Effect of aging on the corrosion resistance of 2101 lean duplex stainless steel

The precipitation behavior of Cr2N during isothermal aging in the temperature range from 700 °C to 950 °C in Fe-18Cr-12Mn-0.48N (in mass percent) high nitrogen austenitic stainless steel, including morphology and content of precipitate, was investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The isothermal precipitation kinetics curve of Cr2N and the corresponding precipitation activation energy were obtained. The results show that Cr2N phase precipitates in a cellular way and its morphology is transformed from initial granular precipitates to lamellar ones in the cell with increasing aging time. The nose temperature of Cr2N precipitation is about 800 °C, with a corresponding incubation period of 30 min, and the ceiling temperature of Cr2N precipitation is 950 °C. The diffusion activation energy of Cr2N precipitation is 296 kJ/mol.

Precipitation Kinetics of Cr2N in High Nitrogen Austenitic Stainless Steel

The demand for energy is growing day by day owing to population growth worldwide. There is thus a need to search alternate source of energy that is easily available and environmentally benign. Therefore, to meet the challenges and decrease the dependency on fossil fuel, researchers are focusing on alternative resources that are easy to handle, economic, environment-friendly, confined, and vast. Therefore, recent advances on metal nitrides for photocatalysts in energy storage, hydrogen production, sustainable organic conductor, and environmental purification are timely and are discussed in this chapter. The different types of metal nitrides such as covalent nitrides, ionic nitrides, boron nitrides, interstitial nitrides, metal nitrides, and sulfur nitrides are discussed, along with their preparation, fabrication, and application. Graphitic carbon nitride (g-C3N4) and transition metal nitride (TMN)-based photocatalysts have also been discussed.

Metal Nitrides and Graphitic Carbon Nitrides as Novel Photocatalysts for Hydrogen Production and Environmental Remediation

Effects of Mo on the Precipitation Behaviors in High-Nitrogen Austenitic Stainless Steels

The aging precipitation behavior in Mn18Cr18N austenitic stainless steel was investigated at temperatures from 600 °C to 900 °C. During isothermal aging treatment, the primary precipitate was Cr2N with a = 0.478 nm and c = 0.444 nm, and it preferentially nucleates along initial grain boundaries and gradually grows towards the interior of grains in discontinuous cellular way. Meanwhile, a small amount of granular face-centred cubic M23C6 with a = 1.066 nm also were observed, which mainly form along grain boundaries. The effect of these precipitates on mechanical properties of the alloy was studied. It was found that precipitates result in degeneration of the matrix hardness. Meanwhile, the SEM morphologies of aged tensile sample show that the brittle fracture predominates during deformation, i.e. the fracture mode transforms from intergranular fracture to transgranular fracture with the increasing of aging time. Compared with the solution-treated sample, the strength of the aged tensile samples slightly decreases and plasticity remarkably deteriorates.

Aging precipitation behavior and its influence on mechanical properties of Mn18Cr18N austenitic stainless steel

The precipitation behavior of M 2 N and the microstructural evolution in a Cr-Mn austenitic stainless steel with a high nitrogen content of 0.43mass% during isothermal aging has been investigated using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The aging treatments have led to the decomposition of nitrogen supersaturated austenitic matrix through discontinuous cellular precipitation. The precipitated cells comprise alternate lamellae of M 2 N precipitate and austenitic matrix. This kind of precipitate morphology is similar to that of pearlite. However, owing to the non-eutectoidic mechanism of the reaction, the growth characteristic of the cellular precipitates is different from that of pearlite in Fe-C binary alloys. M 2 N precipitate in the cell possesses a hexagonal crystal structure with the parameters a = 0.4752nnm and c = 0.4429nm, and the orientation relationship between the M 2 N precipitates and austenite determined from the SADP is [0110] M2N //[101]γ, [2110] M2N //[010]γ,

W.F. Cui

Papers

Precipitation behavior of M2N in a high-nitrogen austenitic stainless steel during isothermal aging