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Inconel 718 is widely used in chloride-bearing environments where localized corrosion resistance is critical. This study assesses the effect of continuous low-temperature plasma nitriding (425 °C, 2 h) on the microstructure, hardness, and localized corrosion behavior of Inconel 718. The nitriding treatment produced a surface layer with hardness values up to three times higher than those of the untreated material, associated with a nitrided layer of thickness 6.1–6.7 µm. X-ray diffraction confirmed the precipitation of CrN without the formation of nitrogen-expanded phases. Cyclic polarization tests revealed non-significant changes in the corrosion parameters, except for a two-fold increase in the corrosion rate of nitrided samples. Also, the critical pitting temperature (CPT) decreased by more than 30 °C on average in the nitrided condition, falling below 10 °C. These findings indicate that, although continuous plasma nitriding enhances surface hardening, it significantly compromises the alloy’s resistance to localized corrosion in chloride-rich environments.

The wear behavior of the chromium nitride (CrN) coating on piston ring material against liner material was investigated under dry conditions at room temperatures. Cat iron alloy, widely used in manufacturing of piston rings and cylinder liners, was coated by physical vapor deposition method. Wear tests were carried out on a Pin-on-Disc tribometer. Simultaneous effect of sliding velocities (0.3, 0.4, 0.6, and 0.8 m/s) and corresponding loads (10, 20, 30, and 40 N) on wear rate, friction coefficient, and temperature was analyzed. In conclusion, specific wear rate is decreasing by increase in load and velocity. The rise of temperature is 28 to 42 °C at the wear track room temperature resulting in a reduced coefficient of friction (COF) when the increase of load if from 10 to 40 N. The wear mechanism is a combination of mild to severe wear, three-body abrasion, and oxidation wear for dry conditions.

One of the most popular methods for ranking duplex stainless steels (DSSs) and predicting their corrosion properties is the calculation of the pitting resistance equivalent number (PREN). However, since DSSs are two-phase materials with a significant fraction of secondary phases and precipitates, the application of the PREN can be highly limited. This article attempted to use a new approach to describe the corrosion resistance of these steels. The corrosion resistance of two DSSs of the same class was investigated. Under identical solution heat treatments in the temperature range of 1050–1200 °C, the crevice corrosion resistance of one steel increased, while that of the other decreased. It was demonstrated that the amounts of austenite and ferrite changed similarly in these steels, and the different corrosion resistances were associated with the behaviors of secondary phases: niobium carbonitride and chromium nitride. SEM-EDS analysis was conducted to analyze the redistribution of elements between phases in both cases, showing good agreement with the thermodynamic modeling results. The PREN was calculated for each phase depending on the treatment temperature, and a method for calculating the effective PREN (PRENeff), accounting for phase balance and secondary phases, was proposed. It was shown that this indicator described corrosion properties better than the classical PREN calculated for the average steel composition. This study demonstrated how the calculation of critical temperatures (the temperature of equal amounts of ferrite and austenite, the temperature of the beginning of chromium nitride formation, and the temperature of the beginning of σ-phase formation) could describe the corrosion resistance of DSSs. Maximum possible deviations from these temperatures were defined, allowing the attainment of the required corrosion properties for the steels. Based on the conducted research, an approach for selecting new compositions of DSSs was proposed.

This study investigated the tribological and mechanical properties of chromium nitride (CrN and CrN/DLC) coatings applied to 316L steel in an artificial blood environment. The wettability of the tested surfaces was determined and the hardness was also tested using the instrumental indentation. Friction-wear tests were performed using a TRB3 tribometer in a rotating ball-on-disc configuration. The tests were performed under dry friction conditions and with lubrication using artificial blood at pH 7.45 (neutral environment) and pH 7.15 (acidified environment). Wear of the friction pairs was examined using an interferometric-confocal microscope. Artificial blood was chosen to simulate human body fluids. The use of the CrN/DLC coating reduced the coefficient of friction by 83% for dry friction, by 62% for friction with neutral artificial blood lubrication, and by 69% for friction with acidic artificial blood lubrication, respectively. Despite the increased coefficient of friction of the CrN coating, its use also contributed to reduced material wear.

Chromium nitrides such as CrN and Cr2N are often used for corrosion and wear resistant applications. In order to understand the thermodynamic stability of the nitrides, Pourbaix diagrams will be extremely useful. In this paper, Pourbaix diagrams are constructed for CrN and Cr2N using thermodynamical data for species at 298 K (25 °C) and at a concentration of 10−6 M for aqueous species. These diagrams are useful indicators for the stable regions in which these compounds can be used. The diagrams show that passive Cr2O3 films form on the surfaces where chromium nitride was present. It is argued that the formation of Cr2O3 films will degrade chromium nitride and make it much less useful as a wear resistant layer. However, the presence of nitrogen in solid solution is better for the stability of passive films.

In order to study the suitability of the S-phase layers as the interlayer for Cr2N chromium nitride coatings, a number of composite coatings were deposited by the reactive magnetron sputtering (RMS) method on austenitic steel substrates with various initial surface conditions (as delivered and polished) and their corrosion resistance was assessed. Coatings with S-phase interlayer were deposited at three different nitrogen contents in the working atmosphere (15%, 30%, and 50%), which influenced the nitrogen concentration in the S-phase. Coatings with chromium, as a traditional interlayer to improve adhesion, and uncoated austenitic stainless steel were used as reference materials. Detailed microstructural and phase composition studies of the coatings were carried out by means of scanning electron microscopy (SEM), optical microscopy (LM), and X-ray diffraction (XRD) and were discussed in the context of results of corrosion tests carried out with the use of the potentiodynamic polarization method conducted in a 3% aqueous solution of sodium chloride (NaCl). The performed tests showed that the electrochemical potential of the S-phase/Cr2N composite coatings is similar to that of Cr/Cr2N coatings. It was also observed that the increase in the nitrogen content in the S-phase interlayer causes an increase in the polarization resistance of the S-phase/Cr2N composite coating. Moreover, with a higher nitrogen content in the S-phase interlayer, the polarization resistance of the S-phase/Cr2N coating is higher than for the Cr/Cr2N reference coating. All the produced composite coatings showed better corrosion properties in relation to the uncoated austenitic stainless steel.

