Annealed State Research Articles

TEM Observations of the Microstructural Changes in the Interfacial Zone of Explosively Welded Titanium/Steel Before and After Ex Situ and In Situ Heat Treatment.

This paper presents the comparison of the microstructure of the interface zone formed between titanium (Ti Gr. 1) and steel (P265GH+N) in various processing stages—directly after explosive welding versus the annealing state. Transmission electron microscopy technique served as an excellent tool for studies of the sharp interface in-between the waves. Directly after the welding process in this area, a thin layer of the metastable β-Ti (Fe) solid solution was observed. In the next step, two variants of annealing have been employed: ex situ and in situ in TEM, which revealed the complete information on the interface zone transformation. The results have shown that during the annealing at 600°C for 1.5 h, the diffusion of carbon towards titanium caused the formation of titanium carbides with a layered arrangement. Compared to our previous studies, the carbides found here have a hexagonal structure. Furthermore, changes in the dislocation structure were observed, indicating the occurrence of recovery processes. Possible reasons for differences observed in the microstructure of the interface formed due to ex situ and in situ annealing are also discussed. The microstructure observations are accompanied by the microhardness measurements, which showed that the annealing caused a significant reduction in the microhardness values.

A study of the crystal structure of a Tb-Dy-Fe alloy during annealing via rietveld analysis

The crystal structure and magnetic structure of Tb-Dy-Fe compounds before and after annealing heat treatment were researched, in order to further study the influence factors on the magnetic performance besides the orientation and phases. The Rietveld method was used to refine the structural data and obtain small changes in the structure. The results confirm the existence of tetragonal and rhombohedral phases at room temperature, which is consistent with previous findings. Both samples had tetragonal structures and rhombohedral distortion structures at room temperature. The lattice constants of the rhombohedral structure were a = 5.18160 Å and c = 12.72178 Å, while the volume diagonal of the tetragonal cell was 12.69513 Å, indicating the amount of change between the two structures. The volume proportion of the hexagonal phase increased from 25% to 51% after heat treatment. The refinements made on the basis of the neutron patterns indicated that the refined Tb/Dy and Fe moments are antiparallel, while the average atomic magnetic moment of Tb/Dy increased in the annealed state compared with that in the as-cast state. By combining all the analytical results, we discussed the effect of structural distortion on the magnetostriction of Tb-Dy-Fe.

Tailoring powder strengths for enhanced quality of cold sprayed Al6061 deposits

As verified by literature, heat-treatments of as-atomized Al-alloy powders before cold spraying, result in microstructural homogenization and deposition efficiency increment. So far, a straightforward correlation between powder strength and consequences for the performance in cold spraying and deposit properties is still missing. This work thus provides reliable analyses of powder strengths in as-atomized and annealed states to the calculation of critical velocities and deposit quality parameter η, as well as the associated influences of powder strength on single-particle adhesion and deposit microstructures and properties. By annealing of as-atomized powder, its strength is reduced by about 60%, which allows decreasing the critical velocity for a successful deposition. Experimental results demonstrate that powder strength-based calculation of quality parameter η allows for a more realistic description of microstructural characteristics and deposits properties. The single-particle impact morphologies as well as the detachment features of adhering splats by cavitation tests visualize the respective deposition characteristics and bonding behaviors. The lower critical velocities by annealing contribute to better single splat adhesion, lower porosity, higher electrical conductivity, as well as improved tensile strength of deposits. The direct correlation of powder pre-annealing and strength in combination with cold spraying parameter variation allows defining effective strategies for improving deposit properties.

ВЛИЯНИЕ ТЕРМООБРАБОТКИ НА ДИНАМИЧЕСКИЕ СВОЙСТВА БЕЗОЛОВЯННОЙ БРОНЗЫ. МУЛЬТИФРАКТАЛЬНАЯ ПАРАМЕТРИЗАЦИЯ СТРУКТУР РАЗРУШЕННЫХ ОБРАЗЦОВ

