The effect of single addition of such solid solution elements as W, Mo, Al, Mn and Cu on the creep and creep rupture properties of carbon free 17Cr-14Ni steel were studied at 700°C.
The steady state creep rate, ∈_s, was analyzed in terms of three factors, stacking fault energy, γ, elastic modulus, E, and diffusion constant, D, using a Sherby-Barrett equation: ∈_s=Aγm (σ/E) ⁿD, where A and σ are a constant and the applied stress, respectively, and m and n are fixed to 1 and 7, respectively, for application to the austenitic steels.
Since it was found that the effect of solute elements on the steady state creep rate of 17Cr-14Ni steels can not be analyzed only by the above three factors, the size effect of solute atoms was proposed as a fourth and important factor.
As a certification of this assumption, the linear relation between the lattice distortion induced by solute elements and logarithmic steady state creep rate was found experimentally.
It was concluded from these results that the size effect of solute atoms is the most important strengthening factor controlling the steady state creep rate of austenitic heat resisting steels.