Surface Hardening Methods Research Articles

STRENGTHENING OF THE SURFACE BY FRICTION

The study is devoted to the application of the method of surface hardening by friction Object of study - the process of surface hardening by friction.Subject of study - samples of 65G steel the method allows achieving high values of hardness, strength and wear resistance of materials in a short time and at much lower cost compared to other processing methods. The aim and objectives of the study are to investigate the nature of surface hardening of steel samples by friction. To achieve this goal, the following tasks are envisaged: manufacturing samples from 65G steel in the form of plates, preliminary heat treatment of samples for their maximum thermal hardening, hardening of the surface of samples by friction, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness and depth of hardening of these samples, conclusions on the influence of processing factors on the hardening result. Based on the experimental data obtained, we constructed graphs of microhardness changes in the cross-section of the samples and studied the microstructures. It can be seen that after friction treatment, a layer with a modified structure is formed in the surface of the samples. The microhardness of the surface is significantly higher (approximately 2 times) than the microhardness of the main part in the samples. Metallographic analysis has shown that the layer formed in the samples has a martensitic structure characterized by a higher degree of dispersion and microhardness compared to the martensitic structure obtained during the previous heat treatment. Changes in the microstructure and microhardness of the samples that were surface hardened using different processing modes were compared. Certain differences in the characteristics of their hardened «white» layers were found. It is also shown that the hardened «white» layer is located along the entire length of the surface in the samples and is continuous and homogeneous.

Nitrogen diffusion along the layer boundaries after nitriding of multilayer materials

Diffusion processes play a key role in formation of the structures of new materials and technological processes of strengthening heat treatments, since diffusion is the reason for redistribution of substances in solids. An urgent task is to develop technologically advanced and effective methods for strengthening materials in order to improve their performance properties. There is an increasing need to improve chemical heat treatment methods, which directly affects the wear resistance of working surfaces, and, consequently, the product service life. Near-surface volumes experience increased loads, so the formation of high-strength layers becomes an important task. Quite a few methods of surface hardening are known, among which carburization, nitriding, nitrocarburization and others are widely used. The most interesting is nitriding, since it increases hardness, strength, fatigue limit, and heat resistance. However, despite the proper advantages, nitriding has a number of disadvantages, including the holding duration and small thickness of diffusion layers. The solution is related to intensification of the technological process by increasing the nitriding temperature, activating the nitriding media or directly the parts surface. All these solutions are aimed at accelerating diffusion processes, both in grain volume and along grain boundaries, the velocity along which is many times higher than the velocity of volumetric diffusion. It may be effective to use a new type of structural metal materials with a multilayer structure of hundreds of layers, with thicknesses in the micron and submicron ranges separated by large angular boundaries. The results of metallographic studies showed the effect of the steel layers interchange in the multilayer metal material on diffusion depth after chemical heat treatment. The authors proposed an accelerate diffusion model of diffusible element along the layer boundaries.

Increasing of the service life of massive tools using combined restoration and hardening technologies

Combined methods for restoring and strengthening of massive metal and soil-working tools are considered, which simultaneously provide induction quenching or surfacing and plasma surface treatment. These methods increase not only the hardness and wear resistance, but also the impact strength and crack resistance of the tool, which is not provided by traditional methods of surface hardening. Keywords:tool, tool steel, surface, induction quenching, plasma jet, surfacing, structure, crack resistance zaplazmu@yandex.ru

Electron beam hardening of nanobainitic steel

Nanobainitic steels with high Si content are very promising materials due to the very favourable combination of mechanical and functional properties. However, sometimes in order to achieve the required results, it is necessary to further increase the surface's layer hardness. One of the feasible methods of surface hardening is electron beam hardening. In this work, 30 × 20 × 150 mm blocks made of nanobainitic steel were hardened using a defocused oscillating electron beam. Two methods of surface hardening were used – with movement of the sample relative to the heat source and hardening using only beam oscillation. The obtained samples were then subjected to light microscopic and scanning electron microscopic microstructure analysis as well as Vickers hardness testing. The average hardnesses of all hardened samples were in the range of 641–681 HV0.1 which means the surface hardening resulted in a hardness increase in the range of 239–279 HV0.1. The occurrence of similar hardening depths and hardness values in specimens hardened by both methods was an interesting phenomenon that was observed. The amount of energy input needed to achieve similar results was up to 35% less for the method without specimen movement.