The results of experimental studies of the dynamic characteristics of tinless bronze of the BrAZhNMts 9-4-4-1 brand of two types (in cold-rolled and annealed states) at different strain rates are presented. An experimental determination of the dynamic characteristics of bronze was carried out using a modification of the Kolsky method for dynamic tension using a split Hopkinson pressure bar. Tests were carried out with different strain rates up to rupture of the samples. It has been found that for both states, an increase in the strain rate leads to a significant change in the mechanical characteristics. The material after annealing showed a decrease in strength properties compared to the initial state by 20–22%. Compared to the static standard characteristics, the dynamic reduction in area has increased for both types of metal condition, and the dynamic reduction in area in the annealed state is 18–25% higher than the reduction in the cold-rolled state, i.e. in the annealed state, bronze is more ductile, which fits into the traditional theory of heat treatment. After dynamic testing, the fractured specimens were cut along the central tensile axis along the diameter so that the analytical sections (surfaces of the specimens that are ground, polished and chemically etched to reveal the structure or defectiveness of the specimens) were perpendicular to the fractures. The microstructural analysis of the destroyed samples and multifractal parametrization of their structures were carried out. On the basis of multifractal analysis in terms of the latent ordering parameter, it was found that the annealed state is less resistant to structural phase transition than the cold-rolled state. In annealed samples, a larger number of excited local regions appear, in which the hydrodynamic nature of the flow is possible and, as a result, such samples are more plastic.

Micro-addition of Fe in highly alloyed Cu-Ti alloys to improve both formability and strength

Cu-Be alloys provide excellent electrical and mechanical properties, but present serious health hazards during manufacturing. Among alternative alloys, the Cu-Ti system has the highest yield strength; however, Ti cannot be easily solutionized at concentrations above 4 wt%, resulting in a relatively low formability. In this study, Cu-xTi-yFe (x = 3, 5, 6 wt% and y = 0, 0.3 wt%) alloys were studied after both solution-annealing and age-hardening through mechanical testing and microstructure analysis. Micro-additions of Fe kept high concentration of Ti in solid solution (up to 6 wt%) after water quenching and suppressed the classical “wave-like” early-stage precipitation. Instead, a new dispersion of nano precipitates was observed. This behavior results in doubling the ductility in the solution annealed state (up to 48% elongation), together with maintaining a very high strength after ageing (up to 975 MPa) from precipitation of metastable nano α-Cu4Ti. This study shows that Fe micro-additions, when combined with a higher amounts of Ti (6 wt%), enables the production of Cu-based alloys combining high formability and strength, providing an excellent alternative to Cu-Be in mechanical applications.

Role of homogenization on tensile properties and microstructures in a dilute Mg–Zn–Ca–Mn alloy sheet

The effect of homogenization on microstructures and tensile properties in a dilute Mg–Zn–Ca–Mn alloy sheet was investigated. High-temperature homogenization at 480 °C dissolved eutectic intermetallic phases before rolling; however, there was a significant growth of αMn precipitates, resulting in a coarse grain structure in the rolled and annealed alloy sheet. Although rolling without homogenization or after low-temperature homogenization led to a slight increase in the fraction of intermetallic phases in the annealed state, fine grain structure was achieved due to finely dispersed αMn precipitates. Especially, fine average grain size of 8.9 μm was obtained without any homogenization, and the annealed sheet exhibited good 0.2% tensile yield strength and elongation to failure of 176 MPa and 23.4% along the rolling direction. Unfortunately, the annealed sheet had an in-plane yield anisotropy, but the moderate 0.2% tensile yield strength of 142 MPa could be kept even along the transverse direction due to its fine grain structure.

ABOUT THE YIELD PLATEAU UNDER SIGN-VARIABLE LOADING

During tension of samples of low-carbon steels and some other plastic materials, the sharp yield point and the yield plateau are fixed on the deformation diagram. In this case, Chernov-Luders bands appear on the surface of the sample in the local section, which then propagate along the tension axis. The physical nature of the sharp yield point is established: the drop in the load after reaching the (upper) yield limit occurs as a result of dislocations being an extraction out of the cloud of the embedded atoms and vacancies (Cottrell's cloud). At the occurrence of the sharp yield point , the plastic strain is limited to a small area. When the sample deformation increases, the plasticity zone (the yield plateau is marked on the diagram at this time) expands, and the stress-strain state in this zone becomes almost homogeneous, if we do not consider its boundary with the elastic region. At the end of the yield plateau, the entire sample experiences a uniform plastic deformation, excluding its ends (galtels). From this point on, the strain diagram shows the of material hardening; presumably, this hardening occurred from the very beginning, but was hidden under the yield plateau. This is evidenced by the resulting strain-induced anisotropy. After unloading the sample, when the plastic strain front (in the form of Chernov-Luders bands) has not yet passed through the entire sample, and the Bauschinger's effect is observed with the subsequent change in the stress sign. The fact that after the occurrence of the sharp yield point , the plastic strain is not localized in a certain volume, similar to what occurs during the neck formation, but spreads along the sample, serves as proof of the material hardening due to plastic deformation immediately after the load falls. Therefore, if the plastically deformable part of the sample did not have a hardening of the material due to the plastic strain growth, it would not be able to spread to the elastic part of the sample. This paper presents the experimental data of the sign-variable torsion of the thin-walled tubular samples of steel 45 in the annealed state. The deformation atdiagram of the occurrence and development of the yield plateau in distinct sections along the length of the test sample is obtained. The material hardening diagram hidden under the yield plateau is reconstructed using the well-known Masing's principle.

