Pavel Krakhmalev

Pavel Krakhmalev
Karlstads Universitet · Department of Engineering and Physics

Professor

About

87
Publications
19,718
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Introduction
Pavel Krakhmalev currently works at the Department of Engineering and Physics, Karlstads Universitet. Pavel does research in Materials Science and Engineering. Their current projects are related to (i) tribology, wear and wear prediction of heavily loaded tools and components made of high-strength and tool steels, and (ii) microstructure and properties of laser powder bed fusion stainless and tool steel, and titanium. Projects: "ATLAB - additive manufacturing laboratory at Karlstad University" (Project-ID: 20201144) by European Regional Development Fund. "Fatigue and Wear in Manufacturing Industry " (Project-ID: 20150090) KK-stiftelsen, Synergy project.

Publications

Publications (87)
Conference Paper
Electron beam powder bed fusion (PBF-EB) is a promising additive manufacturing (AM) method efficiently used for materials susceptible to thermal cracks, like high-alloy cold work tool steels. The method provides high build chamber temperature, pre-and post-heating of the build and slow cooling reducing thermal stresses during manufacturing. In this...
Chapter
Full-text available
Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel fo...
Preprint
Full-text available
Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel fo...
Conference Paper
Full-text available
Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel fo...
Article
Full-text available
The intensive cytotoxicity of pure copper is effectively kills bacteria, but it can compromise cellular behavior, so a rational balance must be found for Cu-loaded implants. In the present study, the individual and combined effect of surface composition and roughness on osteoblast cell behavior of in situ alloyed Ti6Al4V(ELI)-3 at.% Cu obtained by...
Article
Full-text available
The process of an unstable plastic flow associated with the strain rate sensitivity of mechanical properties was studied in porous 316L austenitic steel samples manufactured by laser powder bed fusion (L-PBF). Different micromechanisms of deformation and fracture of porous samples dependent on strain rate were found. It was found that despite the p...
Article
The current work considers the effect of the low Al fraction (x=0.01, 0.05, and 0.1) on the microstructure and phase composition of the CrFeCoNiAlx high-entropy alloy in-situ manufactured by powder bed fusion additive technique. The influence of a homogenization annealing at 1200 ℃ is also presented. The presence of Al powder in the pre-mixed blend...
Article
Aim of this work is to gain a comprehensive understanding of the effects of an increasing β-phase stability of Ti-alloys on the L-PBF processing behavior. For this purpose, seven different Ti-alloys with an increasing concentration of the β-phase stabilizing elements Fe and V were prepared by L-PBF and in-situ alloy formation. The Molybdenum equiva...
Chapter
Laser powder bed fusion (L-PBF) of metallic alloys results in the formation of solid metallic material with microstructure different from the conventional analogs. The differences are the result of high temperature of the molten pool, high cooling rates, steep temperature gradient, thermal cycling during manufacturing, and other factors. Since the...
Chapter
Laser powder bed fusion (L-PBF) is one of the additive manufacturing methods to produce metallic parts. The layer-by-layer manufacturing nature results in the formation of specific microstructure, achieving different properties compared to conventional analogs. In this chapter, the mechanical properties of the main classes of materials such as stee...
Article
Full-text available
In the present study, cellular lattice structures for implant applications are reported for the first-time incorporating copper directly by in-situ alloying in the laser powder bed fusion process. The aim to incorporate 3 at.% Cu into Ti6Al4V(ELI) is selected for improved antibacterial properties while maintaining appropriate mechanical properties....
Article
Full-text available
In the present study, Uddeholm Vancron SuperClean cold work tool steel was investigated concerning wear resistance and fatigue strength, using laboratory and semi-industrial tests. The Uddeholm Vancron SuperClean was designed with the help of ThermoCalc calculations to contain a high amount of a carbonitride phase, which was suggested to improve tr...
Article
Full-text available
Additive manufacturing is a good alternative to conventional methods for the production of near net shape geometries with high geometric complexity shorter lead times, being a good option for the manufacturing of dies for die casting process. In this research, a novel hot-work tool steel for aluminum die casting applications manufactured by laser p...
