Surface Hardening Treatment Research Articles

Effects of surface hardening by laser shock peening and shot peening on a nickel-based single-crystal superalloy CMSX-4

Improving the expected life of nickel-based single-crystal superalloy turbine components by surface hardening treatments including laser shock peening (LSP) and mechanical shot peening (MSP) are of particular interest for mitigation of life limiting damage such as environmental assisted cracking in hot section components of gas turbines. In the present study the effects of LSP and MSP on the surface roughness, microhardness and work hardening of a nickel-based single crystal superalloy CMSX-4® have been assessed. Surface roughness was measured using laser profilometry. The degree of work hardening was measured using electron backscattered diffraction with local misorientation analysis. The analysis showed evidence for a work hardening layer in the MSP sample to a depth of approximately 70 μm. Sets of slip bands extending far into the bulk of the sample were observed in the LSP-treated sample, without any evidence of a work hardening layer. Microhardness measurements used to gauge the depth of residual stress showed that LSP produced a much deeper hardness profile than MSP, with compressive residual stress depths of 1000 μm and 200 μm in LSP and MSP respectively. The retention of hardness after a heat treatment of 50 h at 700 °C was more prominent in the LSP sample than in the MSP sample. LSP and MSP have therefore been shown to be at the opposite ends of the spectrum of surface hardening treatments of CMSX-4, with LSP giving milder hardening, but to a greater depth.

Improved tribological behaviour of super duplex stainless steel through plasma nitriding at ultra-low temperature without prior polishing

Super duplex stainless steels (SDSS), widely used in industries such as offshore oil and gas, offer a unique combination of high strength and corrosion resistance. However, surface hardening treatments are crucial to enhance their performance and extend service life. This work investigates the effect of plasma nitriding on the tribological behaviour of SDSS SAF 2507. Samples are treated without prior polishing (as received, AR) at ultra-low temperatures (250 and 300 °C) aiming to avoid detrimental CrN precipitation. Comprehensive microstructural characterization, corrosion studies, and tribological tests (scratch and ball-on-disc) are conducted on samples that do not present CrN (PN). Results indicate that the hardness of PN samples nearly doubles that of AR samples due to the presence of expanded austenite. Corrosion tests show improvements in passivity for PN samples. In scratch tests, while the AR material undergoes progressive plastic deformation, in PN material the nitrided layer breaks down only after reaching a critical load. In ball-on-disc test, wear rates are remarkably lower for PN condition compared to AR condition. Wear mechanism is tribo-oxidative and abrasive for the AR condition. Wear of PN samples is characterized by asperity break-off and ratcheting. The nitrided layer in PN samples exhibits an enhanced load-bearing capacity that improves wear resistance in both tests.

Content and Dispersion of Ferroalloys in the Coating During Microarc Alloying of Steel

Introduction. The main disadvantage of traditional processes of diffusion surface hardening of steel products is its long duration. Therefore, the problem of intensification of such processes is relevant. To solve it, the use of high-energy effects on the material is proposed, which allows us to obtain a hardened surface layer from a coating composed of ferroalloy powders containing alloying elements. There is no data in the literature on the required content and dispersion of such powders in the composition of the coating. The aim of this study was to select the particle size of ferroalloys and their concentration in the coating to achieve the most effective hardening of the processed product.Materials and Methods. For experimental studies, cylindrical samples made of steel 20 with a diameter of 12 mm and a length of 35 mm were used. On the surface of these samples, an alloying coating containing ferroalloy powders and an electrically conductive gel as a binder was applied. After that, the samples were immersed vertically for half their length into a metal container, which was then filled with carbon powder with a particle size of 0.4–0.6 mm. Then an electric current of 2.5 to 3.0 A was passed in the circuit power source — container — carbon powder — sample. The duration of the process was 2–8 minutes.Results. The calculated estimation of the electrical conductivity of coal powder was performed, and the thermophysical parameters of microarc heating of steel were calculated. These include the power released by electric current on the surface of the steel product, the density of the heat flux, and the energy of a single microarc discharge. The expressions for calculating the particle size of ferroalloy powder were obtained, as well as the experimental dependencies of the diffusion layer thickness on the particle size of ferroalloys and their content in the coating.Discussion and Conclusion. The results of this study have allowed us to determine the size range of ferroalloys and their content in the coating. This information is essential for optimizing the alloying process and ensuring the most efficient surface hardening treatment for steel products. The data collected will be used to develop improved technological processes for the surface hardening process, leading to improved product quality and performance.