Reverse identification of constitutive parameters of Inconel 718 alloy based on analytical model and thermo-mechanical loads analysis of machined surface

Finite element simulation is able to predict cutting force, temperature, stress distribution and chip formation. Constructing a constitutive model suitable for cutting simulation can accurately describe the state of the cutting process, which plays an important role in improving surface quality as well as optimizing cutting parameters and tool geometric design. Nickel-based superalloys are widely used in aerospace due to their excellent physical and mechanical properties at high temperatures. In this study, J-C parameters reverse identification of Inconel 718 alloy was carried out in both the solution annealed state and precipitation hardened state. The average cutting force and chip thickness were obtained by conducting orthogonal cutting experiments, after which the shear angle was calculated. Through quasi-static compression experiments, the yield strength, strain hardening modulus and hardening index of the material were then obtained. Considering the influence of the cutting-edge radius on cutting force during the cutting process, the Waldorf model was introduced into the analytical model in order to describe the deformation characteristics (strain, temperature, strain rate and stress) of the primary shear zone, after which the shear force was modified. The J-C constitutive parameters of the solution annealed state and precipitation hardened state were inversely identified by the intelligent optimization algorithm. According to the given range of cutting conditions, the accuracy of the method was verified through comparison with the cutting force and chip morphology of the finite element simulation. The differences in quasi-static and cutting dynamic mechanical responses of the two states were subsequently expounded. The effects of tool wear types and cutting parameters on the material flow characteristics at the tool tip as well as the thermal-mechanical load on the machined surface of precipitation hardened state Inconel 718 alloy were analyzed via numerical simulation. Accordingly, this study may provide insight into the identification of constitutive parameters of superalloys as well as the control of machined surface quality.

Effect of heat treatment temperature on microstructure and tensile properties of austenitic stainless 316L using wire and arc additive manufacturing

The effect of heat treatment temperature on the microstructure and tensile properties of 316L stainless steel fabricated by wire and arc additive manufacturing was studied in this paper. Heat treatment was used to uniformize the microstructure, eliminate the anisotropic tensile properties in as-built 316L part, and improve the poor elongation caused by the multilayered structure of alternating re-melting area (RA) and overlapping area (OA). The results showed that the heat treatments below 1000 °C had no significant effect on the multilayered structure and columnar austenite grains, but only changed the morphology and content of ferrite and σ phase within the grains. With the increase of the heat treatment temperature, ferrite transformed into σ phase and the fraction of second phase gradually decreased, leading to the slight increase of elongation but decrease of material strength and its anisotropic degree. After solution annealing above 1000 °C, the ferrite and σ phase was nearly dissolved in the austenite matrix. The austenite recrystallized and the multilayered structure was destroyed, which played a major role in the tensile properties. With the increase of heat treatment temperature, the fraction of recrystallization increased, resulting in decrease of material strength. The elongation was greatly improved and reached that of the annealed state, and its anisotropic was almost eliminated.

Investigation of Mechanical and Magnetic Properties of Co-Based Amorphous Powders Obtained by Atomization.

Properties of Co-based alloys with high Glass Forming Ability (GFA) in the form of powder are still not widely known. However, powders of high GFA alloys are often used for the development of bulk metallic glasses by additive manufacturing. In this work Co47.6B21.9Fe20.4Si5.1Nb5% at. and Co42B26.5Fe20Ta5.5Si5Cu1% at. were developed by gas-atomization. Obtained powders in size 50–80 µm were annealed at Tg and Tx of each alloy. Then SEM observation, EDS analyses, differential thermal analysis, X-ray diffraction, nanoindentation, Mössbauer, and magnetic properties research was carried out for as-atomized and annealed states. The gas atomization method proved to be an efficient method for manufacturing Co-based metallic glasses. The obtained powder particles were spherical and chemically homogeneous. Annealing resulted in an increase of mechanical properties such as hardness and the elastic module of Co47.6B21.9Fe20.4Si5.1Nb5% at and Co42B26.5Fe20Ta5.5Si5Cu1%, which was caused by crystallization. The magnetic study shows that Co47.6B21.9Fe20.4Si5.1Nb5 and Co42B26.5Fe20Ta5.5Si5Cu1 are soft magnetic and semi-hard magnetic materials, respectively.

