Summary

Introduction

The stability of the mechanical properties of austenitic stainless steels makes them suitable for high-temperature applications, as well as for cryogenic applications [1]. Due to their face-centered cubic crystal structure, they are ductile even at extremely low temperatures. They have a good corrosion resistance due to their high chromium content. The A286 steel alloy is an iron-nickel based austenitic superalloy with a Ti content of 2 wt % to promote a uniform formation of strengthening precipitates [2]. The finished products are strengthened mainly by precipitation of γ’-Ni3 (Al,Ti) [3] after a heat treatment carried out at temperatures between

Methods

Results

Discussion

Conclusion