Cryogenic Heat Treatment Research Articles

Mechanical properties and surface characterisation of aluminium foam made of Al 6101 subjected to cryogenic treatment - a comparative study

Aluminium alloy foams are highly utilised material because of their high ductility, low density, high thermal conductivity, and lesser cost. Cryogenics would be an unconventional methodology amongst the material fields for the improvement of mechanical properties. The cryogenic treatment of non-ferrous alloy foams will also produce more wear resistance and longer durability products. This research is to investigate the mechanical properties and microstructural characteristics of closed-cell aluminium foam made of Al 6101 aluminium alloy with different heat regimes namely heat treatment (HT), cryogenic treatment (CT), and cryogenic heat treatment (CHT). The experimental results reveal that the cryogenic treatment of Al 6101 foam decreases the elastic limit and leads to brittleness. A comparison of the stress-strain curve emphasises that the increase of brittleness in the CHT regime is due to the reduction of the elastic region and also the scanning electron microscopic (SEM) images prove that the cryogenic treatment changes the morphology of aluminium alloy foam.

Investigation of Microstructure and Mechanical Properties of Austenite Stainless Steel 304 during Tempering and Cryogenic Heat Treatment

In the present study, the influence of heat treatment (tempering & cryogenic) on the grain orientation and few important mechanical properties of Austenite Stainless Steel 304 (ASS 304) are examined. The significant mechanical properties like ultimate strength, elongation percentage and surface hardness etc., of the experimented and untreated specimens are computed using pre standard methods and the micrographs of the specimens was conducted using metallurgical microscope. The effect of strain rate ranging from lower to higher strain rates 0.001s-1 to 0.1s-1, on true stress - true strain behaviour of tempered austenitic stainless steel 304 is investigated. Experimental results exhibited that the mechanical behaviour of ASS 304 can be reformed and improvised by several heat treatment procedures for a specific application. The results showed that the cryogenic treated specimens indicate lowest tensile strength, hardness and highest percent of elongation value compared with tempered specimen gave the maximum tensile strength, hardness and minimum percent of elongation in length value.

Effect of heat treatment and cryogenics on hardness of ductile cast iron microstructure (FCD­50)

The results of researches of possibilities of increasing the mechanical properties of pig iron with ball-bearing graphite of brand FCD-50 by the combined heat treatment are described. The scheme of multistage heat treatment, the characteristic feature of which is the operation of cooling in liquid nitrogen, is proposed. The use of such a scheme allows for increased HRC hardness characteristics. The study of the microstructure of cast iron treated with this scheme has proved the efficiency of the cryogenic heat treatment stage and determined its rational regimes.To match or approximate the properties of steel, the mechanical properties of this ductile cast iron 50 (FCD-‎‎50) must be ‎enhanced by methods such as ACTDI (austemper cryogenic and temper Ductile Iron). In this procedure, the FCD-50 specimen is inserted into the electric kitchen heater at 350 °C ‎‎(room temperature), heated to 600 °C and held at this temperature for 45 minutes. Next, the ‎specimen is heated to 900 °C and held at this temperature for 1 hour ‎‎(temperature austenisation). Then, the specimen is placed in furnace 2 at 3,000 °C for 45 minutes ‎‎(austempering process). The specimen subsequently is cooled in ‎liquid nitrogen. In this study, additional specimens were obtained for hardness and ‎microstructure tests. The as-cast test yielded a ‎hardness value of 18.39 HRC. In the hardness test for the ACTDI process, 12 ‎hours of submersion yielded the highest hardness result of 24.25 HRC. ‎In terms of the changes in microstructure after soaking changes, the amount of perlite present in the specimen was greater than that of ferrite, and the arrangement of graphite ‎nodules was better than that of the as-cast material.‎

Improvement of cutting performance of carbide cutting tools in milling of the Inconel 718 superalloy using multilayer nanocomposite hard coating and cryogenic heat treatment

In this study, milling of the Inconel 718 superalloy was performed in dry conditions with the aim of reducing the adverse effects of the coolant on the environment. As is known, cutting tools quickly complete their life due to the high-temperature on the cutting zone in the dry condition milling process of hard materials. The nanocomposite TiAlSiN/TiSiN/TiAlN thin film was deposited on the cutting tools and then subjected to cryogenic heat treatment to increase the tool life of the used cutting tools. As a result, the life of the cutting tools has been increased by the thin film coating and cryogenic heat treatment applied to the cutting tools. After cryogenic treatment at a cutting speed of 30 m/min, the tool life of uncoated, TiN-, nanocomposite TiAlSiN/TiSiN/TiAlN-, and TiAlN-coated carbide cutting tools increases by 54, 110, 29, and 30%. The applied cryogenic heat treatment resulted in an 18% increase in the hard η phase of the structure of the carbide cutting tools. In addition, cryogenic heat treatment improved the adhesion of hard coatings to the substrate. The EDS analysis applied to the worn tools revealed that the mechanisms causing wear of the cutting tools were abrasion and adhesion.