In this study, low-pressure gas nitriding (gas pressure of 0.01 MPa) was conducted to produce a thicker nitrided layer with high hardness and anti-corrosive properties on AISI 304 austenitic stainless steel. The effects of nitriding temperature and duration on the microstructure and surface property of nitrided layers were systematically evaluated by using optical microscope, X-ray diffraction, elemental analysis, microhardness test and potentiodynamic polarization tests. The samples were also treated under conventional gas pressure of 0.1 MPa for comparison. The results show that the low-pressure gas nitriding could restrain the precipitation of chromium nitrides effectively, which is beneficial for obtaining a thicker nitrided layer. Although the activation energy of nitrogen diffusion for low-pressure nitriding (220 kJ mol−1) is higher than that for the atmospheric pressure nitriding (196 kJ mol−1), the thickness of nitrided layers for low pressure nitriding could reach to a comparable value as that for the conventional atmospheric pressure nitriding. More importantly, the surface toughness and corrosion resistance of nitrided layers could be improved by low-pressure nitriding, which is mainly attributed to the optimized nitrogen content in nitrided layers and the reduced precipitation of chromium nitrides under low-pressure.

Aiming its analysis at the poor hardness and wear-resistance of E690 high-strength steel, and the high hardness and good wear-resistance of AlCrN-coated, combined with the laser impact micro-modeling which can store oil lubrication, this paper carries out research on the synergistic wear reduction mechanism of laser impact micro-modeling AlCrN coated on the surface of E690 high-strength steel. Multi-arc ion plating technology is used to prepare the AlCrN coating on the laser-impact micro-modeling specimen; the micro-modeling AlCrN-coated specimen is subjected to a reciprocating friction test, and the hardness and residual stress of the coated surface are measured by equipment such as a residual stress meter and a microhardness tester. The microstructure and physical elements of the surface wear before and after the preparation of the coating are analyzed by scanning electron microscope (SEM), confocal three-dimensional morphometer and XRD diffractometer, respectively. The results show that the prepared AlCrN-coated materials were well-bonded to the substrate. Compared with the micro-molding-only specimens, the average friction coefficient and wear amount of the micro-molded AlCrN-coated specimens with different micro-molding densities and depths decreased compared with the micro-molded specimens; among them, the average friction coefficient of the specimens with a micro-molding density of 19.6% and a depth of 7.82 µm was 0.0936, which was the lowest. Additionally, the AlCrN coating enhances the stability of the friction process of the specimen and reduces the amount of wear of the specimen. Under the premise of ensuring the anti-wear and stability properties of the material, the best integrated friction performance was achieved at a micro-molding density of 19.6% and a depth of 24.72 µm. A synergistic wear reduction and lubrication model of micro-molding and AlCrN-coating was established.

Ceramic materials are usually hard but brittle, and it is challenging to achieve a simultaneous enhancement of strength and plasticity using conventional strengthening methods. In ceramic materials with similar atomic size and properties, the fabrication of nanotwins is a promising approach to enhance the plasticity, but it is unknown whether the strategy works for transition metal nitrides. Herein, nanotwinned CrN (NT-CrN) with a twin density of 9.0 × 10 15  m -2 and twin-containing grain volume fraction of about 52 % is prepared by adjusting the ion kinetic energy during growth. Owing to the twin boundaries, NT-CrN exhibits high hardness (>36 GPa) and enhanced room-temperature plasticity at the same time. Compression deformation of over 40% without brittle failure is achieved. The enhanced room-temperature plasticity is attributed to the distributions of nanotwin boundaries (nano-TB) which allow special slipping by twisting the polyhedron constructed by nano-TB without bond breakage. The accompanying twin proliferation and fusion subsequently dissipate the energy to enhance the plasticity. Nanotwinned ceramic chromium nitride (NT-CrN) is prepared by precisely controlling the deposition ion energy, which demonstrates high hardness (>36 GPa) with room-temperature compressive plasticity exceeding 40% without brittle fracture.

Chromium Nitride (CrN) coatings have widespread utilization across numerous industrial applications, primarily attributed to their excellent properties. Among the different methods for CrN coating synthesis, direct current magnetron sputtering (DCMS) has been the dominant technique applied. Nonetheless, with the expanded applications of CrN coatings, the need for enhanced mechanical performance is concurrently escalating. High-power impulse magnetron sputtering (HiPIMS), an innovative coating deposition approach developed over the past three decades, is gaining recognition for its capability of yielding coatings with superior mechanical attributes, thereby drawing significant research interest. Considering that the mechanical performance of a coating is fundamentally governed by its microstructural properties, a comprehensive review of CrN coatings fabricated through both techniques is presented. This review of recent literature aims to embark on an insightful comparison between DCMS and HiPIMS, followed by an examination of the microstructure of CrN coatings fabricated via both techniques. Furthermore, the exploration of the underlying factors contributing to the disparities in mechanical properties observed in CrN coatings is revealed. An assessment of the advantages and potential shortcomings of HiPIMS is discussed, offering insight into CrN coating fabrication.