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.

The automotive industry has searched for alternatives to reduce the weight of vehicles without neglecting the user’s safety by using new materials. Advanced high-strength steels of complex phases are used in structural applications requiring good performance and reducing the weight of vehicles. However, these steels have shown edge cracking, known as fissure, during processing, which has become a challenge for steelmakers and other companies that rely on them to manufacture structural components. Such defects can be associated with the interaction between the different microstructural constituents of the steel, such as various phases and precipitates generated during its processing to achieve the required mechanical properties. The present work presents the studies evaluate the effect that processing and chemical composition exerts on edge cracking in complex phase steels of grade 800 MPa produced by different steelmaking routes.

A physics-based software model is being developed to predict the nitriding and ferritic nitrocarburizing (FNC) performance of quenched and tempered steels with tempered martensitic microstructure. The microstructure of the nitrided and FNC steels is comprised of a white compound layer of nitrides (ε and γ’) and carbides below the surface with a hardened diffusion zone (i.e., case) that is rich in nitrogen and carbon. The composition of the compound layer is predicted using computational thermodynamics to develop alloy specific nitriding potential KN and carburizing potential KC phase diagrams. The thickness of the compound layer is predicted using parabolic kinetics. The diffusion in the tempered martensite case is modeled using diffusion with a reaction. Diffusion paths are also developed on these potential diagrams. These model predictions are compared with experimental results.

Retained austenite may be helpful or detrimental to the life of heat-treated components, but it can be difficult to accurately measure in manufactured steels. Commonly used visual sample investigations are subjective and often incorrect, magnetic measurements require part-specific calibration, and electron backscattering involves expensive equipment, intensive sample preparation, and long measurement times. Recent developments in X-ray diffractometry, however, provide measurements in minutes and can compensate for the influence of carbides in high-carbon steels as well as texture orientations in rolled sheet metals. This paper discusses the use of X-ray diffraction for measuring retained austenite and compares and contrasts it with other methods. It also provides a brief review of the formation of austenite and its effect on carburized gears, TRIP steels, and bearings.

This paper evaluates the influence of niobium additions on the wear behavior of high-silicon steel, representative of the advanced high strength steels used in the automotive industry. It describes the alloy compositions of the test samples used, the heat treatments to which they were subjected, and the tests that were subsequently performed. It also interprets test results and outlines key findings.

The purpose of this work is to incorporate boriding and austempering treatments in a single thermal cycle and assess its effect on two high strength bainitic steels. The combined process, called boro-austempering, is a promising alternative to increase the surface wear resistance of advanced high strength steels as shown in the test results presented.

Flash Bainite Processing employs rapid thermal cycling (<10s) to strengthen commercial off the shelf (COTS) steel sheet, plate, and tubing into AHSS. In a continuous process, induction technology heats a narrow segment of the cross section in just seconds to atypically high temperatures (1000-1300°C). Quenching substantially immediately follows. Flash Processing utilizes inherent heterogeneity of steel creating multi-chemistry, complex mixtures of approximately 20% bainite and 80% martensite. Carbide dissolution and carbon migration are controlled by limiting time in the austenite temperature range. Unlike conventional heat treating to create advanced high strength steels (AHSS), homogeneity is intentionally avoided and non-equilibrium conditions are created. The leanest prior ferritic regions transform to bainite while prior pearlite forms martensite. A 7-10% higher yield/tensile strength product results with the beneficial ductility of the bainite constituent. Flashed AISI1010 (1100MPa UTS) and AISI1020 (1500MPa UTS) have shown exceptional room temperature stamp-ability to 0T/1T bend radii. The 1500MPa formability of 3G-AHSS is achievable. Flash Bainite offers simultaneous weight and cost savings.