Phase transformations and mechanical behavior in a non-equiatomic Ti10Fe30Co30Ni30 medium-entropy alloy

Phase transformation, microstructure and mechanical behavior of a non-equiatomic Ti10Fe30Co30Ni30 medium-entropy alloy (MEA) were systematically studied in as-cast and annealing states. The as-cast MEA was composed of γ-fcc matrix, spherical ordered γ′-L12 precipitates (with an average size of ∼118 nm) and plate-like D024-structured η phase in the interdendritic (ID) regions, along with γ-fcc matrix and numerous γ′ nanoprecipitates (with an average size of ∼20 nm) in the dendrites (DR). The as-cast MEA followed by annealing at 670 °C for 8 h (denoted as AT-670 MEA) comprised irregular rod-like γ′ phase, B2-structured Fe–Co phase and lamellar-like structure consisting of parallelly elongated γ′ and B2 phase in the ID regions. In the DR regions, the AT-670 MEA also consisted of γ-fcc matrix and numerous γ′ nanoprecipitates, whereas the γ′ nanoprecipitates were noticeably coarser than those of the as-cast counterpart. The complicated phases and complex microstructures of the AT-670 MEA were principally caused by phase decompositions at intermediate temperature. Only γ-fcc matrix and needle-like γ′ precipitates could be observed after the as-cast MEA annealing at 1050 °C for 8 h (denoted as AT-1050 MEA). The formation of needle-like γ′ precipitates was attributed to the coalescence of spherical γ′ phase in the ID regions, driven by the increase of elastic stress between the γ-fcc/γ′-L12 interface during the annealing process. Among these three alloys, the AT-1050 MEA exhibits the best combination of strength and ductility, with a tensile yield strength of ∼669 MPa, an ultimate strength of ∼987 MPa and a total elongation of ∼10.9%. The present study provides an effective pathway to improve mechanical properties by tuning microstructures and phase compositions.

A Detailed Interface Characterization of the Explosively Welded Three-Layered Ti Gr 1/Alloy 400/1.4462 Steel Clads Before and After Heat Treatment

The presented research focused on the microstructural characteristics of explosively welded three-layered Ti Grade (Gr) 1/Alloy 400/1.4462 steel clads before and after heat treatment being of large practical potential. Scanning electron microscopy (SEM) analyses have shown that both interfaces formed between the plates are continuous and without defects. The in-depth examination was dedicated to the upper Ti Gr 1/Alloy 400 interface, located closer to the explosive material, therefore, subjected to more extreme welding conditions. The presence of cubic phase Ti2Ni, hexagonal phase Ni3Ti, and tetragonal phase (CuxNi1−x)2Ti were confirmed within the melted zones, which slightly widened due to annealing, being an essential step in the manufacturing of these modern materials. Transmission electron microscopy observations in the nano scale confirmed the preliminary chemical composition analyses collected with energy-dispersive X-ray spectroscopy in SEM. They additionally revealed the interface zone microstructure transformation due to the annealing. It was evidenced that initially mixed phases in the form of grains, after heat treatment formed irregular bands arranged in the following sequence: Alloy 400/Ni3Ti/(CuxNi1−x)2Ti/Ti2Ni/Ti Gr 1. A clear segregation of Cu and Ni forming two separate layers was also noticed. These diffusion phenomena may influence the strength of the final product, therefore need further studies regarding the prolonged annealing state.