INVESTIGATION OF CRYOGENIC TREATED DRILL BIT

We look into brief introduction of cryogenic treatment. Our focus throughout the report is more on cryogenic treatment of tool steel and high speed steel. In metal forming industry tools are exposed to very complex and rough surface conditions, which are the result of different effects (mechanical, thermal and chemical) and thus require well defined mechanical properties. Different approaches are followed to increase the surface properties of tool steels. The surface hardening treatments of steel has shown significant improvement of various properties including wear and fatigue resistance. Cryogenic treatment is yet another approach acknowledged by some to extend the tool life of many cutting tools. We will describe the complete procedure and investigate the effects on the metallurgical changes in the tool steel. However real mechanisms behind the better performance of tools are still in doubt. Studies in the given references on cryogenically treated tool steel shows micro structural changes in material that can influence the tool life. However little is gained from the experimental results showing involvement of carbide precipitations. Cryogenic treatments of carbides has yet to be extensively studied. In this paper drill bits are treated with cryogenic method and to predict the hardness, wear strength and other results are analysing.

Monitoring of numerical simulation of the process of surface hardening treatment of titanium alloys

The paper presents the results of monitoring numerical simulation of the process of surface hardening of titanium alloys VT20 and OT4 by electric spark alloying, which can be used in the design of technological processes for the manufacture of titanium blades of steam turbines. Visualization of the resulting model, carried out using the MatLab computer program, gives a visual representation of the process under study. A good agreement of experimental and calculated (simulated) data allows you to set the parameters of the technological processes of hardening of turbine blades according to the simulation data.

Effect of ultrasonic-assisted surface plastic deformation on the microstructures and tensile properties of discrete laser hardening treated Cr–Ni–Mo alloyed steel

Discrete laser surface hardening (DLSH) can form an array of separate high hardness zones with excellent wear resistance on the surface of ferroalloys. However, the soft self-tempering zone at the subsurface layer with slow thermal diffusion seems to be unavoidable and harmful to the workpiece. In this study, the microstructure evolution and tensile properties of martensitic Cr–Ni–Mo alloyed steel after discrete laser surface hardening (DLSH) and further combined ultrasonic-assisted surface plastic deformation (USPD) treatment were investigated by the X-ray diffraction (XRD), electron back-scattered diffraction (EBSD), transmission electron microscope (TEM) and electronic universal testing machine. Results show that the combination of USPD treatment changed the phase, dislocation density, amount of twins, and texture component in the DLSH treated surface layer and caused a difference in the strengthening mechanism between laser hardened zone (HZ) and substrate zone (SZ). Because tensile cracks tend to initiate first in the subsurface soft zone outside HZ, the tensile strength and yield strength decreased by 10.4% and 4.7% after DLSH treatment. After USPD treatment, the surface gradient plastic deformation improved the subsurface strength of soft zone, and the threshold value of crack initiation increased accordingly. Finally, the effective inhibition of crack initiation at the surface layer caused a stable back stress hardening effect, and significantly increased the yield strength and tensile strength of the material by 5.1% and 3.7%, respectively, compared with the untreated sample. The DLSH and USPD treatment decreased the continuous deformation ability of the sample surface, and the fracture surface showed a brittle fracture.

