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Introduction: Psoriasis is one of the most common dermatological diseases. It is characterized by a chronic course with periods of exacerbations and remissions. The recurrent nature of the disease and the influence of environmental factors on its course require the patients not only to be treated but also to have knowledge of prophylaxis and proper skin care. Aim: Obtaining information on the level of knowledge of patients suffering from psoriasis in the field of triggering factors and proper skin care. Material and methods: A total of 130 patients with psoriasis participated in the study. The research tool was the author's questionnaire addressed to patients. Results: Research has shown that the main source of knowledge for people with psoriasis was the Internet (85%). Only 17% obtained information about the disease from medical personnel. The respondents were aware of the negative impact of only some environmental factors, such as: injuries (63%), stimulants (77%), stress (95%), and infections (69%). Most subjects attributed the therapeutic effect to brine baths (74%). Usually the patients were aware of the oiling (85%) and moisturizing (33%) effects of emollients on psoriatic lesions. Only 46% of the respondents obtained a positive test result. Demographic variables correlated with the level of knowledge. Conclusions: The knowledge of psoriasis patients about exacerbating factors and proper skin care is insufficient. [ABSTRACT FROM AUTHOR]

The surface microstructure and growth behavior of an Fe0.4 mass%C alloy formed by lithium-added salt-bath nitrocarburizing were investigated. The Fe0.4 mass%C alloy was prepared by arc melting and nitrocarburized by a salt-bath containing Li+, Na+, K+, CNO-, and CN- at 823K from 0.1 h up to 10 h. A compound layer forms on the surface at the beginning of nitrocarburizing, and then an oxide layer forms on the compound layer after nitrocarburizing for 1.0 h. Afterwards, the thickness of both layers increase. A grain boundary oxide forms at the interfaces of columnar crystals in the compound layer. The oxide consists of LixFe1-xO with an NaCl-type structure, and the growth of the oxide layer is controlled by the outward diffusion of iron in the oxide layer. Meanwhile, the compound layer consists mainly of an ε-Fe2(N,C)1-y phase and a slight £A-Fe4(N,C)1+z phase near the substrate. [ABSTRACT FROM AUTHOR]

In the present study, DIN 31CrMoV9 (1.8519) steel samples were initially treated by salt bath- (SNC), gas- (GNC) and plasma-nitrocarburising (PNC) and afterwards oxidised for increased corrosion protection. The thickness and hardness of the oxide and compound layer as well as the diffusion zone were measured. Surface topographies and microstructures were analysed with optical microscopy, laser scanning microscopy and scanning electron microscopy (SEM), while the detailed chemical compositions of the sample surfaces were determined with energy-dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Tribological tests for characterisation of wear and frictional behaviours of the treated samples were performed under unlubricated sliding conditions. Results show that, although different nitrocarburising processes yield very similar hardness profiles and compound layer thicknesses, their surface morphology and oxide layer properties can be significantly different. On SNC samples, the thickest oxide layers were formed, which had a different chemical composition than those formed on GNC and PNC samples. Furthermore, SNC samples provided the highest wear resistance and only on these samples, the oxide layers were not removed during tribological testing. It is thus possible that a correlation between the oxide properties and the favourable tribological behaviour of the SNC samples exists. [ABSTRACT FROM AUTHOR]

Experimental and industrial data are obtained about the heating rate and degree of Cr reduction for a vertical section of the workspace of an ore reduction electric furnace during treatment of a mixture of lean and rich chromium ores in relation to melting period. A scheme of proposed for the temperature fields and degree of chromium reduction in reaction zones of an ore reduction furnace using data about physicochemical characteristics of the ore raw material, determined under laboratory conditions. It is shown that the degree of Cr reduction in the lower levels of the furnace bath before tapping reaches 95%, and at the end of tapping it reaches up to 85%. [ABSTRACT FROM AUTHOR]

