Effect Of Nitriding Time Research Articles

Effect of nitriding conditions and operation temperatures on dry sliding wear properties of the aluminum extrusion die steel in the industry

Hot work tool steels are widely preferred in the hot extrusion of aluminum alloys. Nitriding of die steels in the aluminum extrusion industry is a well-accepted surface hardening method against surface wear and deformation. In this study, substrate material (DIN 1.2344 steel) is diffusion coated by salt bath nitriding method for 1 h, 2 h, and 3 h. The effect of different nitriding conditions on hardness, tensile and impact properties, wear behavior, and coefficient of friction is studied. Diffusion hardened surface is examined with different characterization techniques. The effect of nitriding time on diffusion layer thickness, tensile properties, impact energy, and wear resistance properties are investigated. It is shown that increasing nitriding time enables thicker diffusion layers that modify the adhesive's wear mechanism to abrasive. Increased nitride layer thickness resisted friction much more compared to less nitrided specimens. On the contrary of wear resistance, tensile properties are reduced due to the diffusion layer’s notch effect.

Design, preparation and characterization of iron nitride magnetic abrasives

In order to effectively polish the surface of the titanium alloy workpiece, a novel type of iron nitride magnetic abrasives was designed, prepared and characterized. Theoretically, first-principles were used to analyze the effects of phase compositions of iron nitrogen compounds on the mechanical and magnetic properties of the abrasive, and ε-Fe3N and γ′-Fe4N were determined as the grinding phase compositions with the simultaneously improved properties of hardness, ductility and magnetism. In the experiments, the core-shell structured iron nitrogen compounds were prepared by nitriding the iron powders of about 250 μm with ammonia at 600 °C, and the effects of nitriding time, ammonia pressure and cooling method on the product were investigated. The composition, morphology, magnetic properties and mechanical properties of the product were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), magnetometer and nanoindenter, respectively. Under experimental conditions of ammonia pressure of 0.2 Mpa, nitriding time of 3 h and water quenching, the abrasive was obtained with the external grinding phase of ε-Fe3N and γ′-Fe4N in a thickness of 35.10 μm and the internal ferromagnetic phase of α-Fe. Its magnetic saturation intensity and hardness were 148.5 A m2 kg−1 and 8.15 GPa, respectively. Grinding with this abrasive, the surface roughness of Ti–6Al–4V alloy plate was effectively reduced from 0.305 μm to 0.077 μm.

Effect of Nitriding Time on the Structural Evolution and Properties of Austenitic Stainless Steel Nitrided Using High Power Pulsed DC Glow Discharge Ar/N2 Plasma

A high power pulsed DC glow discharge plasma (HPPGDP) system was employed to perform fast nitriding of AISI 316 austenitic stainless steel in Ar and N2 atmosphere. In-situ optical emission spectroscopy and Infrared pyrometer measurements were used during the plasma nitriding to investigate the effect of dynamic plasma on the nitriding behaviour. SEM and EDX, XRD, Knoop indentation, and tribo-tests were used to characterise microstructures and properties of the nitrided austenitic stainless steel samples. HPPGDP produced high ionization of both Ar and N2 in the plasma that corresponded to dense ion bombardment on the biased steel samples to induce effective plasma surface heating and to form high nitrogen concentration on the biased steel surfaces, and therefore fast nitriding (> 10µm/hour) was achieved. Various phases were identified on the nitrided stainless steel samples formed from a predominantly a single phase of nitrogen supersaturated austenite to a multi-phase structure comprising chromium nitride, iron nitride and ferrite dependent on the nitriding time. All the nitrided AISI 316 austenitic stainless steel samples were evaluated with high hardness (up to 17.3 GPa) and exceptional sliding wear resistance against hardened steel balls and tungsten carbide balls.

Synthesis of porous Si3N4/SiC ceramics with rapid nitridation of silicon

Porous Si3N4/SiC ceramics were prepared with Si and SiC as raw materials, Y2O3 as sintering additive and ZrO2 as nitrided catalyst through a rapid nitration process. The nitriding rate as a function of temperature and duration was investigated. The porous Si3N4/SiC ceramics with 8wt% monoclinic ZrO2 addition that was nitrided at 1400°C for 2h exhibited the highest nitridation degree of 95%. The experimental results also demonstrated that the reciprocal formation of ZrO2 and ZrN can effectively enhance the level of nitridation by suppressing the melting of silicon in micro-regions. The effects of nitriding time on the mechanical properties of the specimens with ZrO2 as a catalyst was also studied. After nitrided at 1400°C for various durations from 2 to 8h, the porous Si3N4/SiC ceramics with the properties of a porosity over 39.8%, a flexural strength over 88.9MPa and a linear shrinkage lower than 0.6% were achieved. The systematic investigation reveals the catalytic mechanism of ZrO2 in the synthesis of Si3N4/SiC ceramics.