Improving surface hardness of AISI 1045 steels using melamine derived from urea

ABSTRACT AISI 1045 steels are medium carbon steels used in applications that require greater strength and hardness such as gears, railway wheels and tracks, crankshafts, rolls, axles and other structural components. Although AISI 1045 steels are highly demanded engineering materials, they suffer from deformation and wear resistance when these applications are used. The hardness and wear resistance of the material are improved using a surface hardening method. Pack nitriding is the cheapest and easiest method of surface hardening method implemented in this work. The surface hardness of AISI 1045 steel is improved by the diffusion of nitrogen from the nitrogen-bearing material (melamine) to the surface of the steel and forms a metal nitride compound, which has strong hardness and wear resistance. This work reports that substantial surface hardening of AISI 1045 steel was achieved by the pack nitriding method using melamine obtained by in situ reaction of urea. The surface hardness increases manifold with the amount of melamine used, soaking time and temperature. The microscopic investigations of the nitrided surfaces of the metal show the formation of two distinct layers. The microstructural properties and hardness of the samples before and after nitriding were thoroughly investigated and interpreted.

Laser hardening of steel with a 120 kW laser at high throughput

Lasers can be used as a possible method for steel surface hardening. This process involves a laser acting as a heat source and the sample itself as a heat sink for the required rapid cooling. Typically, spot sizes are in the millimeter range and laser powers are in the kilowatt range. The emergence of commercial fiber lasers in the 100-kW class enables higher throughput levels. We demonstrate an increase in hardness from 160 HV100 to 600 HV100 of 1.7225 / 42CrMo4 / AISI 4140 steel with 10 ms pulses at 120-kW peak power (spot diameter = 38 mm) and a feed rate of 95 mm/s. A width of increased hardness of over 26 mm was achieved, along with a 10 mm wide stripe of uniform hardness. The hardness was increased within a depth of 0.9 mm being homogeneous down to 0.6 mm. Further improvements may be achieved through advanced beam shaping and enhanced scanning parameters.

Surface hardening of structural steels ShKh15 and 40KhN2MA by pulsed plasma flows

The article is devoted to an innovative method of surface hardening of steels 40KhN2МА and ShKh15 by pulsed plasma flows. The treatment was carried out in a wide range of absorbed energy density from 20 to 100 J/cm2, with a plasma exposure duration of 1 ms. The results of a study of the structure, phase composition and morphology of the modified surface layer, as well as such characteristics as thickness, microhardness, surface roughness, and level of residual stresses are presented. The modified layer of steel contains several structural components with distinctive characteristics. The maximum thickness of the modified hardened layer was 125 µm. The conducted research made it possible to establish optimal treatment modes, characterized by an increase in surface microhardness by 3—4 times, a decrease in roughness by up to 35 % and the presence of compressive residual stresses, which opens up prospects for the development of highly effective technology for strengthening critical products.