Low-temperature salt bath nitriding of heat treated and tempered 13/4 Martensitic stainless steel (13/4HTT) was carried at 450 °C (N450) and 500 °C (N500) for 10 h each. The nitrided samples were characterized by using x-ray diffractometer, field emission scanning electron microscope and optical microscope. The nanohardness and elastic modulus of the cross section of nitrided specimen were measured by nanoindentation test using Hysitron TI950 triboindenter. The nitrided 13/4HTT (N450 and N500) and 13/4HTT specimens were subjected to slurry erosion test in a slurry pot tester. The test was conducted for 48 h, and weight loss was measured after every 6 h. The relative speed of slurry with respect to specimen was 4.55 m/s. It was found that the weight loss due to erosion of the N450 is 83% less than that of 13/4HTT and that of N500 was 92% more than that of 13/4HTT. The erosion mechanism is correlated to the phases present in the specimens. The improvement in the slurry erosion resistance of N450 is due to presence of expanded martensite (αN-Fe). Increasing the temperature of nitriding to 500 °C led to the decrease in the slurry erosion resistance of N500 due to the formation of brittle CrN phase. [ABSTRACT FROM AUTHOR]

Bored barrels are one of the primary parts of small arms. In order to enhance the service life of bored barrels, specimens of 1Cr12Ni2WMoVNb (GX-8) steel bored barrels were treated by QPQ salt bath at temperatures 530 °C for 1–4 h, followed by the same post-oxidation process with heating temperature of 440 °C for 1 h. QPQ nitrided layers were formed on the surface of GX-8 steel after QPQ salt bath and the optimized treatment time was determined to be 1 h. Specimens with and without QPQ-1 h were studied by micro-hardness test, SEM, wear resistance test, Tafel polarization curves, salt spray corrosion and ball firing. Layers formed during QPQ-1 h contains a mixture of magnetite (Fe 3 O 4 ), Fe 1-X O, CrN, ε phase, γ′-Fe 4 N and α-Fe phases. This layer leads to significant improvement in wear resistance as a result of remained Fe 3 O 4 film, while the fine distribution of nitride precipitates introduces high hardness and large residual microstresses. The formation of thick Fe 3 O 4 film results in an improvement in the corrosion resistance of steel. After the breakdown of Fe 3 O 4 film, the absence of chromium in solid solute by precipitation of chromium nitrides and carbides leads to significant decreases in corrosion resistant. The QPQ-1 h process results almost one times increases in the lifetime of bored barrels, as a result of wear resistance improvement after QPQ treatment. [ABSTRACT FROM AUTHOR]

Nanometal-glass hybrid nanocomposites are formed by the ion exchange technique of dipping the host matrix glass in the molten salt bath. This study aims to investigate Ag-ion exchanged and annealed soda-lime silicate glasses in terms of their optical and structural properties. The effects of experimental conditions (composition of the salt bath, temperature and time of ion exchange and annealing process, the atmosphere of annealing) on the plasmonic and optical behavior were examined. The produced nanometal-glass hybrid nanocomposites were characterized by UV-Vis-NIR, HRTEM-EDS, SEM, XRD, and AFM to determine nanoparticle size, shape, structure, silver particle growth, and glass surface topography. [ABSTRACT FROM AUTHOR]

In this research, the effect of rapid tempering on the microstructure, mechanical properties and corrosion resistance of AISI 420 martensitic stainless steel has been investigated. At first, all test specimens were austenitized at 1050 °C for 1 h and tempered at 200 °C for 1 h. Then, the samples were rapidly reheated by a salt bath furnace in a temperature range from 300 to 1050 °C for 2 min and cooled in air. The tensile tests, impact, hardness and electrochemical corrosion were carried out on the reheated samples. Scanning electron microscopy was used to study the microstructure and fracture surface. To investigate carbides, transmission electron microscopy and also scanning electron microscopy were used. X-ray diffraction was used for determination of the retained austenite. The results showed that the minimum properties such as the tensile strength, impact energy, hardness and corrosion resistance were obtained at reheating temperature of 700 °C. Semi-continuous carbides in the grain boundaries were seen in this temperature. Secondary hardening phenomenon was occurred at reheating temperature of 500 °C. [ABSTRACT FROM AUTHOR]

