Microhardness Measurements Research Articles

Evaluation of Recycled and Reused Metal Powders for DMLS 3D Printing

Metal powders for additive manufacturing are expensive, and producing new ones from mined metals has a negative ecological impact. In this work, recycled and reused metal powders from MS1 steel for direct metal laser sintering (DMLS) 3D printing were evaluated in the laboratory. The powders were recycled by melting followed by gas atomizing. Virgin, recycled, and reused metal powders were evaluated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), metallography analysis, microhardness measurements, particle size distribution (PSD), shape factor by digital image processing (DIP), and flowability testing. The results showed that the particle distribution was modified after recycling. Kurtosis analysis revealed a reduction from −0.64 for virgin powders to −1.29 for recycled powders. The results demonstrated a positive skewness, indicating that the recycled powder contained a greater proportion of smaller particles. The shape factor was also modified and changed from 1.57 for virgin powders to 1.28 for recycled powders. The microstructure also changed, and austenite was found in the recycled powders. The microhardness of recycled powder decreased by 39% compared to the virgin powder. Recycled powders did not flow, using two different funnels to evaluate their flowability. The flowability of used powder was reduced from 4.3 s to 2.9 s.

Effect of Indenter Load on Vickers Microhardness and Indentation Depth of One Resin Composite

The load and size of the indentation may affect the hardness value. This study investigated the effect of the indentation size on the microhardness of one resin-based composite (RBC). Metal molds 4 mm deep and 12 mm in diameter were filled with Tetric EvoCeram Bulk Fill (Ivoclar) and light-cured for 10 s using a broad-spectrum LED curing light. The Vickers microhardness and the degree of conversion (DC) at the top and bottom surfaces were measured 24 h later before and after polishing the RBC. The microhardness measurements were made using 50, 100, 300 and 1000-gf loads with the same 8 s dwell time. The DC was measured in the same region using mid FT-IR spectroscopy. Repeated measures analysis of variance tests were used to determine if the surface (top vs. bottom) or the indenter loads had a significant effect on the VH, or if polishing affected the VH and the DC (alpha = 0.05). It was found that the indenter load did not affect the Vickers hardness of the unpolished top surface (p = 0.759), the polished top surface (p = 0.374), or the polished bottom surface (p = 0.083) of the Tetric EvoCeram Bulk Fill. Increasing the indenter load did increase the VH of the unpolished surface at the bottom (p < 0.0001). Polishing increased the DC by 13.5% at the top and by 46.7% at the bottom surface.

Искажение геометрии, окисление кромки, структурные изменения и морфология поверхности реза листового проката толщиной 100 мм из алюминиевых, медных и титановых сплавов при плазменной резке на токе обратной полярности

The introduction describes the feasibility of using reverse polarity plasma cutting to produce large-sized non-ferrous metal blanks up to 100 mm thick. Data on the use of plasma cutting with direct and reverse polarity currents for thick sheet metal and the main technological problems associated with its implementation are presented. The purpose of the work is to study the organization of the structure and properties of the near-surface zone, changes in the chemical and phase composition when cutting aluminum, copper and titanium alloys. The research methods are optical and scanning electron microscopy, microhardness measurement, X-ray diffraction and energy-dispersive analysis. Plasma cutting was carried out using air as a plasma-forming and shielding gas, simultaneously with water injection into the discharge chamber and the formation of a “water fog” around the plasma column. Results and discussion. It is shown that both the arc stability and the shape of the plasma column are of great importance in reverse polarity plasma cutting of rolled sheets. The distortion of the cutting geometry during normal operation is greatest in the central part, and with insufficient heat input it shifts to the lower part and increases significantly. The operation of the plasma torch in air does not lead to significant changes in the composition of the cutting surface of aluminum and copper alloys. A decrease in the magnesium content near the edge is typical for the aluminum alloy in the surface layers. Cutting of the titanium alloy is accompanied by intense oxidation of the surface, especially in areas of difficult metal displacement from the cutting cavity. The formation of titanium oxides, mainly rutile Ti2O, sharply increases the microhardness values in the surface layers, which negatively affects the machinability of the cutting edge and requires shot blasting to remove the oxide layer. The conclusion describes the main patterns of implementing reverse polarity plasma cutting of sheet metal from aluminum, copper and titanium alloys with a thickness of 100 mm.

