Trends in Heat Treatment and Surface Engineering : A Few Examples

Heat treatment has been undergoing rapid changes in recent years. Many if not all of these changes are brought about due to the stringentrestrictions being placed by environmental considerations and increasing cost of power. Surface engineering on the other hand has been assuming steadily increasing importance by virtue of developments in other technologies such as generation of intense laser beams, production and control of widely different ion beams, greater resolutions in scanning probe microscopes etc. The present article attempt to illustrate the trends in these fields through a few examples. The cases discussed are only for illustrating a few of the many trends and are in no way exhaustive

Study guide on “Technology of Structural materials and Material Science” Part 3

Study guide on have been approved at the meeting of building mechanics department (minutes No 1 from 25 August 2016) The Study guide on have been approved by the Mechanical Engineering Faculty methodological committee (minutes No 1 from 29 August 2016)“Technology of Structural materials and Material Science” is one of the basic technical disciplines in the syllabus for “Engineering mechanics” field of study. During the implementation of laboratory work considerable attention is given to the educational and experimental work for the study of materials that are used in different branches of an industry; methods of treatment and external environments The study of the theory and practice of different methods of materials strengthening is to provide a high reliability and longevity of the machine’s details, devices, tools etc. After every practical class and lab activities in the laboratory, students will fill the laboratory report. The content of the laboratory class corresponds with the syllabus of the course “Technology of Structural materials and Material Science” for students of the “Engineering mechanics” field of study. The purpose of this manual is to provide guidelines for the students in preparation for independent laboratory work and to project its results in the laboratory reports

current challenges in material choice for high performance engine crankshaft

Abstract The segment of high-performance cars will progressively deal with the trade-off among cost saving, high performances and quality due to customers' higher expectations and the regulations requests for higher-power, safer, more intelligent and environmentally-friend cars. Dealing with these complicated systems requires additional designing phases and optimization of all components in terms of performances, reliability and costs. Among such mechanical parts assembled in an Internal Combustion Engine (ICE), the crankshaft is one that still requires extra attention regarding materials choice, thermal treatments, producing processes and costs. The aim of this work is to analyze the actual and future scenarios about the material choice for the crankshaft of high-performance engines. In particular, what is considered here is the actual development and improved quality reached by base materials and manufacturing technologies for this critical component of the engine. In this context, different materials are analyzed, together with surface hardening techniques, thermal treatments and their technical and cost saving potentials

Notes and laboratory reports on “Electrical and Structural Materials” Part 2 “Structural materials”

The notes and laboratory reports have been approved at the meeting of structural mechanics department (minutes № 5 from 15 January 2018) The notes and laboratory reports have been approved by methodological committee of the faculty of engineering of machines, structures and technologies (minutes № 5 from 18 January 2018

The influence of carburising temperature on the case depth and properties of vacuum carburised precision gears

Low pressure gas carburising (LPGC) or vacuum carburising is a heat treatment process used in the aerospace and automotive industries to surface harden low alloy steel parts with carbon in the range of 0.1 to 0.25%. This project examined the LPGC process used to case harden precision gears and shafts used in various helicopter engines. Due to the stringent quality requirements specified by the OEMs (Original Engine Manufacturers) and by aerospace quality standards, approval can only be ensured through careful control of the carburising temperature, time and atmosphere during heat treatment. Final acceptance requires that the case depth, surface hardness, core hardness and component microstructure (related to the effectiveness of the quench and temper process) be controlled to within strict tolerances. This investigation utilised an industrial vacuum carburising furnace and an acetylene atmosphere to examine the effect of carburising temperature on the properties of the carburised surface layer in parts machined from 16NCD13 carburising steel. The project aimed to determine whether the total carburising time could be decreased by increasing the carburising temperature without adversely affecting the specified case depth, hardness values or microstructure. The predictions of published carbon diffusion models (taking into account the influence of temperature, changing carbon concentration and alloying element content on the diffusion coefficient of carbon in austenite) were compared with the carbon concentration profiles measured after carburising at four different combinations of time and temperature. The results showed that increasing the carburising temperature from 900°C to 940°C, while reducing the carburising time from 104 to 64 minutes, did not have any detrimental effect on the case depth, case hardness, core hardness, component microstructure or part dimensions, while resulting in a significant reduction in the total carburising time. The mechanical properties of the test pieces were within specification and the grain size was not adversely affected by the higher heat treatment temperature. Increasing the carburising temperature to 960°C (and simultaneously reducing the carburising time to 44 minutes), however, caused a reduction in mechanical properties to below specification. Published carbon diffusivity models that consider the influence of temperature, increasing carbon concentration and the alloy content of the component were found to predict the actual carbon concentration profiles to a reasonable degree of accuracy.Dissertation (MSc)--University of Pretoria, 2017.Materials Science and Metallurgical EngineeringMScUnrestricte

Kriterien für Wälzlagerstähle für das Induktionshärten

Induction hardening of bearing components offers advantages over other hardening techniques like low energy consumption and connected emissions, superior mechanical properties and the use of low alloyed steel grades. The used steel alloy for induction hardening has a pronounced impact on the hardening result. The dissertation aims at identifying a suitable and robust bearing steel for induction hardening. Based on a literature study, potential bearing steels were selected and compared in terms of heat treatment robustness using a dilatometer. Larger hardness of the prior microstructures as well as low alloyed steel grades were shown to reveal a robust hardening result. The rolling contact fatigue performance was evaluated as one important property of bearing steels. Larger carbon contents or as-heat treated hardness showed superior behavior for classical measures of rolling contact fatigue performance, while lower carbon contents led to smaller and less crack appearance. The roles of different alloying elements, prior austenite grains sizes and residual stresses were discussed. A medium carbon steel was identified as a good compromise revealing a robust heat treatment result and good fatigue performance