Wear resistance, corrosion properties and structure of reinforced layers deposited on steel AISI 321 with carbonitriding by the quench-polish-quench (QPQ) Tennifer® process with subsequent oxidation are studied. The structure of the layers is investigated by scanning electron microscopy with energy dispersive local analysis and x-ray diffractometry. Steel wear resistance is determined by a pin-on disk test, and oxide layer adhesion is determined by a scratch method. Pitting corrosion resistance is determined by plotting cyclic polarization curves. [ABSTRACT FROM AUTHOR]

In this article, the technology of salt bath carburizing at low temperature (640 °C) is used to prepare the titanium carbide thin film on Ti6Al4V alloy surface. The processed alloy sample surface phase and elements are observed by XRD and EDAX. The hardness of sample surface and permeability layer are measured by the MH-3 type microhardness meter. And the friction and wear contrast tests of the uncarburized and carburized samples are carried out using the M2000 friction and wear testing machine. The results show that: high hard phase carbide Ti8C5 is generated on the sample surface. The processed sample surface hardness is 953.28HV, which is 2.57 times of the original; The friction and wear properties of the carburized sample improve significantly; At 100 N, the uncarburzed wearing loss is 29 times of the carburized wearing loss, and at 300 N, the friction coefficient is reduced by 55.9 %. [ABSTRACT FROM AUTHOR]

Carbon steel AISI 1045 (0.45% C) is studied as a model material for rapid nitriding in a salt bath at 660°C (instead of the conventional 560°C). The methods of optical microscopy, x-ray diffraction and measurement of microhardness and corrosion resistance are used to study the microstructure and the phase composition of the nitrided layer. It is shown that salt bath nitriding shortens the process considerably and raises its efficiency; the microhardness and the corrosion resistance grow and the nitride layer acquires a γ′-Fe4N phase. [ABSTRACT FROM AUTHOR]

AA7075 Al alloy sheet shows low r-value (plastic strain ratio) and low deep drawability. To increase average r-value ( -value) of AA7075 Al alloy sheets, the sheets were asymmetrically rolled and subsequently heat treated in a salt bath as the first action, followed by the second asymmetry rolling and subsequent heat treatment in a salt bath. The second 22% asymmetrically rolled and subsequent heat-treated AA7075 Al sheet shows 1·41 times higher average r-value (-value) than that of initial specimen. This result could be explained by the texture changes of AA7075 Al alloy sheet after two steps asymmetry rolling and subsequent heat treatment. [ABSTRACT FROM AUTHOR]

Direct electro-deoxidation of metal oxides has become quite popular in the production of metals and alloys. In this process, metal oxide cathode is directly reduced to a metal in a molten CaCl2 salt bath. The anode material used is graphite. Over the years, graphite is reported to cause numerous process difficulties. Recently, based on the solid oxide membrane technology, yttria-stabilized zirconia (YSZ) has been tested as oxygen ion conducting membrane for the anode. The success of using a membrane implies its long-term stability in the bath. In this paper, it is seen that YSZ chemically degrades in a static melt of CaCl2 or CaCl2-CaO. The degradation occurs by leaching of yttria into solution leading to the formation of monoclinic zirconia which, being porous, reacts with the molten electrolyte to form calcium zirconate. However, on application of voltage, YSZ degrades via a different mechanism. The metallic calcium produced during electrolysis increases the electronic conductivity of the salt, apparently leading to the electrochemical reduction of zirconia to ZrO2-x. As a result, localized pores are formed which allow the infiltration of salts. Addition of yttria to the salt is seen to prevent both the chemical and electrochemical degradation of the membrane. [ABSTRACT FROM AUTHOR]

The influence of an applied current on the recovery and recrystallization of pure Cu has been investigated. By comparing samples heated by the Joule effect with those heated in a salt bath, it is shown than recovery and recrystallization are greatly accelerated by the current. At low temperatures, where only recovery occurs during conventional thermal treatments, fully recrystallized microstructures are obtained when the heating is applied through the Joule effect. [ABSTRACT FROM AUTHOR]