COMPARATIVE STUDY OF WEAR BEHAVIOR OF M35 TOOL STEEL ON TREATED AND UNTREATED CUTTING TOOL ON LATHE MACHINE

The aim of this study is to reveal the enhancement of wear resistance of AISI M35 tool steel by cryogenic treatment and Heat treatment by observing their tool life in terms of cutting length and surface roughness value obtained. Cryogenic treatment is often referred as cryo treatment, is an add-on process to the conventional heat treatment. In the experimentation process we have made two single point cutting which have undergone through heat treadment and cryogenic treatement. Those two tools we have fitted on standard all gear lathe machine. On Lathe machine we have conducted experimentation process for tool life keeping Speed (N), Feed (F), and Depth of Cut (D) as a input process parameters and tool life in terms of Cutting length and roughness value as a output parameter. Along with various angles and faces of tool the tool nose radios plays a very important role in producing good surface finish on component. Hence effect of this radius also has studied in this experimentation. Considering the length of paper we have not included microstructural details of material gone under processes.

Cryogenic heat treatment — a review of the current state

The deep cryogenic heat treatment is an old and effective heat treatment, performed on steels and cast irons to improve the wear resistance and hardness. This process includes cooling down to the liquid nitrogen temperature, holding the samples at that temperature and heating at the room temperature. The benefits of this process are significant on the ferrous materials, but recently some studies focused on other nonferrous materials. This study attempts to clarify the different behavior of some materials subjected to the deep cryogenic heat treatment, as well as explaining the common theories about the effect of the cryogenic heat treatment on these materials. Results showed that polymers exhibit different behavior regarding to their crystallinity, however the magnesium alloys, titanium alloys and tungsten carbide show a noticeable improvement after the deep cryogenic heat treatment due to their crystal structure.

Tribocorrosion and Electrochemical Behavior of DIN 1.4110 Martensitic Stainless Steels After Cryogenic Heat Treatment

DIN 1.4110 martensitic stainless steel is largely used in the cutlery industry due to its high corrosion resistance associated with high mechanical resistance. However, when this material works under corrosion and wear conditions at the same time, their synergistic effect can accelerate the degradation process of the alloy. Cryogenic heat treatments have been proposed to improve the dimensional stability and mechanical properties, since they minimize the amount of retained austenite. The aim of this work is to study the effect of deep cryogenic heat treatment at -80 oC and at -196 oC on the corrosion resistance and tribocorrosion behavior of DIN 1.4110 martensitic stainless steel. The microstructure, hardness, corrosion resistance and tribocorrosion behavior were evaluated. Although the heat-treated samples presented higher hardness and lower corrosion current density (icorr) compared to samples in spheroidized condition, their material removal under tribocorrosion conditions increased, which demonstrated the synergy between corrosion and wear.

Cryogenic heat treatment of the ferrous materials – a review of the current state

Deep cryogenic treatment is a supplementary heat treatment which has been used industrially since the 70s in the last century. This process includes lowering the samples temperature down to that of the liquid nitrogen (–195 ◦ C), holding the samples at that temperature for some periods of time and then warming the samples gradually up to room temperature. This process is regularly used for different kinds of steels, including the HSS, tool steels, cast iron and carburized steels. This study attempts to clarify the effect of different environmental variables on the materials, subjected to the deep cryogenic heat treatment, as well as explaining the common theories about the cryogenic behavior of the ferrous materials.

Investigating the effect of the deep cryogenic heat treatment on the corrosion behavior of the 1.2080 tool steel

Investigating the effect of the deep cryogenic heat treatment on the corrosion behavior of the 1.2080 tool steel

Effect of Carbide Distribution on Corrosion Behavior of the Deep Cryogenically Treated 1.2080 Steel

Deep cryogenic heat treatment is a supplementary process performed on steels specifically tool steels before tempering to improve the wear resistance and hardness of these materials. The carbide distribution changes via the electric current flow or the application of a magnetic field during the deep cryogenic heat treatment. Hence, the electric current and the magnetic field were applied to the samples to investigate the corrosion behavior of the deep cryogenically treated samples by electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results showed that increasing the carbide percentage and achieving a more homogenous carbide distribution during the deep cryogenic heat treatment will remarkably decrease the corrosion resistance due to a decrease in the solutionized chromium atoms in the structure as well as the increase in the martensite-carbide grain boundaries (the galvanic cell areas). Moreover, it was clarified that the electric current flow and magnetic fields reduce the carbide percentage, which leads to an increase in the corrosion resistance of these samples in comparison with the deep cryogenically treated samples.