Local oxynitriding of AZ31 magnesium alloy by atmospheric-pressure plasma treatment at room temperature

A surface-hardening treatment for AZ31 magnesium alloy using an atmospheric-pressure plasma jet (APPJ) at room temperature was developed. Magnesium is a potential engineering material because it is lightweight; however, magnesium alloys are difficult to heat-treat because of their low flaming temperature. Magnesium alloy specimens were irradiated with a localized atmospheric-pressure plasma jet generated by dielectric-barrier discharge for 180 s in air. The APPJ excited oxygen and nitrogen molecules in the ambient air, resulting in the formation of an oxynitrided layer; oxygen and nitrogen diffusion layer, on the surface of the magnesium alloy. The hardness and elemental distribution for the treated surface were examined. The top surface of the APPJ-treated magnesium alloy achieved a maximum hardness of 108 HV, which was ∼1.7 times greater than that of the untreated surface. Elemental analysis using an electron-probe microanalyzer revealed strong oxygen and nitrogen signals corresponding to the hardened region of the magnesium alloy, meaning that the hardness increased as a result of the formation of the oxynitrided layer. The proposed APPJ treatment is a promising approach for locally hardening magnesium alloys without using a heat treatment.

Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*

Abstract Stainless steels are commonly used for high precision components, which often are exposed to corrosive media. However, their inferior tribological behaviour restrict the use of these materials in many technical applications. Thermochemical surface hardening is one way to overcome these weaknesses. Solution nitriding in the austenitic range above 1000 °C is mainly used for hardening martensitic and ferritic stainless grades. In austenitic and duplex stainless grades, however, the hardening effect is limited. Additionally, the high process temperatures combined with a necessary rapid cooling may lead to non-desired dimensional changes. Low temperature surface hardening processing below 500 °C here offers interesting alternatives for increasing the wear properties, while maintaining the corrosion resistance. This paper demonstrates the influence of high and low process temperatures of thermochemical surface hardening treatments on the tight dimensional tolerances of a rotationally symmetrical precision component made from cold worked AISI 304. Based on these results, current and new industrial applications, which benefit from low temperature surface hardening, will be discussed.

Thermochemical surface hardening of Ti-6Al-4V: On the role of temperature and treatment media

The present work addresses the surface hardening and heat treatment response of Ti-6Al-4V grades G5 and G23 on thermochemical surface treatment in different temperature regimes as well as in different gaseous and plasma-based media. Grades G5 and G23 were subjected to gaseous surface hardening using various gas compositions and temperature regimes. Two different series of gaseous surface treatments were carried out: 1) Carbo-oxidizing of G23 in mill-annealed condition was performed in CO gas at (high) temperatures ranging from 777 to 1027 °C. Treatment at 1027 °C resulted in the deepest case with the formation of a thin surface layer of titanium sub-oxides supported by a thick TiC x O 1-x layer as the dominant phase. Post-nitriding of the carbo-oxidized specimen raised the hardness of the TiC x O 1-x phase by the incorporation of nitrogen, yielding values up to ~2900 HV and multi-layered structures. 2) Carbo-oxidizing of G5 with a bi-modal microstructure in CO/CO 2 gas mixture at (intermediate) temperatures in the range 677–777 °C. Treatment at 777 °C resulted in a surface hardness of ~1900 HV and a ~60 μm-thick diffusion zone. In addition to gaseous surface hardening, also plasma-assisted methods were applied and compared to their gaseous counterparts. Intermediate- and low-temperature plasma treatments were carried out on G23: 3) Plasma (carbo-nitro)oxidizing was performed in a CO 2 and N 2 gas mixture at 750 °C and (carbo-)oxidizing in CO 2 gas at 650 °C. 4) Plasma nitriding was conducted in a N 2 /H 2 gas mixture at 750 °C and 850 °C. The widely different types of treatments applied in this work represent the diversity of the gaseous and plasma-based thermochemical methods that can be applied for surface engineering of titanium alloys . • Surface hardening of titanium is feasible in widely different temperature regimes. • Hard δ-TiC x O 1-x requires a high a C to form at high temperatures. • High p O 2 maintains a high hardness value in the expanded α at lower temperatures. • Plasma nitriding reduces the required temperature for the formation of hard nitrides. • Temperature is the key factor for surface hardening using CO 2 .