A novel rapid salt bath nitrocarburizing technology was primarily developed by additionally applying direct current (D. C.) electric field on the basis of traditional technique (NM). The results showed that D. C. electric field could significantly enhance the nitrocarburizing efficiency, shorten the holding time and decrease the treating temperature comparing with the NM. To get a composite layer thickness of 18 μm at treating temperature of 575 °C, the holding time was shortened from 100 min in NM to less than a half by additionally applying 7.5 V D.C., and the thickness was increased from 18.0 μm up to 29 μm at the same holding duration of 100 min. And it was found that the enhancement effect was closely related to the voltage of D. C. electric field, voltage higher than 3 V was necessary to get obvious enhancement effect. The main enhancement mechanism was analysized as well. [ABSTRACT FROM AUTHOR]

This paper deals with the physico-chemical and mechanical properties of soda lime silicate float glass treated in KNO3 baths with different purity levels. The potassium concentration profile in the surface layers was measured by EDXS and correlated with the residual stress frozen in the material, which was determined by a procedure based on the measurement of the strengthened sample curvature deriving from progressively etching one of its surfaces. This allowed pointing out a significant influence of the used salt. In order to better understand the phenomena and mechanisms underlying the surface equilibrium conditions, micro-Raman measurements were also performed on the glass surface in the aim to investigate the variation of the glass microstructure after ion-exchange in the different salt baths. [ABSTRACT FROM AUTHOR]

The paper discusses the reasons behind current trends for substituting cast iron castings by aluminum alloys. In particular it is shown that it is possible to produce thin wall castings (control arms, cantilevers and rotors) made of ductile iron without the development of chills, cold laps or misruns, and with a strength to weight ratio of up 87 MPa cm3/g. In addition, austenitizing at 900 °C for 20 minutes and then austempering in a salt bath at 350 °C for 15 minutes promotes the development of a fully ausferritic matrix in thin wall castings with a the strength to weight ratio increase of up to 154 MPa cm3/g. Finally, it is shown that thin wall castings made of ductile or austemperded cast iron can be lighter and with superior mechanical properties then their substitutes made of aluminum alloy. [ABSTRACT FROM AUTHOR]

Nitrocarburizing of the type SAE 2205 duplex stainless steel was conducted at 450 °C, using a type of salt bath chemical surface treatment, and the microstructure and properties of the nitrided surface were systematically researched. Experimental results revealed that a modified layer transformed on the surface of samples with the thickness ranging from 3 to 28 μm changed with the treatment time. After 2205 duplex stainless steel was subjected to salt bath nitriding at 450 °C for time less than 8 h, the preexisting ferrite zone in the surface transformed into austenite by active nitrogen diffusion. The main phase of the nitrided layer was the expanded austenite. When the treatment time was extended to 16 h, the preexisting ferrite zone in the expanded austenite was decomposed and transformed partially into ε-nitride precipitate. When the treatment time extended to 40 h, the preexisting ferrite zone in the expanded austenite was transformed into ε-nitride and CrN precipitate. Further, a large amount of nitride precipitated from preexisting austenite zone. The nitrided layer depth thickness changed intensively with the increasing nitriding time. The growth of the nitride layer takes place mainly by nitrogen diffusion according to the expected parabolic rate law. The salt bath nitriding can effectively improve the surface hardness. The maximum values measured from the treated surface are observed to be approximately 1400 HV after 8 h, which is about 3.5 times as hard as the untreated material (396 HV). Low-temperature nitriding can improve the erosion/corrosion resistance. After nitriding for 4 h, the sample has the best corrosion resistance. [ABSTRACT FROM AUTHOR]

This article presents the salient features of a new process for the recovery of metal values from secondary sources and waste materials such as slag and flue dusts. It is also feasible in extracting metals such as nickel and cobalt from ores that normally are difficult to enrich and process metallurgically. The salt extraction process is based on extraction of the metals from the raw materials by a molten salt bath consisting of NaCl, LiCl, and KCl corresponding to the eutectic composition with AlCl as the chlorinating agent. The process is operated in the temperature range 973 K (700°C) to 1173 K (900°C). The process was shown to be successful in extracting Cr and Fe from electric arc furnace (EAF) slag. Electrolytic copper could be produced from copper concentrate based on chalcopyrite in a single step. Conducting the process in oxygen-free atmosphere, sulfur could be captured in the elemental form. The method proved to be successful in extracting lead from spent cathode ray tubes. In order to prevent the loss of AlCl in the vapor form and also chlorine gas emission at the cathode during the electrolysis, liquid aluminum was used. The process was shown to be successful in extracting Nd and Dy from magnetic scrap. The method is a highly promising process route for the recovery of strategic metals. It also has the added advantage of being environmentally friendly. [ABSTRACT FROM AUTHOR]