Conference Paper
Full-text available
The quality of the surface influences remarkably the fatigue life of additive manufactured components. This work proposes to study the influence of surface integrity on the bending fatigue life of Ti6Al4V manufactured by laser powder bed fusion. Rectangular specimens were manufactured horizontally and the last printed layer had laser track scanning...
Article
Full-text available
Biofunctionalization of Ti6Al4V alloy with metallic agents like Ag or Cu is a promising approach to add antibacterial properties and thus to reduce the risk of implant failure. This research investigates the in-situ alloying of Ti6Al4V(ELI) with 3 at.% Cu powders using Laser Powder Bed Fusion (L-PBF). The morphology and geometrical characteristics...
Article
Rock drill components operate under tough contact conditions during rock drilling. Reciprocal and unidirectional motion under high contact stresses are the common contact conditions between interconnected components. It will result in component damage and often the observed surface damage of rock drill tools is due to wear and fatigue cracks. Never...
Article
Microstructure and properties of as-built laser powder bed fusion (LPBF) steels differ from the conventional ones, and they may contain some porosity and lack of fusion. Therefore, post-treatments, including hot isostatic pressing (HIP), are used to densify the material, and tailor the properties of the final product. Usually HIP is performed as an...
Article
Topology optimization approach was used for the design of Ti6Al4V ELI lattice structures with stiffness and density close to the human bone for implant applications. Three lattice designs with volume densities of 35 %, 40 % and 45 % and corresponding elastic modulus of 18.6 GPa, 23.1 GPa 27.4 GPa close to the human bone were generated. Laser powder...
Conference Paper
In sheet metal forming, punching and blanking of advanced high performance steels, tool steels operate under severe contact conditions. It results in higher tool wear and fatigue failure, therefore, it puts high demands on the mechanical and tribological properties of the tool steels. In the present study, Vancron 40 and Vanadis 8 Extra were te...
Article
Rock drill rod failure is a big concern for the mining industry. The tough conditions required to break down rock material into small pieces subject rock drill components to high mechanical stresses and corrosion that lead to the failure of the drill rods. This paper describes a detailed examination of rock drill rods failed during field operations...
Article
The influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development was correlat...
Conference Paper
Present research is focused on an advanced stainless tool steel used for molding of corrosive plastics manufactured by laser powder bed fusion. In comparison to other tool steels, this steel possesses superior corrosion resistance and, achieves high strength via nano-precipitations of an intermetallic phase. Deeper understanding of the precipitatio...
Conference Paper
Full-text available
This article deals with the understanding of the influence of surface topography on fatigue behavior of Ti6Al4V alloy specimens produced by laser powder bed fusion (LPBF). The same laser parameters and scan strategy were used for all specimens, giving a sample density higher than 99.5 %. Two different surface topographies were obtained by using the...
Article
Full-text available
This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, c...
Article
Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tens...
Chapter
Additive Manufacturing (AM) allows to produce improved, custom made, patient specific and complex shaped medical implants. Both mechanical and biological aspects as well as type of implant and patient specific requirements determine the shape of the implant and the material it will be made of. The current chapter reviews the metals and metallic all...
Article
Laser powder bed fusion (LPBF) provides an excellent opportunity to use custom powders for complex objects without extensive machining. This opportunity is attractive for brittle and hard intermetallics, but is challenging due to cracking, anisotropy, and the formation of non-equilibrium phases. The present investigation is focused on a development...
Article
Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performe...
Article
Full-text available
The modern medical industry successfully utilizes Laser Powder Bed Fusion (LPBF) to manufacture complex custom implants. Ti6Al4V is one of the most commonly used biocompatible alloys. In surgery practice, infection at the bone–implant interface is one of the key reasons for implant failure. Therefore, advanced implants with biocompatibility and ant...
Article
This work is focused on the investigation and understanding of in situ processes in Ti-15%Mo and Ti6Al4V-1.38%Cu alloys by laser powder bed fusion (LPBF). In both materials, Mo and Cu were introduced as elemental powders into the precursor powder mixture. The effect of process parameters, i.e., energy input on surface morphology and homogeneity, wa...
