Search

Latest News

For all the latest news and features, sign up to receive our FREE updates by email:




Your Privacy

Particle precipitation phenomena

Posted on 10. April, 2012.

Bookmark and Share

Intense precipitation that occurs in high-temperature materials during service significantly affects their mechanical properties. This phenomenon in austenitic steel is investigated from two perspectives in the latest issue of Materials at High Temperatures.

Doi: 10.3184/096034012X13269825057728
Doi: 10.3184/096034012X13269748502792

Influence of particle formation during long time ageing on mechanical properties in the austenitic stainless steel 310

Rolf Sandstroma*, Muhammad Farooq(a) and Bo Ivarsson(b)

(a)Materials Science and Engineering, Royal Institute of Technology, Brinellv. 23, 100 44 Stockholm, Sweden

(b)Outokumpu Stainless R&D, 774 22 Avesta, Sweden

E-mail: rsand@kth,se

Intense precipitation may occur in high-temperature materials during service. This precipitation significantly affects the mechanical properties. Coarse precipitates can reduce ductility and toughness dramatically. To investigate the phenomenon, precipitation in the austenitic stainless steel AISI 310 is quantified in a parallel paper. The samples were aged up to 5000 h at 800OC. Especially, -phase and M23C6-carbides were analysed. A model for the influence of coarse particles on ductility has been developed and successfully applied to the measured values. A model due to Chen and Mott has been used to compute the effect of particles on toughness. A satisfactory agreement with the observations was obtained.

Keywords: austenitic stainless, long time ageing, elevated temperature, precipitation, ductility, toughness

From a technical point of view the results are of great value. They make it possible to predict the ductility and toughness in service exposed material. The amount of particles can easily be determined also for components still in service with non-destructive methods such as replica techniques. In combination with the models developed for computing the volume fraction of precipitated phases, the ductility and toughness models can be applied in the design of new steels.

DOI: 10.3184/096034012X13269825057728

Precipitation during long time ageing in the austenitic stainless steel 310

 Muhammad Farooq(a), Rolf Sandstroma* and Mats Lundberg(b)

(a)Materials Science and Engineering, Royal Institute of Technology, Brinellv. 23, 100 44 Stockholm, Sweden

(b)Sandvik Materials Technology R&D, 811 81 Sandviken, Sweden

*E-mail: rsand@kth.se

Extensive precipitation can occur in high temperature materials during service. This is known to significantly affect the mechanical properties. To be able to study this phenomenon, particle formation in the austenitic stainless steel 310 has been quantified. In particular, s-phase and M23C6-carbides have been analysed. Specimens have been aged up to 5000 h at 800oC. The precipitation of the two phases has been modelled. The basis of the model is diffusion controlled growth. -phase shows a spherical growth and an M23C6 planar growth. The soft impingement of the diffusion zones with respect to both chromium and carbon is taken into account. The influence on mechanical properties is analysed in a parallel paper.

Keywords: austenitic stainless, long time ageing, elevated temperature, precipitation, thermodynamic modelling

Long term ageing of the austenitic stainless steel 310 at 800oC for up to 5000 h has been performed. The purpose has been to characterise and model the formation of coarser particles that can deteriorate ductility and toughness of the material. This is analysed in an accompanying paper Two casts with different nitrogen contents have been studied. Both casts have been investigated in coarse grained and fine grained conditions.

Doi: 10.3184/096034012X13269748502792