The effect of tungsten on creep

The effect of tungsten on creep behavior and microstructural evolution was investigated for tempered martensitic 9Cr steels with various W concentrations from 0 to 4 wt pct. The creep rupture testing was carried out at 823, 873, and 923 K for up to 54 Ms (15,000 hours). The creep and creep rupture strength increased linearly with W concentration up to about 3 wt pct, where the steels consisted of the single constituent of the tempered martensite. It increased only slightly above 3 wt pct, where the matrix consisted of the tempered martensite and δ-ferrite. The minimum creep rate was described by a power law. The apparent activation energy for the minimum creep rate showed a tendency similar to the W concentration dependence of the creep-rupture strength and was larger than the activation energy for self-diffusion at high W concentrations above 1 wt pct. The martensite lath microstructure with fine carbides along lath boundaries was responsible for a high resistance to creep deformation. With increasing W con- centration, the martensite lath microstructure became stabilized, which decreased the minimum creep rate and increased the apparent activation energy for the minimum creep rate.

[1]  T. Noda,et al.  The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel , 1992 .

[2]  T. Noda,et al.  Microstructure and toughness of Cr?W and Cr?V ferritic steels , 1988 .

[3]  R. L. Klueh,et al.  Reduced Activation Materials for Fusion Reactors , 1990 .

[4]  Ronald L. Klueh,et al.  Development of ferritic steels for reduced activation: The US program , 1986 .

[5]  R. Tanaka,et al.  Creep Damage of 1Cr-1Mo-1/4V Steel , 1984 .

[6]  Takemi Yamada,et al.  Effects of Ta and Nb on Microstructures and Mechanical Properties of Low Activation Ferritic 9Cr-2W-0.2V Steel for Fusion Reactor , 1990 .

[7]  Tetsuji Noda,et al.  The effect of tungsten on dislocation recovery and precipitation behavior of low-activation martensitic 9Cr steels , 1991 .

[8]  R. Klueh.  Heat treatment effects on creep and rupture behavior of annealed 2.25 Cr-1 Mo steel , 1978 .

[9]  Ronald L. Klueh,et al.  Ferritic/martensitic steels: promises and problems , 1992 .

[10]  K. R. Williams,et al.  Effects of microstructural instability on the creep and fracture behaviour of ferritic steels , 1977 .

[11]  R. W. Evans,et al.  Creep of metals and alloys , 1985 .

[12]  D. Dulieu,et al.  The development of low-activation martensitic 9 and 11%Cr,W,V stainless steels for fusion reactor applications , 1988 .

[13]  A. Bowen,et al.  Solute diffusion in alpha- and gamma-iron , 1970 .

[14]  F. W. Wiffen,et al.  Optimizing materials for nuclear applications , 1985 .

[15]  Manabu Tamura,et al.  Development of potential low activation ferritic and austenitic steels , 1986 .

[16]  R. L. Klueh,et al.  The development of ferritic steels for fast induced-radioactivity decay for fusion reactor applications ☆ , 1985 .

[17]  W. Chen,et al.  The application of martensitic stainless steels in long lifetime fusion first wall/blankets☆ , 1979 .

[18]  M. Kikuchi,et al.  The Effect of Stress on Degradation of 1Cr-1Mo-1/4V Steel at Elevated Temperatures , 1986 .