Field Of Heat Treatment Research Articles

New insights into the optimisation of the solution heat treatment process and properties of CMSX-4 superalloys

For nickel-based single-crystal superalloys, simultaneously reducing the segregation and optimising the microstructure is a primary challenge in the field of heat treatment. To further improve rupture life, the element partition, microstructure evolution, and creep behaviour of the second-generation nickel-based single-crystal superalloy CMSX-4 under five different solution processes were studied using electron microprobe, scanning electron microscopy, and transmission electron microscopy. Under the same conditions, both continuous heating and remelting heat treatment exhibited higher elements homogenisation efficiency. Moreover, it was found that the improvement of element segregation can make γ′ phase smaller and more uniform. These heat treatments reduced the incipient melting tendency or eliminated the incipient melting eutectic, thereby increasing the peak heat treatment temperature of the CMSX-4 alloy. However, remelting heat treatment results in a significant increase in the porosity of the alloy, leading to a deterioration in performance. Finally, based on the above study, a novel process combining stepwise heating and continuous heating was proposed, which not only increased the peak solid-solution temperature but also prevented the incipient melting and optimized the microstructure. After using the novel process, the durability of the alloy increased by 48 % from 240 to 356 h under the test conditions of 980 °C/250 MPa. The higher proportion of the γ′ phase, narrower matrix channel, and denser dislocation network were the main reasons for the improvement in the rupture life.

Features for formation of copper-zinc coatings

The results of X-ray diffraction and microspectral analysis of a copper-zinc coating applied by gas-dynamic spraying using a mechanical mixture of copper, zinc and corundum particles with subsequent heat treatment in a furnace in the temperature range of 420...430 °C and a holding time of up to 180 minutes are presented. It is shown that during the deposition process, copper diffuses into zinc and a gradient structure based on copper, zinc and an electron-type solid solution based on Cu5Zn8 (γ-phase) is formed, the mass fraction of which is 31, 16 and 47 %, respectively. Based on the analysis of the results of microspectral analysis, the diffusion coefficient in copper to zinc is calculated, which is equal to DCu = 0.72•10–12 m2 /s. It was found that after exposure in the furnace for 180 min, the phase composition of the copper-zinc coating (α-phase and β′-phase) corresponds to brass grade CW508L. Based on the analysis of the change in the grating period of copper, depending on the exposure time, it is shown that the heat treatment field with an exposure time in the furnace of 60 min coating can be considered brass.

Studying of the dielectric loss factor of grain by indirect method

Significant losses of grain crops at various stages of cultivation, harvesting, post-harvest processing and storage dictate the need to technologies and equipment for these processes. Currently, one of the most promising directions in the field of heat treatment of grain is the use of combined influence methods with the use of electrophysical effects. The purpose of this work is to develop and test a method for measuring the dielectric loss factor by an indirect method, which makes it possible to control the humidity of grain material exposed to microwave. The paper presents the equipment and the design of the experimental installation. The results of the experiment were subjected to regression analysis. The results of experimental studies and dependencies can be used for modelling microwave effects on agricultural bulk materials in electromagnetic modelling software, such as CST Studio.

Advanced Heat Treatment Equipment Technology And Product Development of Metal Materials

From the current analysis of steel materials in the field of heat treatment and offline heat treatment, the implementation of advanced heat treatment equipment and processes for automated metal materials in China has carried out numerous innovations. In order to improve the technical level of localized equipment and promote the continuous development of new industrialization processes, the use of green manufacturing processes to achieve heat treatment of steel and non-ferrous metals is the focus of current research. This paper focuses on the analysis of advanced heat treatment equipment, process and product development of metal materials, and proposes to adopt green manufacturing concept and carry out research and development on advanced heat treatment equipment and technology of metal materials. It is expected to have reference value for improving rolling technology and continuous rolling automation in China.

