TABLE OF CONTENTS The use of inert additions to improve elevated temperature mechanical properties of metals was first exploited in 1910 by W.D. Coolidge in thoriated tungsten [1]. The development of dispersion-strengthened alloys by internal oxidation started in 1930 [2] and the invention of dispersion-strengthened aluminium took place in 1949 [3]. However, the relatively low melting point of aluminium was a severe limitation for the use of SAP at elevated temperatures. This led to attempts in applying dispersion strengthening to higher melting point metals such as copper and nickel.
In these metals, the self oxides cannot be used as they are not sufficiently stable against Ostwald ripening at elevated temperatures. ThO 2-dispersed nickel, having a finely distributed dispersoid, was produced successfully by melting to improve the mechanical properties (1960) [4]. The material has vastly developed elevated temperature properties. However, the use of such materials was still limited due to their low strength at intermediate temperatures and lack of corrosion resistance.
Hypothetically, these shortcomings could be solved by combining the corrosion resistance and intermediate temperature strength of ?'-precipitation-hardened, nickel-base superalloys with the high temperature strength and stability of oxide dispersion strengthening. One of the primary hurdles to materialize this idea is the production of uniform dispersion of fine oxide particles, less than 0.1 ?m in size, in alloy powder particles in such a manner which leads to interparticle spacing of less than 0.5 ?m in a consolidated product. The nickel-base superalloys contain chromium, aluminium and titanium for effective...