Production of low-scandium Al – Mg alloys

The work was performed at the laboratory plant of semi-continuous casting of ingots (LPSCC) of the Institute of non-ferrous metals and materials science of SFU in order to obtain deformed semi-finished products with specified performance characteristics. The paper presents the results of obtaining an Al – Mg alloy doped with zirconium and scandium. Experimental rolling ingots were cast using casting modes that provide the structure parameters of the cast billet as close as possible to the parameters obtained in industrial conditions for ingots with a thickness of at least 300 mm. This paper presents the modes of two-stage diffusion annealing. The modes of hot and cold rolling of the experimental alloys obtained at the laboratory plant of semi-continuous casting of ingots are given. he paper presents the microstructure of the studied alloys in the cast and annealed state. The paper presents the results of research on the strength and plastic characteristics of deformed semi-finished products from experimental ingots of Al – Mg alloy with a scandium content of less than 0.1 %. The article presents comparative studies of six experimental alloys with an average content of the variable element Sc from 0.054% to 0.075%, respectively. The article shows that when the average concentration of Sc decreases to 0.054%, it is not possible to achieve the specified level of mechanical properties, due to the insufficient total concentration of the alloying element (Sc) in experimental alloys, which provides the effect of quench age hardening during the decomposition of solid solutions of scandium with the formation of intermetallic Al3Sc. It was shown that it is possible to reduce the concentration of scandium in the composition of Al–Mg alloys to 0.075% with the achievement of high performance characteristics: not lower than tensile strength — 390 MPa, proof strength — 275MPa, percentage of elongation — 12 %. The research was carried out within the framework of the State assignment by the laboratory of low-carbon metallurgy and power engineering of Siberian Federal University, as a participant company of REC «Yenisei Siberia» within the national project “Science and universities”.

The Effect of Sn Addition on Zn-Al-Mg Alloy; Part I: Microstructure and Phase Composition.

In this study, the addition of Sn on the microstructure of Zn 1.6 wt.% Al 1.6 wt.% Mg alloy was studied. Currently, the addition of Sn into Zn-Al-Mg based systems has not been investigated in detail. Both as-cast and annealed states were investigated. Phase transformation temperatures and phase composition was investigated via DSC, SEM and XRD techniques. The main phases identified in the studied alloys were η(Zn) and α(Al) solid solutions as well as Mg2Zn11, MgZn2 and Mg2Sn intermetallic phases. Addition of Sn enabled the formation of Mg2Sn phase at the expense of MgxZny phases, while the overall volume content of intermetallic phases is decreasing. Annealing did not change the phase composition in a significant way, but higher Sn content allowed more effective spheroidization and agglomeration of individual phase particles.

The Effect of Sn Addition on Zn-Al-Mg Alloy; Part II: Corrosion Behaviour.

Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure spheroidisation in the annealed samples, potential intergranular corrosion paths are significantly reduced. Samples with 0.5 wt.% of Sn showed the best corrosion properties. The main corrosion products identified by XRD analysis for all samples were simonkolleite and hydrozincite. Occasionally, ZnO and AlO were identified in limited amounts.

Degradation Analysis of Thin Mg-xAg Wires Using X-ray Near-Field Holotomography

Magnesium–silver alloys are of high interest for the use as temporary bone implants due to their antibacterial properties in addition to biocompatibility and biodegradability. Thin wires in particular can be used for scaffolding, but the determination of their degradation rate and homogeneity using traditional methods is difficult. Therefore, we have employed 3D imaging using X-ray near-field holotomography with sub-micrometer resolution to study the degradation of thin (250 μm diameter) Mg-2Ag and Mg-6Ag wires. The wires were studied in two states, recrystallized and solution annealed to assess the influence of Ag content and precipitates on the degradation. Imaging was employed after degradation in Dulbecco’s modified Eagle’s medium and 10% fetal bovine serum after 1 to 7 days. At 3 days of immersion the degradation rates of both alloys in both states were similar, but at 7 days higher silver content and solution annealing lead to decreased degradation rates. The opposite was observed for the pitting factor. Overall, the standard deviation of the determined parameters was high, owing to the relatively small field of view during imaging and high degradation inhomogeneity of the samples. Nevertheless, Mg-6Ag in the solution annealed state emerges as a potential material for thin wire manufacturing for implants.