Structure and Mechanical Properties of a Titanium–8 wt.% Gallium Alloy

This paper describes a study of the microstructure and mechanical properties of a titanium–gallium (Ti-8 wt.% Ga) alloy using X-ray diffraction, optical metallography, micro-hardness measurements, compression and tensile testing, nanoindentation and ultrasonic velocity measurements. X-ray diffraction has shown the alloy to be wholly α Ti with no other phases present. A comparison of the hardness and elastic modulus values of the Ti-8Ga alloy with those of Ti-6Al-4V showed the former to have a significantly higher hardness, although the elastic moduli of the two alloys were broadly comparable. The study also indicated reasonable agreement between the elastic moduli obtained by nanoindentation, ultrasonic velocity measurements and tensile testing. Under compressive loading, the mean 0.2% proof stress values of the Ti-8Ga alloy were between 1066 MPa and 1083 MPa. However, under tensile conditions, the mean tensile strength was found to be only 427 MPa, and the alloy exhibited highly brittle behaviour, with specimens failing before they had undergone any appreciable plasticity. The cause of this was ascribed to high oxygen and nitrogen levels.

Functionally graded material for improved wear resistance manufactured by directed energy deposition

AbstractProtecting components against wear and corrosion is a common way to improve their lifetime. This can be achieved by coating them with a hardfacing material. Common coatings consist of materials such as tungsten carbide or cobalt-chromium alloys, also known as Stellite. Hardfacing materials can be deposited by welding methods like plasma welding or laser cladding. The discrete change of the base material to the hardfacing layer can lead to cracks and chipping. Studies showed a reduced risk of cracking when a functionally graded material is used to create a smooth transition between the base and the hardfacing. Gradings from austenitic steel to cobalt-chromium alloys are already known in the literature. However, there is no knowledge about austenitic- ferritic duplex steels as base material. Therefore, this study aims to demonstrate the feasibility of a functionally graded material from duplex steel to cobalt-chromium alloy with a new approach. By using powder-based directed energy deposition, a graded material with smooth material transition is manufactured additively. Cracking and porosity are examined through metallography. Microhardness measurements as well as the analysis of the chemical composition by energy dispersive X-ray spectroscopy and X-ray fluorescence are used to validate the build-up strategy.

Experiments and numerical simulations on fatigue properties of laser shock peening for FV520B steel

Laser shock peening (LSP) experiments, low cycle fatigue experiments, microhardness and residual stress measurements, and scanning electron microscopy (SEM) analyses were conducted on FV520B steel cylindrical specimens. Additionally, ABAQUS software was employed to predict fatigue life following the LSP process. The experimental results indicate that the surface compressive residual stresses induced by LSP inhibit both the initiation and propagation of fatigue cracks effectively, thereby prolonging the fatigue life of FV520B steel. The fatigue life of specimens at strain amplitudes of ± 0.5 %, ±0.6 %, ±0.7 %, and ± 1.0 % is improved by 132.2 %, 0.4 %, 18.0 %, and 88.8 %, respectively. A residual stress of −90 MPa is measured on the surface of the specimen and the surface hardness value increase by 48 % after LSP. The SEM results reveal that the characteristic of single crack sources for crack initiation is presented after LSP. The results of single point LSP simulation using ABAQUS demonstrate that the circumferential surface experiences a lower compressive residual stress of 30 MPa compared to a higher value of 45 MPa on the planar surface, this discrepancy arises due to rapidly decay associated with reduced rebound tensile strain on convex surfaces. A “multi-point continuous shock” simulation strategy was implemented for modeling LSP effects on the circumferential surface. The average compressive residual stress achieved was found to be 92 MPa, additionally, tensile residual stresses ranging from 8 MPa to 29 MPa were detected within secondary surfaces and inside the cylinder. Notably, discrepancies between simulated and experimental fatigue lives for LSP specimens across strain amplitudes of ± 0.5 %, ±0.6 %, ±0.7 %, and ± 1.0 % were minimal-ranging only between 10.4 % and 22.3 %.