Analysis of the influence of electrospark alloying parameters on the structural state of alloyed surfaces

Рroblem. Among the promising methods of surface hardening and modification are techniques based on the treatment of metals and alloys with high-energy flows of materials and energy. Among the modern methods of metal surface treatment is electrospark alloying (ESA), which allows obtaining surface structures with unique physical, mechanical and tribological characteristics. It is known that alitization provides metal surface layers with protection against corrosion and oxidation at elevated temperatures. The traditional method of forming alitized coatings is chemical-thermal treatment. The paper proposes a method of alitization by ESA. Many parameters influence the formation of the layer during alitization by the ESA method. First of all, it is the energy parameters. Goal. The aim of the work is to evaluate the effect of the ESA alloying process performance on the structure formation. Methodology. The study was carried out on samples of steel 20. An aluminium electrode in the form of a wire was used as a tool electrode for ESA. Different alloying modes were investigated, the discharge energy and performance were changed. The alloying was carried out in two stages. At the first stage, the aluminium electrode was used at classical performance values. At the second stage, the capacity was reduced by two and four times. At the second stage, a saturating paste containing aluminium powder was applied to the surface before the ESA. The microstructure of the obtained modified surfaces was examined under an optical microscope, the surface roughness and microhardness distribution in the surface layer were determined. Results. The use of two-stage alitization increases the microhardness of the hardened layer and the diffusion zone, as well as reduces the surface roughness. The coating integrity was 100%. (originality) A new method of alitisation based on ESA is proposed, which allows to obtain 100% continuity with high adhesion to the substrate. Рractical value. For practical implementation, it is recommended to perform alitization according to the following variant: the first stage is ESA with an aluminium electrode with a discharge energy Wp = 4.6-6.8 J, the second stage is the application of a saturation paste containing aluminium powder and graphite powder. Electrospark alloying should be carried out with a reduced productivity by about two times.

Abrasive Wear Resistance and Tribological Characteristics of Pulsed Hard Anodized Layers on Aluminum Alloy 1011 in Tribocontact with Steel and Ceramics in Various Lubricants

Based on the analysis of known methods of surface hardening of aluminum alloys (chromium plating, plasma electrolytic oxidation, hard anodizing), the prospects for pulsed hard anodizing are shown both for improving the functional characteristics of alloys and for large-scale implementation of this method. The purpose of this work is to show the possibility of pulsed hard anodizing to improve the serviceability of low-strength aluminum alloy 1011 under conditions of abrasive and sliding wear. The influence of the pulsed anodizing temperature on the phase-structural state of the synthesized layers, their abrasive wear resistance, and tribological characteristics in various lubricants were established, and the mechanism of wear of these layers was proposed. It is shown that with an increase in the temperature of pulsed anodizing, the wear resistance of the synthesized layers increases, and their abrasive wear resistance decreases. The negative effect of lubricating media on the wear resistance of the synthesized layers compared to tests under dry conditions was shown, and an explanation for this phenomenon is proposed. A significant (up to 40 times) increase in wear resistance in dry friction of anodized low-strength aluminum alloy 1011 compared to high-strength aluminum alloy 1050 was shown.

Innovative technologies for strengthening of internal surfaces of suspension parts of heavy-loaded machines by laser and high-frequency induction methods

In the article innovative methods of surface hardening of internal surfaces of machine parts by laser and highfrequency induction heating are presented. The relevance of applying the methods of laser and induction hardening for the internal surfaces of heavily loaded parts of quarry equipment is proved. The results of modeling and calculation of thermal and electromagnetic fields under the influence of an external electromagnetic field and laser radiation beams are presented. The original design of a complex of equipment for processing the internal surfaces of suspension parts by external electromagnetic field is described. The optimal designs of inductors with magnetic circuits made of various materials are shown. The study of the structure and properties obtained on the internal surfaces of heavily loaded suspension parts of cars, line of the BelAZ company, treated according to the optimal modes of surface induction exposure is given. The developed original technology and equipment of laser surface hardening, which makes it possible to increase the wear resistance of heavily loaded parts, is described. Data on the implementation of research results at JSC “BELAZ” – the Management Company of the Holding “BELAZ-HOLDING” for processing a wide range of heavily loaded suspension parts are given.

