A patented DANTE Controlled Gas Quench (DCGQ) process was developed for high precision distortion control during quench hardening. The DCGQ process follows a recipe of quenching time and the ambient gas temperature designed by computer modeling, with a specified maximum allowed temperature difference in the part section during the martensitic transformation.

In this study, we developed the heat treatment simulation that can consider the difference in phase transformation behavior and strength characteristics in response to heterogeneous composition by calculating the TTT diagram and stress-strain curve corresponding to the composition at each position of the simulation model.

This study derived the mechanism by which previous processing processes affect heat treatment quality, especially “variation in deformation,” and clarified a method for predicting it using heat treatment simulations. We investigated the metal structure and residual stress at the completion of machining for a round bar and performed a heat treatment deformation simulation with this in mind and were able to reproduce the heat treatment deformation.

This study investigates the effect of vapor blanket duration in quenching oil on the mechanical properties and distortion of JIS-S45C carbon steel and JIS-SCM435 low-alloy steel. Four types of heat treatment oils with varying vapor blanket stage lengths were tested on key-grooved cylindrical specimens. Results indicate that quenching oils with longer vapor blanket durations produced smaller distortions, while oils with shorter durations caused larger distortions.

This study investigates the interaction between tempering processes and the formation of tempering transformation induced plasticity (T-TRIP) in 50CrMo4 steel during laser heat treatment. Various configurations, including single and double laser treatments, were examined along with different initial material states and heat treatment parameters.

The localized heat input during laser powder bed fusion (PBF-LB) additive manufacturing creates unique thermal histories resulting in distinctive residual stress distributions and microstructures that affect fatigue performance. This study examines the relationship between geometrical features and residual stresses in 316L stainless steel components with topology-optimized geometries such as Y-struts and various node shapes.

This study focuses on evaluating the transferability of an established induction heat treatment simulation model to the sintered steel Fe-1.8%Cr-0.6%C (Astaloy CrA). As the porosity affects the electromagnetic, thermal and metallurgical material behavior during induction hardening, these material properties were experimentally determined as a function of temperature across all relevant phases.

This study examines the impact of thermal post processing, specifically induction hardening and tempering, on the fatigue performance of laser powder bed fusion (PBF-LB) manufactured AISI 4140 steel. Results highlight the importance of porosity control, with induction hardening effectively addressing near-surface porosity issues in non-machined parts.

To develop a behavior model, properties such as Young's modulus, viscous stress, kinematic hardening, isotropic hardening, yield strength and transformation-induced plasticity parameter (TRIP) for austenite and martensite were determined using a specially developed experimental set-up.

This work serves to expand upon the fundamental idea of high convection quenching (HCQ), examining alternative methods to destabilize vapor barrier formation in liquid quenchants. Namely, ultrasound in combination with a brine solution is applied to realize fast yet controllable quenching conditions.

The temperature of the quenchant and the severity of the quench can significantly influence the mechanical properties, phase transformations, and hardness of steels. This study examines the influence of quenchant temperature through experimental and numerical simulations to predict temperature profiles and phase fraction distributions for AISI 4135 steel.

In this study, a single-sided carburized Almen strip made of Pyrowear 675 is used to investigate the effect of phase transformations on quench hardening distortion. Computer modeling is used to analyze the collected experimental data and demonstrate the underlying principles of distortions and residual stress.

This work aims to contribute to the optimization of the simulation process in the heat treatment industry. Cooling curves of a polyacrylate-based (ACR) polymer solution at a concentration of 9 and 12 %, using an axial flow rate of 1.30 L/min on an immersion system and a fluid temperature of 45 °C were acquired and analyzed. Air quenching was also used to compare the polymer quenching conditions.

In this work, we report the evolution of heat extraction from probes of three different geometries: flat-end, conical-end and hemispherical-end cylinders, characterized through video-recordings and cooling curves.

Oil, polymer, and gas quenching have long been used due to their effectiveness in cooling components rapidly to achieve the desired microstructure. However, they often cause distortion, complicating post-manufacturing corrections. A newer approach, Four-Dimensional Quenching (4DQ), uses high-pressure gas as the quenching medium and allows precise control over gas flow. This method significantly reduces distortion and ensures consistency across components.

This paper reviews several techniques for hardness prediction, from simple to complex, and compares the calculated results to those published previously. Using “old-school” methods based on the Grossman H-Value and Lamont charts, we predict the expected hardness for SAE 1045 and SAE 6140 round bars in three sizes: 1, 3, and 5 in. (25, 75, and 125 mm).