Microstructure Development of Powder-Based Cu Composite During High Shear Strain Processing

Commercially pure Cu features excellent electric conductivity but low mechanical properties. In order to improve the mechanical properties of Cu, strengthening elements can be added to prepare alloys or composites featuring enhanced performances. This study focuses on the detailed characterization of the microstructure of a Cu composite strengthened with Al2O3 particles during high shear strain processing. The Cu-Al2O3 mixture was prepared by powder metallurgy and directly consolidated by the intensive plastic deformation method of hot rotary swaging. Samples cut from the consolidated piece were further processed by the severe plastic deformation method of high pressure torsion (HPT). The primary aim was to investigate the effects of varying degrees of the imposed shear strain, i.e., the number of HPT revolutions, microstructure development (grain size and morphology, texture, grain misorientations, etc.) of the consolidated composite; the microstructure observations were supplemented with measurements of Vickers microhardness. The results showed that the added oxide particles effectively hindered the movement of dislocations and aggravated grain fragmentation, which also led to the relatively high presence of grain misorientations pointing to the occurrence of residual stress within the microstructure. The high shear strain imposed into (the peripheral region of) the sample subjected to four HPT revolutions imparted equiaxed ultra-fine grains and an average Vickers microhardness of more than 130 HV0.1.

Archaeometallurgical investigation of the Nebra Sky Disc

The world heritage object Nebra Sky Disc is one of the best investigated archaeological objects. The origin of the raw materials it is made of is well known. However, its manufacturing process was not completely clear. Investigations were made in order to clarify the steps of manufacturing from the initial casting to the finished disc using the latest metallographic techniques. Therefore, a small piece from the outer part of the disc was investigated and compared with a replica. Both were prepared regarding the metallographic procedure. Microstructural analysis was made by optical microscopy on a colour etched surface, EDS and electron backscatter diffraction. For the investigation of mechanical properties microhardness measurements were made. It could be found that the Nebra Sky Disc was manufactured from a flat cast followed by hot forging process. During the forging process the disc was heated and forged for approximately 10 times.

CORROSION RESISTANCE OF BRAKE DISCS AFTER NITRIDING

The article presents the work carried out to create a surface layer, ultimately on cast iron brake discs, by theZeroFlow method using regulated gas nitriding. The presented research is aimed at creating a nitrided layerwith corrosive wear resistance maintained at the stage of brake disc manufacture, waiting for sale of a newvehicle, and even during further exploitation. Examples of nitriding parameters enabling such treatment ofbrake discs made of flake cast iron are presented. The research also includes measurements of the roughnessof the working areas of brake discs before and after nitriding. The properties of the nitrided layers producedare assessed following microscopic observations and microhardness measurements using the Vickers method.The impact of nitrided layers on corrosive wear is also analyzed by observing the behavior of the surfaces ofthe tested discs in a corrosive environment in the so-called “corrosion experiment.”

Microstructure and Texture Evolution of X85MnAl29-9 Steel During Aging.

The research presented in this paper is part of a larger project concerning high-manganese alloys with different chemical compositions (mainly in manganese content from 21 to 31 wt.%). The presented examination results concern the analysis of the microstructure and textures in high-manganese X85MnAl29-9 steel, an age-hardenable steel, during aging at 550 °C for various times. X85MnAl29-9 steel was first hot rolled and subsequently cold rolled up to a 30% reduction. The samples were aged after deformation at 550 °C for various times in an argon atmosphere and cooled in air. The studies include X-ray phase analysis, texture measurement and observation of the microstructure by light microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), as well as microhardness measurement. Research using scanning and transmission electron microscopy identified carbides in the analyzed samples. The results indicate that, when aging takes place, precipitation of κ'-carbide in an austenitic matrix and carbide κ at grain boundaries occurs. The appearance of satellites on diffraction patterns suggests that (Fe, Mn)3AlC nano-carbides are formed within the austenite matrix by a spinodal decomposition mechanism after the alloy is subjected to long-term aging, which is a key element for structure analysis in the design of safety systems. The use of shorter aging times (up to 24 h) leads to an increase in hardness caused by the precipitation of small κ'-carbide particles in the matrix. However, long aging times (100 h) lead to an increase in the precipitation of the carbide phase (κ and κ'), i.e., the steel becomes overage, which results in a decrease in hardness.

Investigation on micro-mechanics properties of machined metamorphic layer based on crystal plasticity finite element method

Surface materials endure significant mechanical and thermal loads during machining, leading to microstructural changes and the formation of metamorphic layers. These layers exhibit altered crystallographic characteristics, such as grain size, misorientation angles, and dislocation density, resulting in mechanical properties that differ from the bulk material. This study examines the microstructural evolution of the metamorphic layer using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). Based on microstructure characterization, a 3D reconstruction method was developed using a representative volume element (RVE). The crystal plasticity finite element method (CPFEM) was employed to establish the relationship between the microstructure and micromechanical properties, including microhardness, elastic modulus, and yield stress. The proposed method was validated by comparing simulation results with experimental data obtained from micro-pillar compression tests and nanoindentation tests. The results demonstrated a strong correlation in stress-strain curves, and the microhardness measurement error at indentation depths of 400 nm was less than 10 %.

