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For nowadays construction purposes, it is necessary to define the life cycle of elements with defects. As steels 42CrMo4 and 41Cr4 are typical materials used for elements working under fatigue loading conditions, it is worth to know how they will behave after different heat treatment. Additionally, typical mechanical properties of material (hardness, tensile strength, etc.) are not defining material’s fatigue resistance. Therefore, it is worth to compare, except mechanical properties, microstructure of the samples after heat treatment as well. The paper aims to discuss these issues.

Samples of normalized 42CrMo4 (and 41Cr4) steel were heat treated under three different conditions. All heat treatments were designed in order to change microstructural properties of the material. Fatigue tests were carried out according to ASTM E647-15 standard using compact tension specimens. Later on, based on obtained results, coefficients C and m of Paris’ Law for all specimens were estimated. Similar procedure was performed for 41Cr4 steel after quenching and tempering in different temperatures.

The influence of heat treatment on the fatigue crack growth rates (42CrMo4, 41Cr4 steel) has been confirmed. The higher fatigue crack growth rates were observed for lower tempering temperatures.

This study is associated with influence of microstructural properties of the material on its’ fatigue fracture. The kinetic fatigue fracture diagrams have been constructed. For each type of material (and its heat treatment), the Paris law constants were determined.

The combined numerical-experimental approach has been presented. The purpose of this paper is to determine the critical rupture load of the notched components based on the cohesive zone modeling (CZM).

The 42CrMo4 steel (in normalized state) state has been tested and modeled using an eXtended finite element method (xFEM) philosophy with the CZM approach. In order to validate the numerically obtained critical load forces the experimental verification was performed.

The critical loads were determined for various notch configurations. The numerical and experimental values were compared. Based on this, a good agreement between experimental and numerical data is achieved. The relative error does not exceed 7 percent.

The presented procedure and approach is effective and simple for engineering applications. It is worth to underline that the obtained critical load values for notched components require only the static tensile test results and implementation of the presented route in numerical FEM, xFEM environment.

The presented methodology is actual and still developed. The scientific and engineering value of the presented numerical procedure is high.

The purpose of this paper is to study the influence of multiaxial loading composed with different frequencies between the axial and torsional components in 42CrMo4 concerning fatigue life and early crack growth orientation.

Biaxial fatigue tests were carried out by a biaxial servo‐hydraulic machine, considering different loading paths and different frequencies between the normal and shear stress components in 42CrMo4. Theoretical estimations for fatigue life and early crack growth orientation were performed by applying various critical plane models. In addition, fractographic analysis of the fracture surfaces was carried out. The estimated results are compared with experimental results.

Significant effects were observed of the different frequency between the axial and torsion components on fatigue life and early crack growth orientation. The critical plane models based on shear mode give better estimations when compared with experimental results.

The paper shows that improved fatigue design can be achieved by considering the influence of different frequencies in multiaxial loadings.

The purpose of this paper is to study the influence of the cutting conditions (cutting speed, feed rate and cutting depth) on the roughness (Ra) and on the flank wear (Vb) of the steel AISI 4140.

Mixed ceramic (CC650) and polycrystalline cubic boron nitride (PCBN) have been used to carry out straight turning tests under dry conditions.

The results indicate that PCBN is more efficient than mixed ceramic (Al2O3+TiC) used in terms of wear resistance regardless of the aggressiveness of the AISI 4140 at 50 hardness rockwell (HRC). Consequently, it is the most powerful. Surface quality attained with PCBN tool considerably compares with that of grinding. Even when the tool wear VB reached 0.3 mm, the majority of the recorded Ra values did not exceed 1 m at the various speeds tested. The correlation of tool wear Vb and surface roughness Ra established allows obtaining experimental empirical data on the cutting tool wear from measured surface roughness for practical use in industry. The values of constants and the coefficient of determination R² of this mathematical model will be calculated. Mathematical models expressing the relation between the elements of the cutting regime and technological parameters (tool life and roughness) are proposed.

Many works have been already made in the similar manner, but this study of CC650 and PCBN wear is the first. Through this study, we propose a mathematical model expressing the relation between the elements of the cutting regime, tool life and roughness.

We discuss a model that is capable of describing the solid‐solid phase transitions in steel. It consists of a system of ordinary differential equations for the volume fractions of the occuring phases coupled with a nonlinear energy balance equation to take care of the latent heats of the phase changes. This model is applied to simulate surface heat treatments, which play an important role in the manufacturing of steel. Two different technologies are considered: laser and induction hardening. In the latter case the model has to be extended by Maxwell’s equations. Finally, we present numerical simulations of laser and induction hardening applied to the steel 42CrMo4.

The purpose of this study is to determine the effects of post-annealing and post-tempering processes on the microstructure, mechanical properties and corrosion resistance of the AISI 304 stainless steel gas metal arc weldment.

Gas metal arc welding of AISI 304 stainless steel was carried out at an optimized processing condition. Thereafter, post-annealing and post-tempering processes were performed on the weldment. The microstructure, mechanical and electrochemical corrosion properties of the post-weld heat treated samples, as compared with the as-welded, were investigated.

