Modeling of as-tempered hardness in steel is essential to understanding final properties of heat-treated components. Most of the tempering mathematical models derive a tempering parameter using Hollomon-Jaffe formulation. Some recent models incorporate chemical composition into the general Hollomon-Jaffe relationship. This paper compares model predictions with a substantial set of actual tempered Jominy End Quench bars and the hardness data from them. Improvements to the models and direction for future work are discussed.

A study on the microstructural evolution of a Ni-base superalloy (Allvac 718plus) was conducted to better understand how solutionizing temperature affects the final microstructure of solutionized and aged test samples. Four different solutionizing temperatures were used to obtain different fractions of gamma prime (γ’) and delta (δ) phase precipitates. This paper describes the solutionizing treatments and presents and analyzes the results of SE-SEM, EBSD, EDS, and XRD testing.

Rapid induction hardening of martensitic steel can attain the very high strength levels needed for light-weighting components subjected to high operating stresses. Specimens of martensitic 0.6% C steels were heat treated using a dilatometer to investigate the effects of heating rates of 5 to 500 °C/s to temperatures of 850 to 1050 °C on the transformation to austenite and subsequent transformation to martensite during quenching. Selected specimens were quenched after partial transformation to austenite to assess the initial cementite precipitate size formed in ferrite during heating. Other specimens were isothermally held at the austenitizing temperature to assess cementite dissolution rates. Higher heating rates increased the Ac1 and Ac3 temperatures, and lowered the Ms temperature. Alloy content and prior microstructure also influenced the transformation temperatures.

Vacuum carburizing with high pressure gas quenching is increasingly employed to reduce near-surface intergranular oxidation and quenching distortion. It has also been shown to reduce processing times because it can be conducted at higher temperatures, up to 1100 °C. These temperatures, however, may cause austenite grain coarsening, making steel more susceptible to fatigue failure. This paper presents a study showing how microalloying carburizing steels with Mo and Nb improves resistance to austenite grain growth. The control of grain size is attributed to solute and precipitation effects.

A hypoeutectoid steel was austenitized at 840 °C for one hour and cooled at two rates. Examination by optical and scanning electron microscopy showed a change in the pearlite microstructure. Cooling in air as compared to furnace cooling reduced the pearlite interlamellar spacing and increased the hardness. The slower cooling resulted in a lower tensile strength, higher tensile elongation, and different fracture appearance.

Microstructure refinement strategies for carburized steel were evaluated to assess their effect on the fatigue performance of case carburized components. Commercial 52100 steel samples were subjected to various treatments and analyzed to determine the micro-geometry of plate martensite and the size distribution of retained-austenite regions. Decreasing reheat temperature produced finer austenite grain size, while multiple reheating cycles helped narrow grain size distribution. The refinement of austenite grain size also led to a reduction in martensite plate size and finer distribution of retained austenite.

This paper investigates the factors that influence quenching rates and temperature distributions in steel during dilatometry testing. In a prior study, the authors assessed the performance of the cooling system in a widely used dilatometer. The goal of the current work is to develop a cooling strategy that provides more uniform and possibly faster cooling in the same system. Several alternate quench concepts are analyzed, the most promising of which uses water-cooled tubes to deliver high velocity gas through a series of jets axially aligned with the test sample. The proposed cooling apparatus and its effect on the induction heating process are assessed using CFD, electromagnetic, and thermal analyses.