Wear properties of borided WC-Co

Abstract Today, artificially produced tungsten carbide (WC) tools are used as an alternative to diamonds such as mining, drilling, cutting, or machining. Although it is called WC, it also contains a certain amount of cobalt (Co). The most important reason for this is that it increases the wear resistance of the WC. Boriding is a type of surface hardening method that provides wear, hardness, and corrosion resistance to the applied surface. In boriding, which is a kind of diffusion process, there is no change in the dimensions of the materials since the boride layer grows from the outer surface of the materials to the inside. In this study, the development of surface properties by boriding of 90 wt% WC and 10 wt% Co-containing abrasive bits used for drilling were investigated. The samples were borided in an atmosphere-controlled furnace at 1173, 1273, and 1373 K for 1, 2, and 3 h by the pack boriding method. After the boriding processes, the microstructure, hardness, and chemical composition of the boride layers formed on the surface of the samples were examined, and finally, the wear tests were carried out to reveal the differences compared to the unborided sample.

Surface hardening of TiZrNbHfTa high entropy alloy via oxidation

We investigate the oxidation of TiZrNbHfTa high entropy alloy between 550 °C and 650 °C as a surface hardening method. Coarse-grained specimens with grain boundaries perpendicular to the surface exhibit catastrophic oxidation, while ultrafine-grained, cold-rolled specimens show a continuous mass gain and the formation of an adherent, µm-sized, vitreous oxide layer. Underneath, TiZrNbHfTa decomposes into a bcc- and an hcp-phase, while selective internal oxidation of hafnium and zirconium occurs upon oxygen inward diffusion. Oxygen concentration- and microhardness-depth profiles confirm an increase in oxygen concentration and hardness at the surface, raising the initial hardness by four times to 1522 ± 64 HV0.5.

Applying Thermo-Reactive Diffusion Method to Surface Coating of H13 Tool Steel Using Ferrovanadium, Ferrochromium, and Misch Metal

The thermo-reactive diffusion (TRD) process is a method for surface hardening that improves the hardness, corrosion resistance, and wear resistance of the materials. In this study, the effect of composition was investigated, by using 8, 12, 16, 20, and 24 wt% of ferrochrome and ferrovanadium with equal amounts, along with 3 wt% aluminum and borax. The TRD process was carried out at 1000°C for 7 hours on AISI H13 hot work tool steel so that a complex coating of chromium-vanadium carbide was formed on the H13 substrate. Optical and scanning electron microscopes were used to evaluate the thickness and microstructure of the samples, respectively. Moreover, the amount of alloying elements and constituent phases on the surface were analyzed by point analysis and X-ray diffraction. The micro-hardness method was used to evaluate the hardness of the samples. The results of this study showed that by increasing the amount of ferroalloy, the hardness and thickness of the coating increase. The optimal composition with 8% ferrochrome and 8% ferrovanadium was found to yield a coating with a thickness of 7.65 μm and a hardness of 2115 HV.

Kinetic and mechanical properties of boronized AISI 1020 steel with Baybora-2 powder

In this study, package boronizing process was applied to AISI 1020 steel by using Baybora-2 boronizing agent and the kinetics of boronizing process was investigated. The pack boronizing process was performed at 1223 and 1323 K temperatures for 2, 4 and 6 h. The properties of the boride layer formed on the surface as a result of the boronizing process were determined using optical microscopy and SEM analysis. XRD analysis was performed to determine the phases formed in the boride layer. As a result of the analysis, it was determined that the boride layer consisted of FeB and Fe2B phases. It was determined that the thickness of the boride layer increased with the increase of boronizing time and temperature. While the boride layer thickness for the temperature of 1223 K was between 115 and 196.3 μm, the boride layer thickness for the temperature of 1323 K was found to be between 157.2 and 304.7 μm. In this study, a boriding powder, patented and under development, was used and a surface layer with a hardness of 2224 HV was obtained on the surface of AISI 1020 steel. This hardness value is approximately 5 times the hardness values of steels hardened by traditional surface hardening methods such as cementation and nitriding. Also, considering the boride layer thicknesses, the activation energy was calculated as 162.26 kJ/mol using the classical kinetic method.