Nitriding is usually used to improve the surface properties of steel materials. In this way, the wear resistance of steels is improved. We conducted a series of studies in order to investigate the microstructural, mechanical and tribological properties of salt bath nitrided AISI 4140 steel. The present study has two parts. For the first phase, the tribological behavior of the AISI 4140 steel which was nitrided in sulfinuz salt bath (SBN) was compared to the behavior of the same steel which was untreated. After surface characterization using metallography, microhardness and sliding wear tests were performed on a block-on-cylinder machine in which carbonized AISI 52100 steel discs were used as the counter face. For the examined AISI 4140 steel samples with and without surface treatment, the evolution of both the friction coefficient and of the wear behavior were determined under various loads, at different sliding velocities and a total sliding distance of 1000 m. The test results showed that wear resistance increased with the nitriding process, friction coefficient decreased due to the sulfur in salt bath and friction coefficient depended systematically on surface hardness. For the second part of this study, four artificial neural network (ANN) models were designed to predict the weight loss and friction coefficient of the nitrided and unnitrided AISI 4140 steel. Load, velocity and sliding distance were used as input. Back-propagation algorithm was chosen for training the ANN. Statistical measurements of R2, MAE and RMSE were employed to evaluate the success of the systems. The results showed that all the systems produced successful results. [ABSTRACT FROM AUTHOR]

The effects of salt-bath nitriding time on the microstructure, microhardness, and erosion-corrosion behavior of nitrided 17-4PH stainless steel at 703 K (430 °C) were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and erosion-corrosion testing. The experimental results revealed that the microstructure and phase constituents of the nitrided surface alloy are highly process condition dependent. When 17-4PH stainless steel was subjected to complex salt-bathing nitriding, the main phase of the nitrided layer was expanded martensite ( α`), expanded austenite (S), CrN, FeN, and FeN. The thickness of nitrided layers increased with the treating time. The salt-bath nitriding improves effectively the surface hardness. The maximum values measured from the treated surface are observed to be 1100 HV for 40 hours approximately, which is about 3.5 times as hard as the untreated material (309 HV). Low-temperature nitriding can improve the erosion-corrosion resistance against two-phase flow. The sample nitrided for 4 hours has the best corrosion resistance. [ABSTRACT FROM AUTHOR]

The article focuses on the changes in the manufacturing technologies and technical trends regarding the demand for high-pressure large-scale aluminum plate-fin heat exchangers in cryogenic industry. It considers corrugated fins' provision as enlarged heat transfer surfaces in the liquid channels as the major characteristics of a plate-fin heat exchanger, resulting to greater area of heat transfer. It adds the introduction of salt bath furnace by Sumitomo Precision Products.

Abstract: The process of tempering a martensitic medium carbon steel was investigated with the aim to study resulting material properties. The experimental results were used to model residual stresses caused by local heating, with the finite element method. Tempering was followed for times from 0.1s up to 1h by using laser heating and conventional salt bath furnace treatments within the temperature interval 500–700°C. In addition, the thermal expansion was evaluated using dilatometry. Experiments showed that the initial stages of martensite decomposition, associated with loss of crystal tetragonality, proceed almost instantly. An initial large decrease of hardness within the first tenth of a second of the tempering process was measured, followed by only limited further softening with increased tempering time. Thus for the current material the tempering time had limited influence on hardness, governed primarily by the peak temperature during the heating process. Finite element modelling of rapid local heating and cooling showed that the tempering behaviour and associated dilatation effects yield a peak temperature dependent residual stress field with a broad tensile stress distribution for the case of un-tempered martensite. However, for tempered martensite the residual stress field depends primarily on the heating rate and peak temperature and shows large gradients with tensile stresses in the surface and compressive below. Thereby, for both cases, residual stresses were obtained but with completely different residual stress gradients. [Copyright &y& Elsevier]