The aim of the present research work was to investigate tribological performance and potential of Ni-based self-lubricating claddings for high temperature forming of lightweight alloys. Laser claddings included in this investigation were based on Ni-matrix with the incorporation of 5 wt% silver and 10 wt% MoS2 as solid lubricant precursors. Tribological evaluation and testing was performed by Load- Scanner to simulate hot forming process and results compared to high performance hot work tool steel. To simulate hot forming process of forging, wire drawing and extrusion, tests were done at room and elevated temperatures (150°C and 300°C) against typical light-weight alloys, including AISI 316L stainless steel, 6xxx series Al alloy and Ti6Al4V Ti alloy and results evaluated in terms of coefficient of friction vs. load, critical loads for galling initiation and volume of adhered work material. Results show that self-lubricated claddings with incorporated MoS2 and Ag as solid lubricants in general provide lower and more stable friction as well as improved galling resistance in high temperature forming of lightweight alloys. Positive effect of self-lubricating claddings intensifies with forming temperature, degree of plastic deformation and work material tendency to galling.

Induction surface hardening is a process often used in industrial applications to efficiently increase the lifetime of components. Recently, this process has been enhanced with the inductive short time austempering process, creating a martensitic-bainitic microstructure. It is well-known that in homogeneous mixed microstructures, an optimally adjusted volume fraction of bainite can significantly increase the lifetime of the components even further. Regarding inductive short time austempering, there is a lack of knowledge in characterizing and differentiating graded microstructures, which occur due to the temperature gradients within the process. Therefore, three methods were investigated: the analysis of the grayscale profile of metallographic sections, the hardness profile and the full width at half maximum (FWHM) profile from the intensity curve (rocking curve) of the X-ray diffraction pattern. These methods were initially applied to homogeneous structures and evaluated. The findings were then transferred to graded microstructures. Finally, the graded microstructures could be differentiated both via the hardness profile and the FWHM value, while the grayscale analysis only allowed qualitative statements to be made. It became evident that both the volume fractions and their structure are crucial for subsequent mechanical characterization. Since the martensitic microstructure is easier to identify, it serves as a reliable reference for evaluating the mixed microstructure. In summary, these findings offer the foundation for further characterization of graded martensitic-bainitic mixed microstructures.

Effective heat treatment is essential for optimizing the properties of steels in various applications. Understanding the evolution of steel microstructure during intrinsic or post-heat treatment, along with managing distortions and residual stresses, is crucial for ensuring component usability. In laser-based additive manufacturing, high temperature gradients and cooling rates induce residual stresses, impacting the heat-affected zones. However, there remains a gap in understanding how stress influences precipitation during heat treatment, particularly regarding transformation-induced plasticity (TRIP), where a stress triggers deformation during phase transformation. This study aims to investigate TRIP effects during the aging of maraging steels, commonly employed in laser-based powder bed fusion. During the experiments, the steels were continuously aged under varying compression stresses. By isolating TRIP strain from total strain, the study establishes a relationship between maximum TRIP strain after phase transformation and applied stress, defining specific TRIP constants for each steel. The presence of TRIP strain has been confirmed during short time continuous aging treatments, indicating its significance even in the initial stages of the heat treatment process. While the applied stress level does not affect hardness, significant differences in maximum hardness values after aging were observed among the investigated materials. Furthermore, a comparative analysis of different maraging steels revealed a positive correlation between the TRIP constant and the amount of precipitation, and consequently, hardness. These findings confirm the role of TRIP in precipitate formation in maraging steels and provide a foundation for further understanding and predicting post-heat treatment material states.

Martensitic stainless steels are an important group of steels for applications as knives, tools & molds and highly loaded parts in the food and plastics processing industry as well as for machinery components. Their typical hardening consists of quenching and (multiple) tempering (Q&T). As many of these steels contain at least smaller amounts of retained austenite (RA) after quenching, partitioning of carbon and nitrogen from the martensite into the RA can take place during tempering, changing it from Q&T to quenching & partitioning (Q&P). This contribution provides as systematic overview of such partitioning effects on the microstructure like the amount and stability of retained austenite as well as on subsequent effects on material properties such as hardness, toughness, strength and ductility. The various effects were investigated on several steel grades and cover also the effect of variation in heat treatment parameters like austenitizing temperature, quench rate, quenching temperature, number, duration and temperature of the tempering, respectively partitioning. The results clearly show that partitioning dominates over tempering effects at temperatures up to 500°C. Higher quenching temperatures can increase the RA-content similar to higher austenitizing temperatures. Lower quench rates can reduce it due to carbide (nitride) precipitation. Rising tempering (partitioning) temperatures up to 400°C enhances the austenite stabilization. Higher amounts of RA with reduced stability promotes transformation induced plasticity (TRIP), providing the possibility to optimized ductility and tensile strength but reduces yield strength. Increased amounts of RA with sufficient stability increases impact toughness at slightly reduced hardness. Increasing the tempering temperature above 500°C in contrast promotes, after a certain nucleation time, carbide and nitride precipitation, resulting in the elimination of the retained austenite and therefore a typical tempering condition.