Microstructure of Tool Steel X37CrMoV5 after Cryogenic Treatment and its Effect on Wear Resistance

<p>A deep cryogenic heat treatment (DCT) was applied to X37CrMoV5 steel, which included soaking at -160°C for 12 and 30 hours followed by tempering at 180°C. Microstructures were compared with those after conventional heat treatment (HT). Microstructures with conspicuous dendritic segregation were observed in all specimens. After HT coarser and finer tempered martensite occurred in depleted and enriched areas of carbon and alloying elements respectively. Coarse molybdenum and vanadium carbides, fine secondary Fe2MoC carbides and retained austenite were identified after HT. Deep freezing resulted in microstructure refinement, transformation of retained austenite into twinned martensite, spinodal decomposition of martensite plates and precipitation of semicoherent h-carbide. The mechanism of h-carbide precipitation was discussed. Wear rate was measured using pin-on-disc test. The best results were obtained after DCT with cryosoaking for 12 hours.</p>

Effect of Deep Cryogenic Heat Treatment on the Wear Behavior of Carburized DIN 1.7131 Grade Steel

The effects of the deep cryogenic heat treatment on the microstructural changes, wear resistance, and hardness of carburized DIN 1.7131 grade steel were investigated. Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount. In addition, after the cryogenic heat treatment, carbide shows a more uniform distribution, as compared to the conventionally treated ones. It was also clarified that the hardness of the cryogenically treated samples was improved, but the relative improvement decreases with the distance as the surface increases. It has been shown that the wear resistance improves due to the cryogenic heat treatment, and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.

Investigating the effect of holding duration at a deep cryogenic temperature on the wear behavior of DIN 1.2080 (D3) tool steel

This work focused on the effect of the holding time in a deep cryogenic heat treatment on the wear behavior, microstructural changes, retained austenite percentage and microhardness of 1.2080(D3) tool steel. These analyses were performed via optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and energy dispersion spectroscopy (EDS) to study the microstructure. A pin-on-disk wear testing machine was employed to investigate the wear behavior. The microhardness changes were measured by KOPA machine. It was shown that the deep cryogenic heat treatment eliminates retained austenite and makes a more uniform carbide distribution with higher percentages. Furthermore, some new nano-sized carbides form during the deep cryogenic treatment, thereby increasing the hardness and improving the wear behavior of the samples. It was also observed that the deep cryogenic heat treatment improves the wear behavior and microhardness of samples with an increase in the holding duration up to an optimum value: beyond that duration, the wear resistance and microhardness decreases to a specific value, and changed specifically at longer holding durations. It was also observed that the predominant wear mechanism was a combination of adhesive and tribochemical wear.

극저온 열처리된 Al7075-T6의 선삭특성 분석

Article history: In recent years, aluminum processing has been increasing in the aerospace, vehicle, airplane industries etc.,because aluminum has abundant resources and has a high specific strength. Aluminum alloys have a high coefficient of thermal expansion therefore, it is necessary to consider the temperature problem in the cutting process. The objective of this research is to investigate the machinability of a hardened aluminum alloy Al7075-T6 by using cryogenic heat treatment. The machining test is conducted by comparing the cutting force and surface roughness, corresponding to various cutting conditions of depth of cut, cutting speed, and feed rate, with those of Al7075-T0.

FE-simulation coupled with CFD analysis for prediction of residual stresses relieved by cryogenic heat treatment of Al6061 tube

This study aims to predict the residual stress relieved by cryogenic heat treatment (CHT) of an Al6061 tube. Conventional CHT commonly consists of solid-solution heat treatment, uphill quenching, and artificial ageing. To produce a new residual stress that is opposite to the original in nature, the solid-solution heat-treated aluminum parts are usually immersed in LN2 during uphill quenching with conventional CHT, followed by rapid heating of the parts using boiling water or high-velocity steam. First of all, conventional T6 and CHT experiments are conducted to measure the temperature of a tube with dimensions O200 mm × h200 mm × t10 mm. Computational fluid dynamics (CFD) analysis is conducted to calculate the convective heat transfer coefficient and temperature of the tube. These results are compared with the temperature in the experiment, and the comparison results are used to predict residual stress by means of FE-simulation. In particular, the relaxation of residual stress during artificial ageing is investigated using the Zener-Wert-Avrami function with the user subroutine. The predicted values of residual stress are compared favorably with the experimental results within a deviation of 10–15%, in contrast to measurements obtained by micro-indentation and saw-cutting tests. In addition, the experimental results show that conventional CHT can relieve as much as 57% of the residual stress induced by the water quenching of conventional T6 heat treatment.