Mechanical and surface characterisation of additively manufactured polyetheretherketone for the tribo test

Purpose The additive manufacturing process, such as fused filament fabrication based on material extrusion, fabricates the samples layer-by-layer. The various parameters in the process significantly affect the dimensions, structure and mechanical properties of the fabricated parts. The purpose of this paper is to investigate the surface and mechanical properties that can affect the contact characteristics with other materials during tribological tests. Design/methodology/approach The investigation of 3D-printed Polyetheretherketone (PEEK) includes the measurement of dimensions, microhardness, surface roughness, surface energy and tensile strength to define material characteristics. The crystallinity is measured using an X-ray diffractometer to understand the hardness behaviour. Findings The printing parameters affect its surface roughness, hardness and crystallinity. This change in parameters such as layer thickness and infill density impacts mechanical properties such as hardness and surface roughness, which will influence the contact mechanism with the counter body during any tribological test. The change in a single parameter during the sample fabrication and the change in the surface and mechanical properties are observed. Research limitations/implications The material cost plays an important role in conducting numerous destructive tests, which is a major limitation to conducting parameter optimisation by varying more parameters. The study is limited to the as-fabricated samples rather than finished samples and without any heat treatment. Achieving optimal parameters is integral to the success of additive manufacturing, ensuring the production of components with consistent performance. Practical implications The study aims at the application of 3D-printed PEEK for bush or journal bearings that can be directly used in practice. The mechanical properties discussed in this paper can fill the gap between theory and practice. Social implications The research provides all fundamental properties, including the printing parameters and their effect on the dimensions and surface structure, which are required to understand the material and its use. The results are consistent as at least four samples were tested for tribological behaviour. The conclusion is updated as per suggestions. Originality/value The study outlines the relationship between the change in layer thickness and infill density with changes in surface energy, surface roughness, hardness and tensile strength. The deformation and adhesion during the friction test depend on these properties.

Evaluation of Structural Transition Joints Cu-Al-AlMg3 Used in Galvanizer Hangers

The paper deals with the evaluation of the quality of Cu-Al-AlMg3 structural transition joints (STJ) made by explosion welding proposed for the renovation of galvanizer hangers. The three-layer joint consisted of electrolytic copper with a thickness of 25 mm, 2 mm of aluminium represented by the AW1050 alloy, and 25 mm of the EN AW 575 aluminium alloy. Light microscopy analysis confirmed the wavy pattern of both interfaces of the welded joint and significant plastic deformation in close proximity to the waves. Microhardness measurement revealed a partial strain hardening of the AW5754 copper-aluminium alloy near the interface and a significant increase in microhardness in the vortex zone of waves, reaching a value of up to 863 HV 0.025. Microcracks were also observed in these places. The intermetallic phase Al2Cu was identified in the vortex zones by XRD analysis. As a continuous layer of intermetallic phase was not observed in the interface of the welded joint, it is possible to consider the used welding parameters as appropriate. A semi-quantitative EDX analysis revealed a diversity of chemical composition in the vortex zones, which does not correspond to the phase composition based on the equilibrium binary Al-Cu diagram due to non-equilibrium conditions in the formation of the welded joint interface. The bond strength of three-layer welded joint evaluated by the strength test ranged from 151 to 171 MPa, which represented approximately a two-fold increase in comparison to the ultimate tensile strength of alloy AW1050, while the failure occurred in all samples at the AW1050-AW5754 alloy interface.

Evaluation of Different Blending Methods to Obtain Copper Composites with Graphene Oxide

This study evaluated mixing methods for producing graphene oxide-reinforced copper matrix composites aiming for a better dispersion of graphene oxide in the composite, using powder metallurgy techniques. The compacted specimens were prepared by four different mixing processes that employed either a mechanical stirrer, rotary evaporator, tip ultrasound, or ultrasound process followed by mechanical stirring. Characterizations were performed using optical microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, compression tests, Vickers microhardness, and electrical conductivity measurements. The results indicate that the combined method yields a more homogeneous microstructure and superior mechanical properties, while electrical conductivity was maintained at a level higher than that achieved by the other methods.

