High-Efficient Gas Nitridation of AISI 316L Austenitic Stainless Steel by a Novel Critical Temperature Nitriding Process

Abstract

To improve the surface properties of austenitic stainless steels, a thick S-phase layer was prepared by using a novel critical temperature nitriding (CTN) process. The properties of the thick S-phase layer were optimized by controlling the process parameters. The microstructures and phase compositions of CTN-treated layers were characterized by the optical microscope, scanning electron microscope and X-ray diffraction, respectively. The surface properties, including corrosion and wear resistance, were systematically investigated by the electrochemical workstation, micro-hardness tester and ball-on-disk tribometer, respectively. The results showed that a thick S-phase layer with a thickness of 18 to 25 μm can be fabricated in a short time by critical temperature nitriding, which represented higher efficiency than conventional low-temperature nitriding. Although the most top surfaces of CTN-treated layers contain massive iron nitrides, there are no precipitates in the inner nitrided layer. The electronic work function calculated by first-principles method has confirmed that those iron nitrides had a slight influence on the corrosion resistance of nitrided layers. The optimized CTN-treated layer exhibited a comparable corrosion resistance and wear resistance as the low-temperature nitrided layer. The CTN process is considered a potentially highly efficient surface modification method for austenitic stainless steels.

In-Depth Understanding of the Chemical Stripping Mechanism of AlSiY Coatings on Nickel Superalloys by First-Principles Calculation

“…The chemical stripping process can be considered as a redox reaction that occurs on the surface of the AlSiY coating. The higher the EWF is, the harder it is to oxidize [20]. Additionally, there exists galvanic corrosion between surfaces with different EWFs.…”

Surface Characteristics of Vacuum-Plasma-Sprayed Reinforced Stainless Steel Coatings with TiC Particles

“…Research on iron-based thermally sprayed coatings has shown promising results in various applications. Consequently, several stainless steel alloys have shown good corrosion properties, especially when they were exposed to cavitation erosion conditions [7][8][9][10]. De et al [11] in their research demonstrated that 304 stainless steel stands out as an outstanding material resistant to cavitation, offering significant application potential across various fields.…”

“…This is attributed to its favorable characteristics, including good plasticity, high corrosion resistance and cost effectiveness. Also, the martensitic steels [3,9,10] have demonstrated outstanding resistance to cavitation erosion, and this performance was closely associated with their hardness. Nevertheless, in numerous instances, softer austenitic or dual-phase steels have proven to be even more advantageous, primarily because of their superior strain hardening properties [3,[12][13][14][15][16].…”

Comparison of Nitriding Behavior for Austenitic Stainless Steel 316Ti and Super Austenitic Stainless Steel 904L

“…Thus, the nitriding of austenitic stainless steel with the aim of increasing its tribological properties has been developed [1][2][3]. Here, nitrogen insertion in the temperature range between 300 and 450 • C leads to a super-saturated phase with nitrogen still in solid solution [4][5][6][7][8][9]. This so-called expanded austenite is a metastable phase which can accommodate nitrogen up to 38 at.%, resulting in anisotropic lattice expansion up to 12% [10].…”