Effect of pack carburizing and viscosity of quenching media on AISI 1010 steel

Pack carburizing is a method of surface hardening of steel which is carried out by diffusing carbon into the material where the carbon is initially solid. This study aims to determine the effect of pack carburizing treatment on the microstructure and hardness of AISI 1010 steel. The material was then cooled slowly in the oven to a temperatur of 150oC which was then followed by air cooling. Single Quenching is then carried out by reheating the carburizing material to a temperature of 870oC and then holding it at that temperature for 60 minutes. Quenching is done by cooling the material quickly using a cooling medium of varying viscosity. The results of the composition test showed an increase in carbon content to 4.1159%. The results of microstructure observations showed that a massive pearlite structure was formed to a depth of ± 0.794 mm on the surface of the carburizing specimen. The results of the hardness test using the Vickers method showed that the hardness value of the raw material increased after carburizing to 217.88±5.13 HV due to the formation of a pearlite structure. With this increase in hardness, the application of AISI 1010 Steel material becomes wider.
 Keywords: Carburizing, Quenching, Viscosity, Hardness, Microstructure

Structure and Properties of Al-Co-Cr-Fe-Ni High-Entropy Alloy Subjected to Electron–Ion Plasma Treatment

High-entropy alloys (HEAs) are a new class of materials consisting of at least five elements in equiatomic or near-equiatomic ratio. HEAs are subjected to various types of surface treatment to improve their properties. One of the most promising methods of surface hardening is electron beam processing. This study aims to examine the structure, elemental, and phase composition of the AlCrFeCoNi HEA surface layer after the deposition of a (B + Cr) film and irradiation with a pulsed electron beam. HEA samples of non-equiatomic composition (33.4 Al; 8.3 Cr; 17.1 Fe; 5.4 Co; 35.7 Ni, at. %), fabricated by wire-arc additive manufacturing (WAAM), were used as study objects. Modification of the HEA surface layer was carried out by a complex method combining deposition of (B + Cr) film samples on the surface and irradiation with a pulsed electron beam in an argon medium. The mode of modification was identified. It makes it possible to increase microhardness (almost two times) and wear resistance (more than five times), reduce the friction coefficient of the HEA surface layer by 1.3 times due to the decrease in the average grain size, formation of particles of borides and oxyborides of complex elemental composition, the introduction of boron atoms into the crystal lattice of HEA.

Development of a technology for manufacturing of lightweight stamped ball plugs with surface hardening

The decrease in the mass of bulb stoppers during their manufacture by stamping is experimentally studied. A new design of a bulb stopper from two pipe billets with an internal location of the joint, a technology for its manufacture and methods of surface hardening are proposed. Keywords: valve, bulb stopper, stamping, crimping, surface hardening. vasilijlobov99130gmail.com, remshev@mail.ru, katerinafrolova1996@mail.ru

Coatings from high-entropy alloys: State and prospects

The authors made a brief review of recent publications by foreign and domestic researchers on the structure, phase composition, and properties of films and coatings of five-component high-entropy alloys (HEA) on various substrates and modification of the HEA surface by various types of processing. The main methods of applying films and coatings are considered: magnetron sputtering, thermal sputtering, laser sputtering, and electrodeposition. Particular attention is paid to the deposition of coatings on stainless steels and titanium alloys. The positive change in the tribological, strength properties, and corrosion resistance of film coatings in a wide temperature range is analyzed and possible causes of the observed effects are discussed. The role of solid solution strengthening, formation of fine-grained structure, and the formation of oxide layers enriched with one of the HEA components were taken into account. The authors identified new methods for applying coatings from HEA and subsequent processing. Using Nb and Ti doping as an example, their role in increasing microhardness, wear resistance, and reducing the friction coefficient in coatings were revealed. Electrolytic polishing, electroerosive machining, mechanical polishing and their combination are considered among the methods of HEA surface treatment. A number of works propose a method of powder borating to increase the surface strength and wear resistance of HEAs. The paper considers analysis of works on electron-beam processing as one of the promising and high efficient methods of HEA surface hardening.