Abstract: Influence of nitriding time on the microstructure and microhardness of AISI 321 austenite stainless steel was investigated, using a complex salt bath heat-treatment at low temperature, 430°C. Experimental results revealed that after salt bath nitriding, a modified layer was formed on the surface of substrate with the thickness ranging from 2μm to 30μm with changing treating time. The nitrided layer depth thickened extensively with increasing nitriding time. The growth of the nitrided layer takes place mainly by nitrogen diffusion according to the expected parabolic rate law. Scanning electron microscopy and X-ray diffraction showed that in 321 stainless steel subjected to complex salt bathing nitrided at such temperature for less than 8hours, the main phase of the nitrided layer was expanded austenite (S phase) by large. When the treatment time is prolonged up to 8hours and more, S phase is formed and subsequently transforms partially into CrN, and then the secondary CrN phase precipitated. With treating time prolonged, more CrN precipitates formed along the grain boundaries in the outer part. In the inside part between the some CrN and the substrate, there is still a broad single S phase layer. All treatments can effectively improve the surface hardness. [Copyright &y& Elsevier]

Abstract: In this study the medium carbon steel was nitrocarburized in gas and salt bath, forming three layers (oxide layer, compound layer and diffusion layer) on the surface of the specimen. The very high cycle fatigue (VHCF) tests were carried out and the results show that fatigue limits of the specimens treated in gas and salt bath are improved by 120% and 100%, respectively, compared to that of the untreated specimens. For the specimens treated in gas, from which the oxide layer was removed or both the oxide layer and compound layer were removed, the S–N curve of the former shows a step-wise shape while the latter continuously decreases and both of them show no fatigue limit in VHCF regime. However, all the specimens treated in salt bath have the same fatigue strength and show the fatigue limit in VHCF regime whether both the oxide layer and compound layer are removed or only the former is removed. [Copyright &y& Elsevier]

Abstract: Two different grades of steel, DC 04 (non alloyed steel) and 15 CrMoV 6 (alloyed steel) were studied; both of them were salt bath nitrided with QPQ process. They were subjected to different durations of nitriding sequences, 2h, 3h and 8h while the duration for the last sequence, i.e. oxidation remained the same. Microhardness measurements showed that the alloying elements had a strong influence on the profile and on the surface hardness value. For each grade, the maximum surface hardness value was already obtained after a 2h treatment. The surface constitution was observed by XRD; the presence of Fe3O4was noticed above the compound layers made up of ε and γ′ nitrides. Cross sectional observations by SEM revealed that the growth kinetics of compound layers follows a parabolic law. The layers'' thickness and constitution have also been confirmed by EDS analysis. On increasing nitriding duration, γ′ nitride content decreases while ε nitride content increases. For longer nitriding durations, mostly ε nitride and Fe3O4 are observed on the surface of both grades. It seems that for long nitriding sequences, additional elements are not essential for compound layers'' nature. [Copyright &y& Elsevier]

Abstract: The electrolytic reduction process of actinide oxides in a LiCl salt bath at 923K has been developed for nuclear fuel reprocessing. Since some salt-soluble fission products, such as Cs, Sr and Ba, accumulate in the LiCl salt bath, their effect on UO2 reduction was investigated. In the experiments, UO2 specimens were reduced by potential- or current-controlled electrolysis in various LiCl salt baths containing up to 30mol% of KCl, CsCl, SrCl2 or BaCl2. The rate of UO2 reduction in a LiCl salt bath was considerably decreased by the addition of alkali metal chlorides (KCl and CsCl) and slightly decreased by BaCl2 addition. SrCl2 addition had no appreciable effect. It was suggested that the diffusion of O2− ions from the inside of UO2 specimens to the bulk salt determined the reduction rate during the electrolysis and that the effect of salt composition was related to the solubility of O2− ions in the salt bath. [Copyright &y& Elsevier]

