Oxidation of Al-Co Alloys at High Temperatures.

Patrik Šulhánek,Marián Drienovský,Marián Palcut,Ramūnas Skaudžius,Libor Ďuriška,Žaneta Gerhátová,Ivona Černičková

doi:10.3390/ma13143152

Abstract

In this work, the high temperature oxidation behavior of Al71Co29 and Al76Co24 alloys (concentration in at.%) is presented. The alloys were prepared by controlled arc-melting of Co and Al granules in high purity argon. The as-solidified alloys were found to consist of several different phases, including structurally complex m-Al13Co4 and Z-Al3Co phases. The high temperature oxidation behavior of the alloys was studied by simultaneous thermal analysis in flowing synthetic air at 773–1173 K. A protective Al2O3 scale was formed on the sample surface. A parabolic rate law was observed. The rate constants of the alloys have been found between 1.63 × 10−14 and 8.83 × 10−12 g cm−4 s−1. The experimental activation energies of oxidation are 90 and 123 kJ mol−1 for the Al71Co29 and Al76Co24 alloys, respectively. The oxidation mechanism of the Al-Co alloys is discussed and implications towards practical applications of these alloys at high temperatures are provided.

Highlights

Co-based superalloys are promising materials for high temperature structural applications because of their high melting points and favorable mechanical properties [1,2,3]
The alloys were prepared by rapid solidification of alloy was composed of (Al) and Co lumps in argon
The alloys were studied in as-solidified state

Summary

Introduction

Co-based superalloys are promising materials for high temperature structural applications because of their high melting points and favorable mechanical properties [1,2,3]. Applications of these alloys include gas turbines, aircraft engines, and chemical reactors [4,5,6]. Cr form a compact chromia scale (Cr2 O3 ) on their surface. At high temperatures and high oxygen partial pressures, the Cr2 O3 scale is prone to degradation. During long-term oxidation, volatile high-valent oxides of Cr, such as CrO2 and CrO3 , start to form at the expense of Cr2 O3

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