Solar gas nitriding of Ti6Al4V alloy

The main purpose of this work was to study the activating effect of concentrated solar energy (CSE) on the high-temperature nitriding of Ti6Al4V alloy. Solar nitriding was conducted using a low-cost solar installation based on a Fresnel lens with a maximum density power of 250W/cm2 at its focus. Prior to the solar nitriding study, Ti6Al4V was submitted to high-temperature thermochemical treatments using an electrical furnace in a conventional manner. A comparison between the two processes considering the effect of nitriding time and temperature on the hardness, thickness and composition of the nitrided layer is presented. Characterisation of the treated samples by optical and SEM microscopy, microhardness measurements and XRD analysis reveals an important reduction in the nitriding time when concentrated solar energy is used versus the traditional method. The maximum hardness of the solar nitrided samples (2100HV) was achieved after treatment at 1200°C for 15min. This value is similar to that obtained when samples were heated at the same temperature in the electrical furnace for 8h.

Effect of volumetric alloying in a compressed nitrogen atmosphere on its solubility and alloy steel hardness

Thermodynamic aspects are considered for alloying steels in a molecular nitrogen atmosphere under pressure. Examples of standard steels 25Kh5M and 18Kh2N4MA are used to present nitriding kinetics: the effect of nitriding time, nitrogen pressure, and temperature on nitrided layer thickness. The effect of subsequent heat treatment on nitrided layer microhardness is studied.

Effect of nitriding time on secondary recrystallization behaviors and magnetic properties of grain-oriented electrical steel

The effect on secondary recrystallization behaviors and magnetic properties of grain-oriented electrical steel of nitriding time from 0 to 240 s in the acquired-inhibitor method has been studied. It was found that the volume fraction of nitride precipitates increased with increasing nitriding time. However, the average diameter of the nitride precipitates decreased with increasing nitriding time. Two kinds of nitride precipitates were found to have formed after primary recrystallization annealing. A fine rod-shaped precipitate was found to be Si 3N 4 and and a coarse, lozenge-shaped precipitate was MnSiN 2. Moreover, primary grain size decreased with increasing nitriding time due to retarding of the grain growth by precipitates. After secondary recrystallization annealing, the specimen that was nitrided for 30 s obtained the largest volume fraction of abnormal growth grains and largest area percentage of Goss grains. Conversely, specimens that were nitrided more or less than 30 s demonstrated poor secondary recrystallization and obtained low area percentage of Goss grains. Furthermore, the optimum nitriding time to obtain the best magnetic properties was 30 s. In addition, the optimum nitrogen content was 150 ppm.

Effect of nitriding time on the nitrided layer of AISI 304 austenitic stainless steel

The effect of plasma nitriding time on the microstructure and phase composition of nitrided layers on AISI 304 stainless steel was investigated. The phase composition and structure of the nitrided layer have been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis of samples treated at 420 °C showed the presence of γ N phase in the nitrided layers for all nitriding times involved in this study. The lattice parameters calculated based on γ N(111) and γ N(200) were different and became larger with time for up to 5 h of nitriding treatment. The surface hardness of nitrided layer was also increased with nitriding time. The maximum thickness of the nitrided layer reached 27 μm after 44 h of treatment in this study.

Surface modification and characterisation of Ti–Al–V alloys

Ti–10V–3Al–2Fe and Ti–6Al–4V alloys used in aircraft industries were nitrided using a conventional d.c. plasma technique. The effect of nitriding time, temperature and atmosphere were investigated in detail. X-ray diffraction analysis confirm the formation of TiN and Ti 2N phases on the nitrided specimens. Load-dependent microhardness measurements combined with microsturctural analysis revealed the unique features of the case-hardened materials. The microhardness after the nitriding treatment was found to be 17.64 GPa (50 g). From the case of depth profile and microstructure (optical microscopy) the thickness of the nitrided layer was estimated to be 20–50 μm. The corrosion rate of the alloys investigated using potentiostatic polarisation method in sulphide environment was found to be lower than in chloride environment.