Research of Alternative Options for Strengthening Surface Treatment of Cast Iron Products

The article considers issues of increasing wear resistance of cast iron products by methods of thermochemical treatment of their surface layer. Methods are proposed to solve the problem of wear from cast iron of grade EN-JS1060 due to development of technological processes of strengthening treatment. Alternative versions of strengthening technologies are represented by nitrocarburizing, liquid nitriding and carbonitration. Results of examination of control samples at increasing loads after 200 N before catastrophic wear are given. Comparative analysis of these results showed that samples after carbonitration and liquid nitriding had the greatest bearing capacity (1000 N). Carbonitration is selected as a most preferred option of the surface hardening treatment. Non-poisonous cyanoacid salts are used to realize it.

Syntactic Iron Foams' Properties Tailored by Means of Case Hardening via Carburizing or Carbonitriding.

Metal foam inserts are known for their high potential for weight and vibration reduction in composite gear wheels. However, most metal foams do not meet the strength requirements mandatory for the transfer of sufficiently high levels of torque by the gears. Syntactic iron and steel foams offer higher strength levels than conventional two-phase metal foams, thus making them optimum candidates for such inserts. The present study investigates to what extent surface hardening treatments commonly applied to gear wheels can improve the mechanical properties of iron-based syntactic foams. Experiments performed thus focus on case hardening treatments based on carburizing and carbonitriding, with subsequent quenching and tempering to achieve surface hardening effects. Production of samples relied on the powder metallurgical metal injection molding (MIM) process. Syntactic iron foams containing 10 wt.% of S60HS hollow glass microspheres were compared to reference materials without such filler. Following heat treatments, the samples’ microstructure was evaluated metallographically; mechanical properties were determined via hardness measurements on reference samples and 4-point bending tests, on both reference and syntactic foam materials. The data obtained show that case hardening can indeed improve the mechanical performance of syntactic iron foams by inducing the formation of a hardened surface layer. Moreover, the investigation indicates that the respective thermo-chemical treatments can be applied to composite gear wheels in exactly the same way as to monolithic ones. In the surface region modified by the treatment, martensitic microstructures were observed, and as consequence, the bending limits of syntactic foam samples were increased by a factor of three.

Influence of Deep Rolling and Induction Hardening on Microstructure Evolution of Crankshaft Sections made from 38MnSiVS5 and 42CrMo4

Abstract In order to improve properties of complex automotive components, such as crankshafts, in an application-oriented way, several surface hardening treatments can be applied. Concerning the material performance the definition of adequate process parameters influences the resulting surface properties and, thus, the effectiveness of surface hardening treatments. To analyze most relevant process-microstructure-property relationships, the present paper reports results obtained by two different well-established surface hardening procedures, i. e. deep rolling as a mechanical treatment and induction hardening as a thermal treatment. For each hardening process widely used crankshaft steel grades, i. e. a medium carbon 38MnSiVS5 microalloyed steel and a quenched and tempered 42CrMo4 were selected and thoroughly characterized upon processing, using equal parameter settings. The results reveal that deep rolling in contrast to induction hardening proves to be a less sensitive surface layer treatment with regard to small differences in the initial microstructure, the chemical composition and the applied process parameters. Differences in microstructure evolution with respect to the applied surface hardening treatment are studied and discussed for the highly stressed fillet region of automotive crankshaft sections for all conditions. In this context, high-resolution SEM-based techniques such as EBSD and ECCI are proven to be very effective for fast qualitative evaluation of induced microstructural changes.