Design and development of Co35Cr5Fe20−xNi20+xTi20 High Entropy Alloy with excellent magnetic softness

The design and development of excellent soft magnetic materials are fascinating research areas in materials science. A series of Co35Cr5Fe20−xNi20+xTi20 (x = 5, 10, 15) High Entropy Alloys (HEAs) were synthesized through mechanical alloying (MA) technique and heat-treated at two different temperatures at 200 °C and 700 °C for 2 h. The XRD analysis confirmed that the HEAs comprised of face-centered cubic (fcc) phase and a minor fraction of an intermetallic R-phase at as-synthesized and annealed state. SEM-EDS observation confirmed the homogeneous compositional distribution and showed that after annealing at 700 °C, tiny spherical particles precipitated over the large grains. The synthesized HEAs showed soft magnetic behavior with low coercivity (12–16 Oe). However, the coercivity decreased more than five times to the initial value after the annealing at 700 °C. Co35Cr5Fe10Ni30Ti20 HEA annealed at 700 °C shows excellent soft magnetic properties with a high value of Ms (78.01 emu/g) and an extremely low value of Hc (1.7 Oe). The found value of the coercivity is the lowest value of the coercivity reported so far for the case of magnetic CoCrFeNiTi based HEAs. In addition, the present work provides a novel design strategy for the development of magnetic HEAs with excellent magnetic softness.

Step-wise R phase transformation rendering high-stability two-way shape memory effect of a NiTiFe-Nb nanowire composite

In this work, we designed a NiTiFe-Nb nanowire composite to achieve a high-stability and small-hysteresis R phase two-way shape memory effect (TWSME). The R-phase TWSME was achieved in the composite in an annealed state without thermomechanical training due to the inherent internal stresses associated with the Nb nanowires, as demonstrated by in situ synchrotron high-energy X-ray diffraction. Transmission electron microscopic analysis also revealed some details of the R-phase transformation process, which render an explanation of the high cyclic stability of the R-phase TWSME. The R-phase transformation in this NiTiFe-Nb nanowire composite was found to proceed over several stages, including the formation of precursor nanodomains of partial lattice distortion for the R phase, the formation of R phase particles of coordinated orientations, the coalescence of the R phase particles into selected plate variants of preferential orientations for TWSME, and the continued evolution of the R phase crystallographic structure for further TWSME with zero hysteresis. Such step-wise process of the R-phase transformation divides the total TWSME strain into segments of smaller magnitudes in the macroscopic behavior, and more importantly reduces the discrete lattice distortion mismatch at the transformation interface on the microscopic scale. This drastically reduces the chances of generating dislocations during the transformation process, thus rendering the high cyclic stability of the R-phase TWSME. Such intricate behavior may be closely related to the unique NiTiFe matrix – Nb nanowire microstructure and its unique inherent internal stress condition.

Corrosion Resistance of 18Ni-300 maraging steel manufactured by LPBF

The study describes the corrosion behaviour of LPBF parts made of MAR 300 (EN 1.2709) in sulphuric acid. It includes the influence of the heat treatment on the part’s properties as solution annealed and age hardened with reference to conventional samples. Laser remelted surfaces were examined as well. Due to the layered production of AM components, which is characteristic for this process, high surface roughness occurs. Therefore, for many applications and mostly on functional surfaces, complex post-processing of the surfaces is necessary. The reliable use of the manufactured components, demand knowledge of the specific influence of the selected post-processing methods on the electrochemical behaviour. The corrosion investigation takes place on different sample surfaces, such as milled, turned, sandblasted, untreated, grinded and laser-machined. The results show that there is no correlation between surface treatment and corrosion resistance. However, an increase in corrosion rate due to age hardening of the material can be observed for both LPBF and conventionally produced samples. By laser surface remelting of these age hardened samples, the corrosion resistance of these parts could be increased again, to the same level as in the solution annealed state.

Influence of Cutting Parameters on the Service Life of Twist HSS Drill Bit When Drilling C35 Steel

This work aims to understand the influence of cutting parameters on the twist high-speed steel (HSS) drill bits wear when drilling C35 steel before and after quenching. An experimental investigation has been conducted using the planning experience methodology (L8) on C35 steel in the annealed and hardened states. The input parameters are cutting regime elements, cutting speed (Vc), feed rate (f), and drill diameter (D), while the output parameters are the tool wear related to its tool life. The most interesting phenomenon is the controversial effect of cutting speed when drilling C35 steel in hardened conditions. The drilling life increases with increasing cutting speed for different cutting regimes (1 to 8). In addition, the 20 mm diameter drill related to the high value of the depth of cut (f) has given better life before and after hardening, contrary to the literature on cutting tool life. The analysis of variance (ANOVA) has showed that the feed rate (f) is the most significant factor in the annealed state while it is the depth of cut (ap) in the hardened state. The correlation coefficients R2 determined by the ANOVA before, and after quenching, are very satisfactory, and testify the good adequacy of the proposed model.