ADVANCED TECHNOLOGIES FOR HOIST UNITS SERVICE LIFE INCREASING

The operating experience of hoist units for underground and overhaul of wells in the fields of the Bashneft oil campaign and their technical maintenance at the departments of technological transport have shown that, upon expiration of their service life, they are written off as scrap metal. For the reliability of sufficient residual safety margin and maintainability of hoisting units by the end of service life, certain manufacturers examined each unit separately by type of work when performing scheduled preventive maintenance schedules for the period from 2013 to 2018 in a specialized workshop of the oil company Bashneft. Analysis of the repair of individual parts and assemblies during the implementation of the schedule of preventive repair shows that the hoisting units for the most part have a large margin of safety. It can be confirmed the reliability of the large residual margin of safety and maintainability of the masts of the hoisting units that have worked out their factory life. The advanced technologies in the field of heat treatment and spraying with carbide powders of the mating working surfaces of the parts (in the design of the winch braking mechanism) of the hoisting unit have been changed. Particular attention is paid to mast construction elements that are subject to cyclic loads, corrosive effects (the mast post area at the wellhead) and even shock loads. Based on the results of an in-depth analysis of wear and its causes, using non-destructive testing technologies for parts and assemblies, appropriate technologies for restoration of unit parts are selected, such as chemical-thermal heat treatment (nitriding) in electric shaft furnaces, gas-thermal spraying with hard-alloy wear-resistant powders.

Metallographic Examinations Performed on Automotive Parts Through Several Case Studies

Abstract Metallurgical analysis is widely used in the field of heat treatment of metals to ensure the quality of the treatments carried out on a wide variety of industrial parts and treatments carried out. It is therefore a valuable tool for subcontractors of the heat treatment industry to monitor their production and treatment response on various parts. Through different examples, we will present actual cases that involve in particular automotive parts. We show that there is a strong interdependence between material and heat treatment, one being related to each other, a successful treatment depends both on the metallurgical quality of the material and the production quality of the heat treatment process. We will discuss the type of treatments like: vacuum hardening or under protective atmosphere, surface induction hardening, carburizing, nitriding and brazing.

Electron meets nitrogen: combination of electron beam hardening and nitriding

AbstractCombined heat treatments, also known as duplex or hybrid technologies, offer new structure/property relationships in layered matrix compounds. The treatment sequence is critical. There are within reach both properties and property gradients that are impossible to achieve using the respective single treatment processes alone nor by simple addition of the effects of the single processes. Good technical progress is given by the combination of thermochemical treatment with high energy beam surface hardening, in particular electron beam hardening. After a historical survey (milestones) of the combination of thermochemical with thermal (surface) heat treatment technologies, the paper deals with the principles of the combining electron beam hardening after nitriding and vice versa , electron beam hardening before nitriding and the effects on microstructure and properties. Typical examples of industrial application are discussed. In this field of heat treatment, further development is focused on combinati...

Influence of Transformation Plasticity on Residual Stresses and Distortions due to the Heat Treatment of Steels with Different Carbon Content

The field of heat treatment of steels offers a large variety of applications for the use of simulation tools. It always includes the development of residual stresses and distortions. The geometry of the part, the composition of the material, the heat treatment process as well as the initial state of the part interact with each other in complex ways and have an influence on the distortion of the part. Using simulation the temporal development of temperature, phases, stresses and distortions while quenching as well as the residual stress distribution and distortion after quenching can be calculated. Transformation plasticity has been proved to be very important for heat treatment simulation. Three steels with identical contents of alloying elements but different carbon contents of 0.2, 0.5 and 0.8 wt. % were analysed. The influence of transformation plasticity during the martensitic transformation on the distortions and residual stresses after quenching of cylinders made out of the three steels was analyzed in simulations and compared to experimental results.

Mathematical treatment of non-isothermal transformations

Prediction of transformation kinetics in steel at varying temperature is of great practical importance in different areas of heat treatment and material science. By formal generalization of the conventional isothermal kinetic functions applied for characterizing thermally activated processes, new types of kinetic function were generated which are suitable for the phenomenological description of non-isothermal processes. On the basis of these generalized kinetic functions, various numerical quantities allowing the concise characterization of the processes taking place at varying temperature may be derived. These quantities involve equivalent time and temperature and extended variants of well known complex time–temperature parameters (e.g. Hollomon–Jaffe parameter). With the help of these quantities, non-isothermal processes may be compared using numerical criteria. Application of the method suggested in the field of heat treatment is demonstrated by two examples. One is related to the prediction of hardness decrease due to tempering in a hardened steel, while the other concerns the development of a new type of tempering chart which can be applied generally for determining the required tempering parameters.MST/496