Ferritic/martensitic steels for next-generation reactors

https://bura.brunel.ac.uk/bitstream/2438/13101/1/FullText.pdf

Cold spraying - A materials perspective

Cold gas dynamic spray or simply cold spray (CS) is a process in which solid powders are accelerated in a de Laval nozzle toward a substrate. If the impact velocity exceeds a threshold value, particles endure plastic deformation and adhere to the surface. Different materials such as metals, ceramics, composites and polymers can be deposited using CS, creating a wealth of interesting opportunities towards harvesting particular properties. CS is a novel and promising technology to obtain surface coating, offering several technological advantages over thermal spray since it utilizes kinetic rather than thermal energy for deposition. As a result, tensile residual stresses, oxidation and undesired chemical reactions can be avoided. Development of new material systems with enhanced properties covering a wide range of required functionalities of surfaces and interfaces, from internal combustion engines to biotechnology, brought forth new opportunities to the cold spraying with a rich variety of material ...

/pdf/cold-spray-coating-review-of-material-systems-and-future-587nnmmxb4.pdf

Cold spray coating: review of material systems and future perspectives

Besides the excellent high-temperature mechanical properties, Si3N4 and SiC based ceramics containing insulating or electrically conductive phase are attractive for their tunable dielectric propert...

Electromagnetic properties of Si–C–N based ceramics and composites

https://www.tandfonline.com/doi/pdf/10.1088/1468-6996/9/1/013002

Precipitate design for creep strengthening of 9% Cr tempered martensitic steel for ultra-supercritical power plants

Single-Crystal SiC Nanowires with a Thin Carbon Coating for Stronger and Tougher Ceramic Composites

The microstructural instability during creep and its effect on creep behavior were investigated for a martensitic 9Cr-2W steel. The steel was developed as a low radioactive steel suitable for fusion reactor structure. Creep testing was carried out at 873 K for up to 15,100 ks (4200 hours). The creep curve consisted of transition creep, where creep rate decreased with time, and acceleration creep, where creep rate increased with time. During creep, microstructural instability, such as the recovery of dislocations, the agglomeration of carbides, and the growth of martensite lath subgrains, was observed to occur, which resulted in softening but no hardening. The transition creep was a consequence of the movement and annihilation of excess dislocations, resulting in the decrease in dislocation density and the increase in martensite lath size with time. The acceleration creep was a consequence of a gradual loss of creep strength due to the microstructural instability which occurred from the initial stage of creep.

The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel

The effect of W on dislocation recovery and precipitation behavior was investigated for martensitic 9Cr-(0,l,2,4)W-0.1C (wt pct) steels after quenching, tempering, and subsequent prolonged aging. The steels were low induced-radioactivation martensitic steels for fusion reactor structures, intended as a possible replacement for conventional (7 to 12)Cr-Mo steels. During tempering after quenching, homogeneous precipitation of fine W2C occurred in martensite, causing secondary hardening between 673 and 823 K. The softening above the secondary hardening temperature shifted to higher temperatures with increasing W concentration, which was correlated with the decrease in self-diffusion rates with increasing W concentration. Carbides M23C6 and M7C3 were precipitated in the 9Cr steel without W after high-temperature tempering at 1023 K. With increasing W concentration, M7C3 was replaced by M23C6, and M6C formed in addition to M23C6. During subsequent aging at temperatures between 823 and 973 K after tempering, the recovery of dislocations, the agglomeration of carbides, and the growth of martensite lath subgrains occurred. Intermetallic Fe2W Laves also precipitated in the δ-ferrite grains of the 9Cr-4W steel. The effect of W on dislocation recovery and precipitation behavior is discussed in detail.

Hiroshi Araki

Papers

Single-Crystal SiC Nanowires with a Thin Carbon Coating for Stronger and Tougher Ceramic Composites

The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel

The effect of tungsten on dislocation recovery and precipitation behavior of low-activation martensitic 9Cr steels

High-frequency FTIR absorption of SiO2/Si nanowires

Fabrication in-situ SiC nanowires/SiC matrix composite by chemical vapour infiltration process