The effect of quenching in molten alkaline salt bath medium on the microstructure and surface properties of AISI 1045 steel in comparison with oil was investigated. Salt bath medium used in this research contained 40% NaOH and 60% KOH with addition of 5 wt.% water at 205 °C. Hardening of 1045 steel in this medium resulted in an almost uniform microstructure, which consisted of fine martensite and bainite. In comparison, the microstructure of oil quenched sample was martensite, ferrite, widmanestatten ferrite, and pearlite. Quenching in salt bath lead to improved surface properties, i.e., decrease in surface roughness and a good bearing area curve. [ABSTRACT FROM AUTHOR]

In the present work, the transformation characteristics of ductile iron austempered from intercritical austenitization temperature ranges were investigated. For this purpose, an unalloyed ductile cast iron containing 3.50 wt% C, 2.63 wt% Si and 0.318 wt% Mn were intercritically austenitized (partially austenitized) at various temperatures and then rapidly transformed to a salt bath held at the 365 °C for austempering for various times to produce dual matrix structure with different ausferrite volume fractions in ferrite matrix. A microstructure map was created to illustrate the transformation of products quantitatively as a function of austempering time for a particular intercritical and austempering heat treatment temperature and time. It was demonstrated that the total volume fraction of transformed phases was approximately constant for all austempering times after rapidly transforming samples from a particular intercritical temperature to austempering temperature. It was found out that the new ferrite (It is also called epitaxial ferrite) introduced into the intercritically austenitized structure during austempering and its content was dependent on the intercritical austenitizing temperature and austempering time. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Quench–Polish–Quench complex salt bath heat-treatment (QPQ) on surface microstructure of the 17-4PH stainless steel (SS) was investigated. A bright zone (compound ɛ-Fe2(N,C)) is formed at the outermost surface of the nitrocarburized sample, followed by a zone (mixture Fe3N/Fe4N/CrN/α-Fe) which is slightly etched. A thin oxides zone (Fe3O4/FeO) is formed at the outer surface of the post-oxidized sample, followed by a zone (mixture Cr2N/ɛ-Fe2(N,C) and the inner zone (CrN/αN). A significantly high amount of oxygen is found at the outermost surface of the post-oxidized sample. The push-effect of oxygen leads to the peak nitrogen concentration, while the peak carbon concentration at the front of the nitrided layer is due to the push-effect of nitrogen. High microhardness values (>1200 HV0.1) is obtained at the surface and then drops abruptly at the case/core interface to substrate microhardness value for both of the nitrocarburized and post-oxidized samples. [Copyright &y& Elsevier]

Salt bath oxinitriding is a duplex surface treatment developed to improve tribological and corrosion properties of ferrous materials. In this research, gray cast iron samples were nitrided at the temperature range of 480°C–580°C, and then oxidized in an oxidative salt bath. The phase composition of surface layer was identified by X-ray diffraction. Using a microhardness tester, hardness of nitrided gray cast iron was measured. Corrosion behavior of treated (nitrided and oxinitrided) samples was evaluated using potentiodynamic polarization technique in 3.5% NaCl solution. XRD analyses indicate that the surface layer in nitrided and oxinitrided samples is composed of ε-iron nitride (Fe2-3N) and magnetite (Fe3O4), respectively. Results show that the corrosion resistance of gray cast iron can be improved up to 170%. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure of nitro-carburized and post-oxidized 304L austenitic stainless steel (SS) produced by a Quench–Polish–Quench complex salt bath process (QPQ) was investigated. The nitro-carburized coating as a whole consists of CrN, γ′-Fe4N and expanded austenite S(γN). On the post-oxidized surfaces, XRD analyses revealed the existence of a superficial compound ξ-Fe2(N,C) sub-layer, the presence of magnetite (Fe3O4) and a small amount of FeO. At greater depth from the surface of the post-oxidized surface, S(γN) is formed and subsequently transforms partially into CrN and ferrite/martensite (αN). A modestly higher sub-surface hardness and a superior hardness profile were obtained by post-oxidizing, although its surface hardness was lower than that produced by nitro-carburizing alone. [Copyright &y& Elsevier]