SELECTIVE SURFACE HARDENING OF GEAR MECHANISM SHAFT BY ROBOTIC LASER 3D SYSTEM

A robot-based laser 3D hardening method is proposed as a finishing operation to increase the wear resistance of the metal end-products. The laser hardening process of the surface layer of the products by changing its structure is one of the most effective methods of selective surface hardening. Thermal hardening of metals and alloys by laser radiation is based on local heating of a surface area under the influence of radiation and subsequent cooling of this surface area at a supercritical speed due to heat removal into the inner layers of the metal. The used robot-based laser 3D system (FANUC industrial robot and SCANLAB scanning optics) allows processing the surfaces of any complexity and geometry, including the shafts of the gear mechanism of the seed drill. It was found that the development and improvement of the technological process of manufacturing steel shafts of the gearbox of the seed drill is an urgent technological problem due to the rapid retirement of the shaft, which leads to the expenditure of time and money for its replacement. The most heavily loaded sections of the shaft were pre-estimated using the SolidWorks Simulation software package. A high-power TruDisk 8002 solid-state disk laser with a maximum laser power of 8 kW and a wavelength of laser radiation of 1030 nm is used for high-quality laser surface treatment of the AISI 1066 steel shaft of the gear mechanism. The laser surface heat treatment was carried out using a constant power strategy (continuous mode), varying the laser power in the range of 1.35–2.25 kW. Based on the Fe-Mn two-component state diagram, the critical points of the temperature of complete austenization of the studied steel were previously predicted taking into account the chemical composition of the material. Additionally, the energy density values of the laser beam with a diameter of 1 mm on the working surface was estimated. The results showed that the surface hardness of the shaft was about 2.5 times higher compared to the untreated surface. The working ranges of laser heat treatment parameters of the gearbox shaft were established to increase the hardening intensity (100–150%) of the responsible areas.

THE CHROMIUM AND MANGANESE DISTRIBUTION IN THE DIFFUSION LAYER OF STEEL 35CrNi2-3 DURING THERMОDIFFUSION SATURATION

Increasing the strength, hardness and wear resistance of the material of machine parts and mechanisms has been an urgent task for many decades. The most promising option of its solution is surface hardening. Among the wide variety of surface hardening methods (heat treatment, deformation methods, etc.), in recent time, much attention has been paid to the chemical-thermal treatment methods, which consist in saturating the metal surface with one or more elements. The article describes the features of thermal diffusion saturation of steel 35CrNi2-3 with chromium and manganese at a temperature of 1000°C. A technique for analyzing the obtained coating is presented, based on the possibilities of X-ray spectral microanalysis of the diffusion layer on transverse microsections of the obtained samples. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460 LV universal scanning (scanning) electron microscope. The results obtained show that the joint diffusion saturation of the surface of steel 35CrNi2-3 with manganese and chromium leads to the formation of an external diffusion layer on the metal surface, consisting of a solid solution of Cr‒Fe‒Mn substitution with a gradient in composition. The average diffusion coefficients of chromium and manganese in the α-phase of chromium were DCr = 3,5·10‒15 m2/s and DMn = 5,14·10‒14 m2/s, respectively; in the γ-phase of iron ‒ DCr == 1,16·10‒17 m2/s and DMn = 1,43·10‒17 m2/s, respectively. The depth of the diffusion layer of chromium in the metal at joint saturation with manganese was 30 μm, the diffusion layer of manganese was 37 μm. The large depth of penetration of manganese into steel is explained by its lower work function of electrons and the contribution of electromigration of manganese ions to diffusion.