Effect of Temperature Control and Rotational and Traverse Speeds on the Mechanical Properties of Friction Stir-Welded Polypropylene Plates.

In the present study, the effects of temperature and rotational and traverse speeds on the mechanical properties of polypropylene joints that are welded by friction stir welding using a non-rotational shoulder and a heat-assisted welding process is investigated. Tensile properties, microhardness measurements, microscopy observations, and thermal analysis are carried out in the present research to evaluate the effect of the welding parameters on the mechanical properties of welded joints. The experiments are conducted and analyzed by means of a central composite design using an analysis of variance (ANOVA). Variations in pre-heating temperature from 60 °C to 80 °C, rotational speed from 800 to 1500 rpm, and traverse speed from 20 mm/min to 100 mm/min are made for observations. A remarkable joint efficiency of 94% is achieved with joints that are free of discontinuities and defects. The fractured surfaces are observed to identify ductile and brittle zones. The crystallinity is measured, and a correlation between crystallinity and joint strength is discussed. The sample with highest efficiency shows 65% crystallinity and a ratio of 37.9% of ductile zone-total fractured area.

Microstructure and mechanical properties of stainless steel 316L-Inconel 625 bimetallic structure fabricated by laser wire direct energy deposition

This study explores the laser wire direct energy deposition (LW-DED) process to manufacture bimetallic SS316L and Inconel 625 alloy. The microstructure and mechanical properties of as-printed SS316L, Inconel 625, and the bimetal were analyzed. Notably, the LW-DED bimetal exhibited superior mechanical properties and a robust metallurgical bond compared to wire arc additive manufacturing. The bimetallic interface demonstrated epitaxial grain growth, a columnar coarse grain structure, and a gradual transition with a zone thickness of 55 μm, as revealed by elemental mapping analysis. Electron backscatter diffraction (EBSD) analysis confirmed low angle grain boundaries leaning towards Inconel 625 deposition, ensuring uniform grain growth from SS316L to Inconel 625 with a consistent crystallographic direction. The EBSD analysis indicated a strong fabric texture with a <001> orientation towards the build direction. However, with increasing layer deposition, the morphology of δ-ferrite in SS316L transformed to skeletal, without interface defects and minimal laves phase. Higher layer deposition revealed the presence of laves phase, as observed in the SEM and EDAX analysis. Microhardness and nano-hardness measurements illustrated that the hardness values in the interfacial region fall between those of individual materials, showcasing a gradual transition at the interface. The tensile properties are higher in the Inconel 625, while SS 316L exhibits comparable properties to the bimetallic sample.

Synergic effect of nano sized ceramic powder of titanium dioxide and silver on AZ91D composites fabricated by friction stir processing

This study aims to observe the synergic effects of AgNPs/TiO2 on AZ91D hybrid composite fabricated via friction stir process. Nano-sized particles of titanium-di-oxide (TiO2) and silver (AgNPs) in powder form were utilized as reinforcement materials for fabricating mono and hybrid composites. The average size of the reinforcements was 80 nm. Friction stir processing (FSP) technique was done at constant parametric settings. Investigating the microstructure of the composites by optical microscope(OM) analysis showed a homogenous distribution of the incorporated particles in the AZ91D matrix. Scanning electron microscopy (SEM) analysis was done for fractography, which indicates ductile facture in all the specimens despite having any composition of reinforcements. However, rate of ductile fracture decreased with weight fraction of TiO2. Tensile strength and Micro-hardness measurements revealed enhancement in tensile properties i.e. ultimate tensile strength (UTS), yield strength(YS), percentage elongation(EL) and microhardness in all samples. The contribution of various strengthening mechanisms, i.e. Hall-patch, Orowan strengthening and thermal mismatch, were calculated for all samples and compared with actual values. Among strengthening mechanisms, Orowan strengthening is the most dominant. The modified Clyne method estimates the collective effect of various strengthening mechanisms to evaluate the theoretical YS for all samples. The maximum value of Yield strength (YS) is 175.612 MPa obtained for T-50-A-50. The maximum value for microhardness is obtained as 140.08 HV on Vickers scale for T-100-A-0 attributed to uniform dispersion of hard ceramic (TiO2) particles.