Conference Paper
Powder Bed Fusion (PBF) is a manufacturing method with the advantage that it can produce objects of complex geometry. Additionally, it opens great opportunities to synthesize new materials from elemental powder using an in situ alloying approach. Potential of the in situ PBF alloying approach is nevertheless not well understood due to lack of exper...
Article
Two machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the Ti6Al4V alloys by the direct metal laser sintering. The chemical composition of powders complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for medical applications. Analysis of the oxygen and nitrogen contamination in DMLS al...
Article
Full-text available
Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc)...
Article
Full-text available
To remove residual stresses, an as-built SLM object is usually post-treated. This treatment can affect the microstructure, changing the final mechanical characteristics. This investigation is focused on the microstructural characterisation of 316L austenitic stainless steel in as-built and annealed conditions. The SLM microstructure was relatively...
Conference Paper
Full-text available
Ti6Al4V is a commonly used biomedical alloy because of its suitable mechanical and biocompatible properties. Infection at the bone-implant interface is the most probable reason for implant failure directly after implantation. Copper is a proven anti-bacterial agent and in small amounts is not toxic to the human body. Copper additions reduce the ris...
Article
Full-text available
Mechanical properties, porosity, and microstructure of Ti6Al4V (ELI) material produced by Selective Laser Melting (SLM) under controlled oxygen content were analyzed. Fully martensitic α’structure with high dislocation density and stacking faults was observed in both as-built and stress relieved samples by means of XRD and TEM. Tensile {101 ̅2} twi...
Article
In the present work, molecular dynamics simulations were used to investigate the impact of the tool microstructure on the wear behavior of ferrite workpiece during nanoscratching. The tool microstructure was modified by varying the carbide (cementite) contents. The simulation results show that dislocations are the primary mechanism for plastic defo...
Article
Full-text available
Direct metal laser sintering (DMLS) is an additive manufacturing technology used to melt metal powder by high laser power to produce customised parts, light-weight structures, or other complex objects. During DMLS, powder is melted and solidified track-by-track and layer-by-layer; thus, building direction can influence the mechanical properties of...
Article
Direct metal laser sintering (DMLS) is a relatively new technology that is developing rapidly. Since DMLS material is created by melting/solidifying tracks and layers from powder, even building geometry can influence the mechanical properties. To certify a material, the testing specimens must be designed and manufactured according to the appropriat...
Conference Paper
Full-text available
In dry sliding surfaces, one of the central phenomena during mechanical contact is the material transfer and accumulation between the surfaces, called galling failure. For example, in sheet metal forming process, galling is the major cause of reducing life of both tool and formed sheet. Galling is an inherently multiscale processes. In laboratory s...
Article
The adhesive properties of Fe(110)/Fe(110) and Fe3C(001)/Fe(110) countersurfaces have been investigated by using classical molecular dynamics simulations. The simulation results show that Fe3C/Fe exhibits a relatively lower adhesion compared to the Fe/Fe. Additionally, the temperature dependence of the adhesive properties between 300–700 K has been...
Conference Paper
Full-text available
Direct metal laser sintering is an additive manufacturing technology where powder is melted/solidified by laser beam layer-by layer to produce complex components. Due to the fast heating/cooling during the process, the DMLS microstructure differs from cast/wrought Ti6Al4V alloy. Track-by-track, layer-by layer DMLS method also has an effect on mecha...
Conference Paper
Full-text available
In sheet metal forming processes, the accumulation and transfer of sheet material to tool materials, galling failure, is major cause of reducing tool life and formed sheet as well. It is assumed that galling initiates as local adhesive wear between two surfaces, therefore in order to improve galling resistance of a material by reducing the adhesion...
Article
Full-text available
The article explores an evolution of a microstructure in AISI 420 martensitic stainless steel during selective laser melting. Several upper layers had hardness of 750. HV and contained 21. ±. 12 vol.% austenite phase. The final bulk microstructure consisted of thermally decomposed martensite with hardness of 500-550. HV and unusually high, 57. ±. 8...
Article
Full-text available
Friction is a fundamental phenomenon in tribology involving complex mechanisms between the contacting surfaces. Measurements of friction are often made using devices with substantially larger contact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials, influence of particular microstruct...
