Hardening of a quick-speed steel tool through nitration process with nitrogen controlled potential

The study of the gas nitriding method, which allows obtaining high-quality diffuse layers in high-speed steel P6M5 on the basis of an internal nitrogen hardening zone with no brittle nitride zone, has been viewed. Research results of phase composition of nitrided steel with a change in the nitrogen potential of the atmosphere during dilution of ammonia are presented. Nitrided tool increased resistance during drilling constructional steel and titanium alloy, which is due to precipitation hardening treatment of the internal nitrogenization zone using tungsten nitrides, is given.

Mathematical models of the change in composition of the inlet atmosphere for the assumed changes in the nitrogen potential

The development of gas nitriding and the systematic expansion of its scope of application in practice means that the issue of the production of nitrided layers on steels is still in the center of interest of industry and research centers from both a cognitive and application point of view. Research mainly focuses on determining the relationship between the construction of the nitrided layer and its production parameters. The condition of full control of the nitriding process effect is the control of the nitrogen availability of the nitriding atmosphere, which depends on the value of the nitrogen potential (Np) and the degree of ammonia dissociation (α). Shaping of these parameters is carried out by controlling and regulating the composition of the inlet atmosphere. Control and regulation of the inlet atmosphere composition is important in controlling the nitrogen availability of the nitriding atmosphere and, consequently, the kinetics of nitrided layer thickness increase. The article describes models for changing the composition of the three-component and two-component inlet atmosphere. Two variants of controlling and regulating the nitrogen potential are discussed: the composition of the two-component inlet atmosphere, dissociated ammonia-ammonia and the temperature function in the heating stage of the charge.

Treatment of sidestream dewatering liquors from thermally hydrolised and anaerobically digested biosolids

A long term operation (22 months) of the sidestream treatment plant at the water and resource recovery facility at the Tilburg sewage works in The Netherlands is presented. This plant treats dewatering reject liquor from thermally hydrolysed (THP) and mesophillic anaerobically digested (MAD) biosolids. The sidestream plant is comprised of a Phospaq struvite reactor for removal and recovery of phosphate and an Anammox reactor for removal of ammoniacal nitrogen. Potential inhibiting characteristics of THP-MAD reject liquor were successfully mitigated by various measures like pre-aeration and addition of dilution water. The sidestream plant demonstrated excellent performance in handling large fluctuations in load and composition, producing effluent with stable low NH4 and BOD concentrations achieving removal efficiencies up to 90% on both NH4 and BOD.

Synthesis and electromagnetic properties of nanodendritic γ′-Fe4N

Nanodendritic [Formula: see text]-Fe4N was successfully synthesized through a nitriding process from dendritic [Formula: see text]-Fe2O3, which was prepared by hydrothermal method using potassium ferricyanide (K3[Fe(CN)6]) as iron source. The structure and electromagnetic properties of this material were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). The results revealed that the dendritic morphology can be mostly inherited from [Formula: see text]-Fe2O3 to [Formula: see text]-Fe4N by controlling the nitriding temperature, duration and nitrogen potential precisely. The dendritic [Formula: see text]-Fe4N has the saturation magnetization of 146[Formula: see text]emu/g and the coercive force of 94[Formula: see text]Oe at 300[Formula: see text]K. The maximum reflection loss is [Formula: see text][Formula: see text]dB at 3[Formula: see text]GHz with the thickness of 3.0[Formula: see text]mm for the composite sample.

Steel nitriding optimization through multi-objective and FEM analysis

Steel nitriding is a thermo-chemical process leading to surface hardening and improvement in fatigue properties. The process is strongly influenced by many different variables such as steel composition, nitrogen potential, temperature, time, and quenching media. In the present study, the influence of such parameters affecting physic-chemical and mechanical properties of nitride steels was evaluated. The aim was to streamline the process by numerical–experimental analysis allowing defining the optimal conditions for the success of the process. Input parameters–output results correlations were calculated through the employment of a multi-objective optimization software, modeFRONTIER (Esteco). The mechanical and microstructural results belonging to the nitriding process, performed with different processing conditions for various steels, are presented. The data were employed to obtain the analytical equations describing nitriding behavior as a function of nitriding parameters and steel composition. The obtained model was validated, through control designs, and optimized by taking into account physical and processing conditions. Highlights The paper shows the development of a model based on very broad experimental activity. The data were employed to provide a provisional tool for nitrided steel mechanical and microstructural behavior. A very good experimental–numerical correlation was found.

Structure and Properties of Gas Nitrided Layers on Nanoflex Stainless Steel

The paper presents results of research on nitrided layers on Sandvik NanoflexTMprecipitation hardened stainless steel. The influence of process parameters on nitriding kinetics and structure of the layers was investigated. The gas nitriding process was conducted in a mixture of ammonia 50% and products of its dissociation, as well as in 100% ammonia atmosphere at temperature range 400500°C and time between 2 and 8 h. The obtained diffusion layers were examined using the following methods: light and scanning electron microscopy, XRD phase analysis and EDS chemical analysis. Mechanical properties were tested with hardness measurements. It was found that kinetics depends on treatment temperature and nitrogen potential of the atmosphere. Moreover, treatment conditions affecting Sphase formation and expanded martensite in nitrided layers are discussed.