Abstract: Systematic materials characterization of the Quench-Polish-Quench complex salt bath heat-treatment process (QPQ) surface modified 316L steel was investigated. The results reveal that the nitro-carburized sample surfaces consist of Cr2N/γ´-Fe4N and CrN/γ-Fe, while the post-oxidized sample surfaces are comprised of CrO3, (Fe3O4)/ε-Fe2(N,C), γ′-Fe4N and S(γN)/CrN/α-Fe. Nuclei ε-Fe2N1− x accumulates at the interface between oxide layer and nitride compound layer by the help of post-oxidation. The diffraction peak lines of S-phase (γN) move gradually towards higher diffraction angles as increasing depth of 15 μm to 35 μm. An increased content of oxygen is recorded in the post-oxidized surface layer down to the depth of approximately 15 μm, a small peak concentration of carbon occurs at the front of the nitrided layer. Micro-hardness of the post-oxidized samples reaches about 1300 HV0.1 near the surface region and then reduces sharply across the case/substrate interface. [Copyright &y& Elsevier]

The quenching capacity of hot salt baths is studied and compared with that of oil baths. The microstructure and mechanical properties of steel AISI 1045 (the Russian counterpart is steel 45) are determined after different variants of quenching, namely, in a salt bath (40% NaOH and 60% KOH) without water and with 5 wt.% water at various temperatures and in oil at room temperature. [ABSTRACT FROM AUTHOR]

Nitriding technology has gone a long way, from the old gas nitriding to the relatively recently developed plasma nitriding. The latter has replaced the process of “soft nitriding” in the automotive industry based on nitrocarburizing in cyanide salt baths. It seemed that the high toxicity of the initially used compositions for soft nitriding (Tufftride or Tenifer) should have eliminated salt baths from the industry. However, they are still rather widely used. The replacement of old compositions by nontoxic ones has solved fundamental problems of environment protection. Low-temperature nitriding technology also advanced considerably. Salt bath nitriding is a very active process, more intense than that of gas nitriding and nitrocarburizing including the processes of plasma nitriding. The reactivity of the nitriding medium and the final efficiency of the process with allowance for the cost of the equipment have to be taken into account. An additional advantage of salt bath nitriding is the possibility of treatment of stainless maraging steels. The present work is devoted to comparison of the processes of treatment in a nontoxic salt bath and in a gas medium and discussion of the advantages of nitriding in nontoxic salt baths. [ABSTRACT FROM AUTHOR]

A method of coating diamond and graphite with polyalloys, such as Ti–Co–Cu, Cr–Ni–Cu, W–Cu–Co, etc., is presented in this paper. By adding a small amount of Ti powder, CoCl2 and CuCl into NaCl–KCl molten salt system, and immersing diamond or graphite into it, the reactions which listed thereafter: Ti+CoCl2→TiCl2+Co, Ti+CuCl→TiCl2+Cu, C+TiCl2→TiCl4+TiC, etc., occurred, and finally a Ti–Co–Cu coating was deposited on the diamond or graphite surface. Other polyalloy coatings, such as Cr–Ni–Cu, Cr–Co–Cu, and W–Cu–Co, etc., were also deposited in almost the same way. The coated materials were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with a wavelength dispersive spectrometer (WDS) line profile analysis. XRD analysis showed that the carbides of Ti, Cr, or W were formed during the coating process. It was also found that no vacuum or protective atmosphere was needed during the process. [Copyright &y& Elsevier]

A new effect which allows direct formation of thin metal films of controlled morphology is described. Patterns of glass-ceramic opal are developed in photosensitive glass samples by UV irradiation and heat treatment. The samples are then ion exchanged in molten salt baths containing Ag+ or Cu+ ions. On subsequent firing in a hydrogen atmosphere, continuous films with typical thin metal films properties grow on the opal regions of the samples. Discontinuous films, characterized by activated resistivities and switching, grow on the glassy regions. [ABSTRACT FROM AUTHOR]