Article
Full-text available
We have studied the mechanical behavior of multi-walled carbon nanotubes for bending strains beyond the onset for rippling and buckling. We found a characteristic drop in the bending stiffness at the rippling and buckling onset and the relative retained stiffness was dependent on the nanotube dimensions and crystallinity. Thin tubes are more prone...
Article
An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights in...
Article
Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research,...
Article
free access until 31st January, 2014 http://www.sciencedirect.com/science/article/pii/S0925838813020689 Selective laser melting (SLM) is a kind of additive manufacturing where parts are made directly from 3D CAD data layer-by-layer from powder material. SLM products are used in various industries including aerospace, automotive, electronic, chemic...
Article
free access until 31st January, 2014 http://www.sciencedirect.com/science/article/pii/S0925838813020689 Selective laser melting (SLM) is a kind of additive manufacturing where parts are made directly from 3D CAD data layer-by-layer from powder material. SLM products are used in various industries including aerospace, automotive, electronic, chemic...
Article
Full-text available
We present a detailed experimental study of the onset of rippling in highly crystalline carbon nanotubes. Modeling has shown that there should be a material constant, called the critical length, describing the dependence of the critical strain on the nanotube outer radius. Surprisingly, we have found very large variations, by a factor of three, in...
Article
One of the major causes of tool failure in sheet metal forming is wear in the form of galling. Galling is gradual buildup of adhered sheet material on the tool and leads to unacceptable scratches on the sheet surface and to components that fail to meet tolerances. Because it is difficult to reproduce operational and interactional conditions in labo...
Article
Process parameters of selective laser melting affect the response of a powder–substrate system and, therefore, the geometry and microstructure of the manufactured parts. The experiments were carried out at fixed values of laser power (50 W), spot diameter (70 μm) and powder layer thickness (80 μm). In this research, influence of the energy input pa...
Article
EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were high...
Article
Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder...
Conference Paper
The increasing need to produce complex shapes has raised the interest of tool manufacturers to investigate suitable tool geometries along with suitable tool and sheet material combinations. Punching and blanking are the most frequently used processes in sheet metal forming. Chipping of punches is a major challenge in punching of stainless steel all...
Article
We present a detailed analysis of the image formation mechanisms that are involved in the imaging of carbon nanotubes with scanning electron microscopy (SEM). We show how SEM images can be modelled by accounting for surface enhancement effects together with the absorption coefficient for secondary electrons, and the electron-probe shape. Images can...
Article
Tool damage in sheet metal forming of stainless steel is of high concern for the forming industry. In the present work, ingot cast AISI D2 and advanced powder metallurgy tool steel (PM) cold-work tool steels were evaluated and ranked regarding wear mechanisms and galling resistance. Wear tests were performed using a slider-on-flat-surface (SOFS) tr...
Article
Full-text available
We report measurements of the bending stiffness in free standing carbon nanotubes, using atomic force microscopy inside a scanning electron microscope. Two regimes with different bending stiffness were observed, indicative of a rippling deformation at high curvatures. The observed critical strains for rippling were in the order of a few percent and...
Article
IntroductionMaterials and Method Results and DiscussionConclusions AcknowledgmentsReferences
Article
In the present study, the influence of nickel content on the machinability of a prehardened hot-work tool steel was investigated. The machinability with varying nickel content from 1 to 5wt.% was characterized in end milling and drilling by evaluating tool life, cutting forces, and tool/chip interface temperature.Nickel content showed to have a pos...
Article
Surface residual stress, microstrain and domain size were determined using X-ray diffraction in shot-peened low-alloyed and hot-work tool steels subjected to varying temperatures (200–600°C) and times (0.5–50h). The stress relaxation was directly related to microstrain decrease and domain size increase.The Zener–Wert–Avrami function was used to mod...
Article
In many metal forming operations, frictional heating occurs at the interface due to a sliding contact. Generally, the controlling wear mechanism in the tribological system is attributed to adhesive wear. Understanding of the influence of temperature on wear mechanisms is needed for the development of materials and for optimization of the forming pr...