Papers by Keyword: Nitrided Layer

Abstract: A computer program in Python was developed based on the mathematical model, which allows obtaining preliminary calculations of the diffusion coefficient and nitriding time of a punch part. As a result of a numerical experiment, the process of nitrogen diffusion into the depth of the part was studied. The redistribution of nitrogen occurs as a result of diffusion due to the nitrogen concentration gradient in the volume of the part and the high quenching temperature. The numerical experiment confirms the full-scale experiment. Nitrogen penetration into the depth of the metal occurs precisely at the quenching temperature. The nitrogen content in the internal nitriding zone due to the nitrogen released from the surface layer increases and decreases on the surface with the exposure time of the part. Computer modeling and research of the diffusion coefficient in the process of heat treatment after ion nitriding made it possible to establish that for tool steels, diffusion along grain boundaries occurs. Thus, the use of complex ion nitriding (CIN), i.e. ion nitriding and subsequent heat treatment of nitrided parts allows you to change the phase composition and increase the depth of the nitrided layer due to nitrogen doping, control the nitrogen concentration and hardness along the depth of the nitrided layer due to selected modes.

Abstract: The plasma nitriding as a technology for finishing of material surface layers was carried out on selected material. The effect of plasma nitriding conditions on the thickness and hardness of nitrided layer was investigated. The influence of plasma nitriding period on the thickness of the plasma nitrided layers was comprehensively assessed on the C55 steels. Plasma nitriding was carried out on selected material at 500 °C under 280 Pa with a mixture atmosphere of H₂ and N₂ in the plasma nitriding equipment. The period of the plasma nitriding process was changeable from 5 to 20 hours. Measurements of the properties of nitrided layers of selected material were solved by using experimental methods in accordance with standards. The samples were characterized by GDOES spectrometry, optical microscopy, and hardness testing. The depths of the plasma nitriding layers were also detected using cross-sectional microhardness profiles. Relation between plasma nitriding period and a thickness of a nitrided layer was explained and has shown that microhardness and surface hardness of mentioned samples were significantly increased.

Abstract: Household refrigeration represents 17.3% of home energy consumption in the USA and 47% in Brazil. This article overviews a multidisciplinary approach to develop a traditional hermetic compressor (oil lubricated, with several rotating parts), into an oil-less, linear motion, innovative compressor, with improved efficiency, versatility and sustainability. This involves the development of surface engineering processes combining purpose-oriented phases applied to soft substrates to achieve high wear resistance and load support and low friction coefficient. Initially, the role of the environment (air, CO₂ and R600a) on the tribological behaviour of a commercially available Si-rich multifunctional DLC coating deposited on AISI 1020 steel is illustrated. In sequence, the influence of the thickness of different layers (DLC and CrN) on sliding wear is analysed. Results are presented using an original approach (3D triboscopic maps) for two distinct configurations (increasing load and constant load) and findings are confronted with numerical simulations using Film Doctor^®. Finally, a low cost process to obtain a multifunctional coating (different nitrided layers + DLC) is described, which uses a unique thermal cycle reactor capable of coating parts in industrial scale with reduced cost.

Abstract: Purpose of this paper is presentation of forms of hydrogen degradation in steel along with pointing out methods for hydrogen degradation prevention. The paper outlines influence of nitrided layer on 34CrAlNi7-10 steel to its susceptibility to hydrogen degradation. Investigation was carried out with the use of slow strain tensile rate test (SSRT). Fracture surfaces after SSRT test were examined with scanning electron microscope (SEM) to reveal a mode and mechanism of cracking.

Abstract: Technology of plasma nitriding is widely used to increase the surface hardness, fatigue strength, wear and corrosion resistance of steels [1, 2]. In this study, the properties of plasma nitrided steel of various diameters at various pressures are investigated. There was obtained new information about possibilities of plasma nitriding technology and its applications to the cavities with diameters of 6, 8 and 10 mm and a penetration depth of 400 mm.

Abstract: This paper presents investigation of surface layers. The diffusion layers were produced by using different parameters of reactive atmosphere (N2:H2). The research of the surface layers was performed using scanning electron microscope (SEM). The results of energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) analysis are presented. Research reveals the influence of chemical constitution of reactive atmosphere on the change of properties of nitrided layers.

Abstract: The nitrided layer on the surface of LZ50 (0.50% C) carbon steel was prepared by ion nitriding technique and its characterizations were detected by using Vickers hardness tester, profilometer, scanning electric microscope (SEM), optical microscope (OM) and X-ray diffraction (XRD). Rotational fretting is one of basic running modes in contact configuration of ball-on-flat, to which was paid little attention. The rotational fretting wear behaviors of the nitrided layer and its substrate steel were comparatively studied in dry condition under varied angular displacement amplitudes (θ) in range of 0.125º-1º, imposed normal load (Fn) of 20 N and a constant rotational speed of 0.2º/s. The experimental results showed that the nitrided layer presented rough and porous surface and high hardness was mainly consist of ε-Fe2-3N and γ׳-Fe4N phases. Compared with the substrate steel, the nitrided layer had a significant effect on reducing the friction coefficient and improving the fretting wear resistance, though the nitrided layer almost didn’t change the fretting running regimes of the substrate steel. In the partial slip regime, lower friction coefficients and slight damage appeared for the nitrided layer due to the coordination of elastic deformation of contact zones. In the slip regime, the friction coefficient of the nitrided layer was lower than that of the substrate in the initial stage as a result of the preventing plastic deformation by its high hardness surface. The rotational fretting wear mechanism of the nitrided layer in the slip regime was mainly identified as abrasive wear, oxidative wear and delamination. As a result, the nitrided layer presented a better capability for alleviating rotational fretting wear.

Abstract: The nitrided layer formed on Type 304 steel after gas nitriding was studied using TEM and so on. (1) Dependency of the nitriding temperature and time on the depth of the nitrided layer was studied. The following equation was obtained. L2=8.7*108*EXP(-146,000/RT)*t (2) Nitrided layer formed at both 570°C for 3 hrs and 410°C for 48 hrs had high density of dislocation, stacking fault and lattice strain. (3) Nitrided layer formed at 570°C was mainly composed of є-Fe3N, and had much Fe4N and CrN. (4) On the other hand, the nitrided layer formed at 410°C was mainly composed of S-phase, є-Fe3N was not detected and Fe4N and CrN were very little. N content in the nitrided layer formed at 410°C was about 7-8 mass%. (5) Nitrided layer formed at 410°C showed good corrosion resistance.