Investigating the effect of quench environment and deep cryogenic treatment on the wear behavior of AZ91

Deep cryogenic heat treatment is a conventional supplementary treatment for steels to improve their wear resistance and hardness. Despite a variety of researches about steels, lack of investigation for the other alloys and materials is obvious. In this study, the effect of the deep cryogenic heat treatment and different quenching environments on the magnesium alloy (AZ91) was investigated via the optical microscope (OM), scanning electron microscope (SEM), hardness evaluation and wear test. For this purpose, the samples were solutionized at 420°C for 24h followed by quenching in different environments of water, air and liquid nitrogen. After that the samples were deep cryogenically treated in liquid nitrogen, followed by aging. Results show that deep cryogenic heat treatment improves the hardness and wear resistance. This behavior is a consequence of aluminum atoms jumping to the nearby defects, including dislocations. Moreover, it was clarified that increasing the cooling rate of quench environment improves the hardness after aging and that the predominant wear mechanism is abrasive.

Prediction and measurement of relieved residual stress by the cryogenic heat treatment for Al6061 alloy: mechanical properties and microstructure

The purpose of this study is to predict the residual stress resulting from the cryogenic heat treatment (CHT) which affects the mechanical properties and microstructure for Al6061 alloy. The CHT is very effective method to reduce the residual stress by quenching media such as liquid nitrogen, boiling water and steam. In this study, experimental T6 and CHT are carried out to measure the temperature of Al parts and to determine the convective heat transfer coefficient. This coefficient is used to predict the residual stress during FE-simulation. In order to consider the relaxation of residual stress during artificial ageing, the Zener-Wert-Avrami function with elasto-plastic nonlinear analysis is used in this study. The predicted residual stress is compared with the measured one by X-ray diffraction (XRD) and is found to be in good agreement with results of the FE-simulation. Further, after T6 and CHT, the electrical conductivity and hardness of the Al6061 alloy are measured to estimate the mechanical properties and its microstructure such as precipitates is observed by Transmission electron microscopy (TEM). Also, the creation of precipitates during T6 and CHT are verified by XRD with component analysis. It is found that CHT affects the residual stress, mechanical properties, and precipitation of the Al 6061 alloy.

Investigating the effect of as-quenched vacancies in the final microstructure of 1.2080 tool steel during the deep cryogenic heat treatment

In this study, the effect of the as-quenched vacancies on the formation of nano- and micron-sized carbides during the deep cryogenic heat treatment of 1.2080 tool steel was investigated. For this purpose, an electric current with the voltage of 650V and the current densities of 4.5–2A was used to clarify the effect of the vacancies as potential sites for carbon atoms jumping during the cryogenic treatment. These atoms produced some appropriate places for carbide nucleation during the tempering. This paper also showed that the common theories in the deep cryogenic heat treatment, which are based upon the dislocation mobility and formation, are not comprehensive and should be reviewed for empowerment.

Investigating the effect of ball milling during the deep cryogenic heat treatment of the 1.2080 tool steel

The effect of attrition milling on the structure and hardness of the 1.2080 tool steel during the deep cryogenic heat treatment was investigated via the scanning electron microscope (SEM), X-ray diffraction (XRD) and microhardness and hardness evaluation. Some newly formed defects were produced during the attrition milling of the samples as a result of the surface contact between the balls and samples. These defects affect the carbides nucleation during the cryogenic heat treatment. Moreover, the surface impact produces a residual compressive stress on the samples surface. These phenomena lead to an increase in the hardness and percentage of the carbides. It was also observed that milling the samples before the cryogenic heat treatment is not beneficial due to austenite aging. Furthermore, some newly nano-sized carbides were also produced during the cryogenic heat treatment in the structure, increasing the hardness further.

Effect of cryogenic deformation on the structure and properties of chromium-nickel steels

The effect of rolling at a temperature of 77 K and subsequent tempering on the structure and properties of chromium-nickel 05Kh14N14T2 and 15Kh14N14Yu1 steels is investigated. The formation of a nanocrystalline martensite phase in an austenitic matrix has been established. It is shown that additional hardening of the metal occurs due to the precipitation of intermetallic phases during heat treatment. The steels under study are high-strength and hard-magnetic after cryogenic deformation and heat treatment.