Indian Alloy Steels for Engineering Industries

The evolution of alloy steels during the last two decades has been characterized by serious efforts to make use of alloying elements as economically as possible and commonly to rely upon indigenous alloying elements as far as possi-ble. Nickel, cobalt, chromium , molybdenum, manganese, vanadium, tungsten, etc., are amongst the chief elements used for conveying high strength at room and elevated temperatures, toughness and corrosion resistance to alloy steels. If extensive production of alloy steels is to be undertaken in India, (a) the main alloying elements must be essentially those which occur in India and (b) the composition of alloy steels must be so adjusted that these new Indian steels will not be merely replicas of standard grades evolved in other countries, but should adequately replace them witliout impairment of properties such as hardenability and toughness together with any special characteristics called for by the service conditions. The subject has been discussed on this basis for alloy constructional steels, low-alloy high strength steels, corrosion-resistant steels, etc. The beneficial effects of rare earth and other minor additions have also been discussed. Some data in respect of alloy steels for the Indian automobile industries are presented

Notes on the course “Building Material Science” Part 1“Material Science”

“Building Material Science” for students of “Civil Engineering” consists of two parts – Part 1 “Material science” and Part 2 “ Modern building materials” and studing sn 1 semesters. Part 1 “Material science” include 16 hours of lectures, 16 hours of labs and 54 hours of individual work. Part 2 “ Modern building materials” has 18 hours of lectures, 18 hours of labs and 54 hours of individual work. “Building Material Science” is one of the basic technical disciplines in the curriculum for “Civil Engineering” field of study. The study of materials that are used in construction, alloy’s properties dependence on the chemical composition, structure, methods of treatment and external environments is of great importance for the Civil Engineering bachelors training. The study of the theory and practice of different methods of materials strengthening is to provide a high reliability and longevity of the building construction, machine’s details, devices, tools etc. Selecting the most appropriate material of construction for an application involves the making of numerous important decisions. This is true whether it be for the construction of a bridge, a household appliance, a piece of chemical processing equipment, or the decorative facing of a building. Factors such as physical and mechanical properties, corrosion resistance, workability, and cost must all be taken into consideration. With the introduction of new metallic alloys and advances in the production of the so-called exotic metals, what was the best choice several years ago may no longer be so. Over the years, improvements have been made to specific properties of various alloys. These improvements include methods to increase mechanical, physical, and corrosion resistance properties. Alternatives in composition have also been formulated to improve the workability of many alloys. In order to conduct a meaningful evaluation of a design, all the data needed to select the most appropriate material must be available. It is the purpose of this book to supply as much of this information as possible for commercially available metallic materials

The behaviour of advanced quenched and tempered steels during arc welding and thermal cutting

Quenched & tempered (Q&T) wear-resistant plate steels with martensitic microstructures have been in use for many years in the mining, defence, and construction industry due to their excellent mechanical properties (up to 1700 MPa of tensile strength and \u3e10% elongation to failure). These mechanical properties are achieved by utilisation of up to 0.4 wt.% Carbon (C), \u3c1.5 wt.% Manganese (Mn), microalloying with Molybdenum (Mo), Chromium (Cr), Nickle (Ni), Titanium (Ti), and sometimes Boron (B), and a combination of carefully designed thermomechanical processing schedule and post rolling heat treatment. In the last 10 years addition of \u3c1.5 % Ti was shown to provide superior wear resistance at a moderate C content. Improvement in the wear resistance was achieved via the formation of TiC hard particles embedded in the tempered martensite matrix. Moderation of the C content in Ti-alloyed steels allowed to obtain steels with relatively low hardness, high toughness, and enhanced weldability (due to the low carbon equivalent of the steel composition). A combination of moderate hardness and high toughness positively influenced the wear resistance. Fabrication of tools and equipment from the Q&T steels is carried out using conventional fusion arc welding and thermal cutting with oxy-fuel or plasma jet. The main problem, in this case, is the formation of an edge microstructure highly susceptible to cold cracking or hydrogen-induced cracking (HIC), which results in deterioration of mechanical properties, making steel unsuitable for the required application. In the case of Ti-alloyed steels, the heat input associated with thermal cutting and welding alters the TiC particle size distribution, in addition to the tempering of the martensitic microstructure, occurring in conventional Q&T steels. However, fabrication parameters may be controlled to avoid catastrophic microstructure deterioration and product failure. Generally, a type of welding process, environment, alloy composition, joint geometry, and size are the main causes of cracking after cutting and welding. Cracking susceptibility increases as the weld metal hydrogen content, material strength, and thickness increase. Cold cracking will occur if three conditions are satisfied: susceptible microstructure; type and magnitude of residual stresses; and importantly, the level of diffusible hydrogen that enters the weld pool. Cold cracking can be avoided through the selection of controlled heat input (depends upon current, voltage, and travel speed of welding) and preheating temperature