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One of the most important heat treating processes is steel carburizing. However, the relatively long process times makes carburizing (and related thermochemical processes) a particularly energy consumptive and expensive process. Thus, if significant reductions in process times or temperatures can be achieved, this would result in substantial product cost savings and reduced energy consumption. Various methods of accelerating the carburizing process have been reported previously including: the use of rare earth metals, optimization by computer control of endo gas composition, use of superficial nitriding and others. In this paper, an overview of a new process using a hydrocarbon decomposition reaction catalyst that results in substantial diffusion rate acceleration and/or the potential use of significantly lower carburization temperatures will be discussed.

The results of the stress relieving and tempering processes of steel are dependent on the process temperature and time which are correlated using Holloman-Jaffe equation or Larsen-Miller equation. These equations yield a value known as the tempering parameter, which is a measure of the thermal effect of the process. Processes that exhibit the same tempering parameter exhibit the same effect. In this paper an overview of the development of the tempering parameter, including its origin, use and limitations will be provided. In addition, recent work describing the development of more precise numerical relationships to describe the tempering process will be provided.

One of the ongoing needs in the materials industry is to facilitate significant production cost saving due to energy usage. One way to do this is to use the thermal energy generally emitted during heat treatment to facilitate additive reactions with the material surface. This has been successfully done by formulating specific lubricity additives into on a oil or aqueous quenching media. When the material is heated and subsequently quenched, the lubricity additive will then react with the surface providing substantial improvements in lubricity. This process is called: “coat forming”. The objective of this paper is to provide an overview of coat forming reactions, additives, and subsequent application performance.

Recently, a report was issued describing the use of an alternative to the commonly used thermocouple-probe assemblies for gathering time-temperature data to simulate microstructure, hardness and residual stresses of large castings of crack-sensitive steel alloys. This process involves the measurement of the increase of the water temperature in the quenching tank as a function of time as if the quench tank were a macro-calorimeter. From this data, cooling curves may be calculated which are then used to predict microstructure and hardness. However, no details of the actual modeling process used in that work have been published to date. This paper describes the results of a laboratory study which was recently performed using a round AISI 4140 steel bar to evaluate the feasibility of using water temperature rise during a quenching to generate a cooling curve for property prediction by simulation in a manner similar to that reported earlier.

Although quench factor analysis has been used by many researchers in predicting the performance of a quenchant to strengthen aluminum, it has rarely been applied to steel quenching. However, quench factor analysis posses a number of advantages over current empirical methods or more recently employed finite element thermophysical property modeling. For example, quench factor analysis can address the non-Newtonian cooling process involved with many processes utilizing vaporizable quenchants. Quench factor analysis predictions of as-quenched hardness can be successfully performed with an Excel Spreadsheet calculation. Finally, quench factors can be easily utilized in constructing databases for quenchant characterization and selection.

This paper describes the use of computational simulation to examine the heat transfer properties and resulting residual stress obtained by quenching a standard probe into various quench oils. Cooling curves (time-temperature profiles) were obtained after immersing a preheated 12.5 mm dia. × 60 mm cylindrical Inconel 600 (Wolfson) probe with a Type K thermocouple inserted into the geometric center into a mineral oil quenchant. Different quenching conditions were used, as received (“fresh”) and after oxidation. Surface temperatures at the cooling metal - liquid quenchant interface and heat transfer coefficients are calculated using HT-Mod, a recently released computational code. Using this data, the temperature distribution was calculated. The corresponding residual stresses were calculated using ABAQUS. This work illustrates potential benefits of computational simulation to examine the expected impact of different quenchants and quenching conditions on a heat treatment process.

Surface engineering encompasses numerous vital and diverse technologies in the design and wear of automotive and off-highway components. These technologies include CVD, PVD, ion implantation and conventional heat treatments such as carburizing, nitriding and carbonitriding. Although these technologies are well known, it is considerably more difficult to understand the relative importance of the various technology niches for these processes, and it is very difficult to find effective summaries of the impact of these technologies on comparative lubrication formulation and practice. The objectives of this paper are two-fold. One is to review the impact of surface engineered coatings on the surface chemistry of steel. The second objective is to review the impact of the surface chemistry obtained by different surface treatments on boundary film formation to reduce frictional losses during fluid lubrication.

Atmosphere carburizing remains one of the most important surface treatment technologies throughout the world. In this paper, various important metallurgical design variables are identified by examining the results of the carburisation of 15HN steel. These results showed the importance of the formation of martensite-retained austenite-carbide microstructure after hardening. Increasing austenization temperature causes a decrease in the carbide fraction and an increase in the fraction of retained austenite. By optimisation of the composition of these microstructures through variation of carburisation process, hardening, and tempering variables, it is possible to optimise compressive stresses, abrasive wear resistance, and contact fatigue resistance.