Self-Healing of Creep Cavities by Boron Segregation and Boron Nitride Precipitation Autonomously Developed during High Temperature Use

N. Shinya et al., "Self-Healing of Creep Cavities by Boron Segregation and Boron Nitride Precipitation Autonomously Developed during High Temperature Use", Materials Science Forum, Vols. 539-543, pp. 3145-3150, 2007

Online since:

March 2007

Authors:

Norio Shinya, Junro Kyono, Kinkar Laha

Keywords:

Creep Cavity, Creep Damage, Rupture Properties, Self-Healing, Stainless Steel (SS), Surface Precipitation, Surface Segregation

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References

[1] H. Trinkaus and H. Ullmaier: Phil. Mag., 39(1979), p.563.

[2] S. H. Goods and W. D. Nix: Acta Metall., 26(1978), p.739.

[3] W. D. Nix, K. S. Yu and J. S. Wang: Metall. Trans. A, 14A(1983), p.563.

[4] R. T. Holt and W. Wallace: Int. Met. Rev. 21(1976), p.1.

[5] R. W. Swindemann, U. K. Sikka and R. L. Klue: Metall. Trans. A, 14A(1983), p.581.

[6] K. Laha, J. Kyono, S. Kishimoto and N. Shinya: Scr. Mater., 52(2005), p.675.

[7] K. Laha, J. Kyono, T. Sasaki, S. Kishimoto and N. Shinya: Metall. Mater. Trans. A, 36A(2005), p.399.

Paper TitlePages

Microstructure and Creep Properties of AISI 316LN Steels with Niobium Additions

Authors: Vlastimil Vodárek, Gabriela Rožnovská, Jaromír Sobotka

Abstract: The long-term creep rupture tests have been carried out on three casts of a type AISI 316LN steel at 600 and 650°C. Two of the casts investigated contained additions of 0.1 and 0.3 wt.% of niobium. The growing niobium content strongly reduced the minimum creep rate and prolonged the time to the onset of the tertiary stage of creep and also shortened this stage. The enhanced creep resistance of niobium containing steels is not accompanied by the longer creep life that might have been expected. At both temperatures of creep exposure the niobium-bearing casts displayed an inferior creep ductility. Microstructural investigations revealed that niobium provoked significant grain size refinement and the formation of Z-phase. Particles of this phase were considerably dimensionally stable. Furthermore, niobium accelerated the formation and coarsening of s-phase, h-Laves and M6(C,N). The coarse intergranular particles facilitated the formation of cavities which resulted in intergranular failure mode.

275

Effect of Grain Boundary Serration on the Tensile Properties of the Super 304H Heat Resistant Austenitic Stainless Steel

Authors: Sung Min Hong, Dong Joon Min, Eric Fleury

Abstract: Grain boundary serrations were produced in heat-resistant austenitic stainless steel containing Cu by applying after solution heat-treatment a holding time in the range 700-800oC between 30 minutes to 3 hours. These special treatments provide an enhancement of the tensile ductility of about 40 and 113%at room temperature and 750oC, respectively, while no significant change in the yield stress and tensile strength could be observed.

170

A Comparative Study of Cavitation Erosive Behaviour of 23/8N Nitronic Steel and 13/4 Martensitic Stainless Steel

Authors: Ashish Selokar, D.B. Goel, Ujjwal Prakash

Abstract: Abstract: Hydroturbine blades in hydroelectric power plants are subjected to erosion. Currently these blades are made of 13/4 martensitic stainless steel (ASTM grade A743). This steel suffers from several maintenance and welding related problems. Nitronic steels are being considered as an alternative to martensitic stainless steels since they have good weldability. In present work, erosive behaviour of 13/4 Martensitic and Nitrogen alloyed austenitic stainless steel (23/8N steel) has been studied. Cavitation erosion tests were carried out in distilled water at 20 KHz frequency at constant amplitude. Microstructure of eroded surface, mechanical properties and erosion rate were characterized. It was observed that 23/8N steel possesses excellent resistance to erosion in comparison to 13/4 martensitic steels. 23/8N steel showed good hardness coupled with high tensile toughness and work hardening ability, leading to improved erosion resistance.

554

The Role of Post Service Heat Treatment on the Contributions of Creep Deformation and Fracture to Service Life of AISI Type 316H Steel Components

Authors: A.D. Warren, B. Chen, I. Griffiths, P.E.J. Flewitt

Abstract: Creep cavitation is a life limiting factor in stainless steel high temperature plant. However, regenerative heat treatments offer the potential of sintering creep cavities and thus extending a component’s time to failure. This is countered by thermal aging effects which can lead to precipitate formation and an increased creep rate. This study investigates these behaviours in a AISI Type 316H austenitic stainless steel.

247