New High-strength Stainless Steels

Abstract

A COMMON method of producing high creep strength in metals is to introduce a second, dispersed, phase to act as an obstacle to the motion of dislocations. At large volume fractions of the second phase this simple method gives very large increases in strength. Another important feature of high-temperature alloys, however, is that their strength should be retained for the duration of their service life, and this implies that the second phase particles must be resistant to coarsening. This is a very stringent condition and the most effective way of meeting it seems to be to use a dispersed phase with a very large negative free energy of formation. This is the basis of alloys such as sintered aluminium powder (SAP) and thoria dispersed nickel (TD nickel).