Effects of Different Austenitizing Times on the Microstructure and Properties of Cr‐Ni‐Mo‐V Series High‐Strength Steels

Herein, the effects of varying austenitizing times on the microstructure and mechanical properties of Cr‐Ni‐Mo‐V series high‐strength steel are investigated, discussing the mechanisms that enhance strength and toughness. By controlling the austenitizing duration, the microstructure during subsequent heat treatments is improved, leading to enhanced overall mechanical properties. The experimental steel undergoes treatments at different austenitizing times, and the microstructure is characterized using optical microscopy, energy‐dispersive spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction. Mechanical properties are assessed through tensile testing, impact testing, and microhardness measurements. The results indicate that, when comparing an austenitizing time of 1 to 1 h and 15 min, the ultimate tensile strength decreases by 10%, microhardness reduces by 78.2 HV, elongation increases by 1.39 times, and toughness improves by 80%. The enhancement in toughness is primarily attributed to the synergistic effect of tempered martensite and bainite within the microstructure. Fracture morphology analysis reveals that variations in austenitizing time affect carbide distribution, accelerate carbide dissolution, decrease the crack growth zone, and enhance toughness. This study provides valuable insights for designing Cr‐Ni‐Mo‐V series high‐strength steels with optimal strength‐toughness synergies.

Effects of glutathione and potassium iodide on silver diamine fluoride application on remineralisation and colour change in dentine caries of primary teeth: an in vitro study.

The aim of this study is to compare the effect of GSH (reduced glutathione) and KI (potassium iodide) on SDF (silver diamine fluoride) discolouration and dentine remineralisation. Sixteen primary molars were utilised, yielding 4 dentine specimens each. Three specimens per tooth were allocated: one as a control and the others to experimental groups. Initial microhardness measurements were taken from one remaining dentine specimen per tooth. Subsequently, all groups underwent exposure to a demineralisation solution. Colorimetry assessed specimen colour, and post-second microhardness measurements on demineralised specimens, treatments were administered as follows: group 1 (control, n = 16): 38% SDF, group 2 (n = 16): 38% SDF followed by KI, group 3 (n = 16): 38% SDF with 5% GSH added by weight. Following pH cycling across all groups, colorimetry reassessed 48 dentine specimens. Final microhardness measurements ensued, followed by statistical analysis. Normality was checked via Shapiro-Wilk, and homogeneity via Levene's test. Independent samples t test compared normally distributed groups; Mann-Whitney U compared non-normally distributed groups. ANOVA compared means of normally distributed groups, and Kruskal-Wallis for non-normally distributed ones. Repeated measures ANOVA compared dependent groups with normal distribution, and Friedman test for non-normal. Post hoc Bonferroni analyses identified significant differences. IBM SPSS 25 was used to conduct analyses. The mean ΔE* values for SDF and SDF + GSH groups were significantly higher than those of the SDF + KI group (p < 0.05). Significant differences in L* values during final colour measurement were noted between the SDF + KI group and both SDF and SDF + GSH groups (p < 0.05). Although mean remineralisation microhardness measurements were higher than mean demineralisation microhardness measurements in all groups, statistical significance was observed only in the SDF and SDF + KI groups (p < 0.05). The study found that the addition of 5% GSH by weight to SDF does not significantly affect discolouration. Moreover, the addition of 5% GSH to the SDF solution may have a minor impact on the remineralisation potential of SDF. The application of KI after SDF reduces discolouration and does not affect the expected remineralisation process.

Correlation dependences between hardening in terms of yield strength and microhardness for austenitic and ferritic-martensitic steels

Instrumental measurements of microhardness were carried out using a Vickers indenter at a constant strain rate. The yield strength values were determined for austenitic chromium-nickel steels 08Kh18N10Т, 10Kh18N9 and 08Kh16N20M2Т in the initial (non-irradiated) state, after neutron irradiation at various regimes, as well as after plastic prestrain. Similar measurements were carried out for chromium stainless steels of the ferritic-martensitic class 07Kh12NMFB and 16Kh12MVSFBR (EP-823) in the initial (non-irradiated) state and after heat treatment, leading to hardening of the material and also after neutron irradiation. The relationships between microhardness and yield strength were determined for all studied states of all steels studied. A unified correlation has been established between hardening in terms of the yield strength and hardening in terms of Vickers micro-hardness, independently of the nature of the strengthening factor and the class of steel.