The as-welded joint was characterized with sub-granular grain structure, martensite formation and Cr-rich carbides precipitates. This made it harder than the post-annealed and post-tempered joints. Because of slower cooling in the furnace, the post-annealed joint contained Cr-rich carbides precipitates. However, the microstructure of the post-tempered joint is more refined and significantly devoid of the carbide precipitates. Post-tempering process improved the elongation (∼23%), tensile (∼10%) and impact (∼31%) strengths of the gas metal arc AISI 304 stainless steel weldment, while post-annealing process improved the elongation (∼20%) and impact strength (∼72%). Owing to the refined grain structure and significant elimination of the Cr-rich carbide precipitates at the joint, the post-tempered joint exhibited better corrosion resistance in 3.5 Wt.% NaCl solution than the post-annealed and the as-welded joints.

The appropriate post-weld heat treatment that enhances microstructural homogeneity and quality of the AISI 304 gas metal arc welded joint was determined.

The purpose of this paper is to develop a finite element method (FEM) supported simulation of drilling process applied to superficially hardened steels and assess the heat treatments effect on the optimum drilling conditions (feed rate, speed, etc.).

A three-dimensional model was developed simulating the drilling procedure while experimental data, concerning the chip geometry and force components, were used to validate the model. The developed simulation will allow systematically insight on the tools wear progression induced by the developed temperature and stress fields. Two different cases of simulation were examined. A typical simulation was investigated, which erected with all the standard features found in the FEM simulation software. In the second case, all the experimental data were introduced.

The simulation results revealed that the advanced developed FEM model describes sufficiently the real chip geometry. Moreover, the FEM calculations provide an effective tool for predicting occurring temperatures, strain and stresses and thus for approaching the real loads of the cutting tool during drilling.

This paper fulfills an identified need to study the drilling simulation.

Reliable modeling of induction hardening requires a multi-physical approach, which makes it time-consuming. In designing an induction hardening system, combining such model with an optimization technique allows managing a high number of design variables. However, this could lead to a tremendous overall computational cost. This paper aims to reduce the computational time of an optimal design problem by making use of multi-fidelity modeling and parallel computing.

In the multi-fidelity framework, the “high-fidelity” model couples the electromagnetic, thermal and metallurgical fields. It predicts the phase transformations during both the heating and cooling stages. The “low-fidelity” model is instead limited to the heating step. Its inaccuracy is counterbalanced by its cheapness, which makes it suitable for exploring the design space in optimization. Then, the use of co-Kriging allows merging information from different fidelity models and predicting good design candidates. Field evaluations of both models occur in parallel.

In the design of an induction heating system, the synergy between the “high-fidelity” and “low-fidelity” model, together with use of surrogates and parallel computing could reduce up to one order of magnitude the overall computational cost.

On one hand, multi-physical modeling of induction hardening implies a better understanding of the process, resulting in further potential process improvements. On the other hand, the optimization technique could be applied to many other computationally intensive real-life problems.

This paper highlights how parallel multi-fidelity optimization could be used in designing an induction hardening system.

The purpose of this study is to optimize input parameters of particle size and applied load to determine minimum weight loss and friction coefficient for Al2O3/SiC particles-reinforced hybrid composites by using Taguchi’s design methodology.

The experimental results demonstrate that the applied size is the major parameter influencing the weight loss for all samples, followed by particle size. The applied load, however, was found to have a negligible effect on the friction coefficient. Moreover, the optimal combination of the testing parameters was predicted. The predicted weight loss and friction coefficient for all the test samples were found to lie close to those of the experimentally observed ones.

The optimum levels of the control factors to obtain better weight loss and friction coefficient were A8 (particle size, 60 μm) and B1 (applied load, 20 N), respectively. Taguchi’s orthogonal design was developed to predict the quality characteristics (weight loss and friction coefficient) within the selected range of process parameters (particle size and applied load). The results were validated through ANOVA.

Firstly, hybrid MMCs ceramic powders were produced and then mechanical tests and optimization were performed.

The aim of the current research is to characterize boride coatings on steels and steel alloys produced in a CVD fluidized bed reactor.

Heat treatments of alloys in fluidized bed reactors have been carried out for more than 25 years. Recently, this technology has been used for surface engineering applications in the deposition of hard and/or corrosion‐resistant layers. The present paper used fluidized bed technology (FBT) to deposit boride coatings on to ferrous materials. The coatings were examined by means of optical microscopy, Vickers microhardness measurements and X‐ray diffraction in terms of coating thickness and morphology, phase formation and hardness determination. The coating's tribological properties were evaluated under dry wear. Impact tests were also carried out to determine the fatigue resistance of the examined coatings under dynamic impact loading.

Boriding in a fluidized bed reactor is a simple, environmentally friendly and fast‐coating process. The produced iron‐boride coatings are characterized by excellent quality and uniform tooth‐shaped morphology. Fe₂B was the predominant boride phase formed, exhibiting superior tribological properties under dry wear conditions. Impact testing investigations revealed high‐fatigue strength of boride coatings in combination with limited deformable substrates.

The investigated coatings were deposited only on some structural and tool steel substrates.

Boride coatings deposited using FBT are satisfactory abrasive wear‐ and fatigue‐resistant coatings in comparison with those produced using common boride coating methods.

The outcome of the research is of great importance for the industry using abrasive wear coatings.