Influence of Nitriding Temperature on Mechanical and Tribological Properties of Titanium

One of the commonly used methods for the surface hardening treatment of pure titanium was nitriding. Based on the study of nitriding temperatures on the properties of the pure titanium, some conclusions can be drawn in this paper. The surface hardness of samples after nitriding was gradually increased firstly and then decreased with the processing temperature increasing. And the hardness of the diffusion layer reached the maximum value of 1792 HV when the processing temperature at 1050°C. At the same temperature, the indentation modulus also reached the maximum value of 270 GPa. The wear depth reached the minimum value at 1050°C. At different nitriding temperatures, the minimum of wear depth was 14.8 μm. In summary, when the processing temperature at 1050°C, the nitriding of pure titanium can improve the comprehensive properties.

Analysis of high strength composite structure developed for low-carbon-low-manganese steel sheet by laser surface treatment

In the present work, a high-strength composite steel structure developed by imparting laser surface hardening treatment on a low-carbon low-Manganese automotive steel sheet has been comprehensively analysed. The layered composite steel structure has been successfully developed by re-engineering the surface of the steel using diode laser hardening treatment up to a depth of 250–300 µm through its thickness. Hardness at the treated surface improved by 150% to that of its base due to formation of a mixture of hard phases constituting martensite and bainite along with retained ferrite. Indeed, coupling EBSD technique with Weibull distribution of various phase fractions determined by image quality helped analyse microstructure effectively. The tensile property of the layered composite steel sheet was found to yield significant improvements in both Yield Strength (YS) (40–44%) and Ultimate Tensile Strength (UTS) (19–21%) due to sandwich effect of composite layer constituting hardened layer and soft base accomplished by a strengthening mechanism associated with rule of mixtures concept. In fact, Young’s modulus of the composite steel sheet, determined from slope of tensile stress–strain diagram was found to be convergent with ultrasonic test result. Additionally, the crystallographic texturing effects of the hardened layer and untreated base measured using standard XRD technique re-confirmed their influence on Young’s Modulus and r-bar values obtained.

Phase transformation of austempered and quench-tempered gray cast irons under laser surface hardening treatment

ABSTRACT In this research, the effects of laser surface hardening treatment on the phase transformation of austempered and quench-tempered grey cast irons were investigated. It was found that there were four zones in the matrix of austempered grey cast iron and three zones in the matrix of quench-tempered grey cast iron produced by the laser hardening process. Both cast irons had central laser-hardened zones containing ledeburite (Zone 1) and heat-affected zones (Zone 2) containing martensite. For austempering, an additional heat-affected zone (Zone 3) consisting of tempered ausferrite and a substrate (Zone 4) consisting of ausferrite was formed in the matrix, the dimensions of the laser-hardened and heat-affected regions were independent of the austempering and tempering temperatures. The results reported in this work could be used as a valuable reference for future research on laser-hardened grey cast iron applications. For quench tempering, the substrate (Zone 4) consisted of tempered martensite. Additionally

Bending fatigue strength and impact strength of spur gears with various surface hardening treatments

Bending fatigue strength and impact strength of spur gears with various surface hardening treatments

ПРИЧИНЫ РАЗРУШЕНИЯ БЕССТЫКОВЫХ РЕЛЬСОВЫХ ПУТЕЙ

The main reasons for occurrence of operational defects in continuous welded rail tracks, the main types of their destruction and causes of their occurrence are considered. The technologies for manufacture of the rails are analyzed, including heat treatment along the entire length of the rail, processing the ends of the rail, surface hardening and anti-flake treatment were analyzed.

Effects of plasma nitriding on mechanical, tribological and corrosion properties of friction stir welded joints of Al 2024

The Friction stir welding (FSW) is extensively used to connect Aluminium alloys components in space and aircraft industries. Al 2024is heat-treatable aluminium alloy Al 2024has copper as the primary alloying element which has good mechanical strength and fatigue resistance. Its common application is in aircraft for making various components. In this paper, Plasma Nitrided Al 2024 was joined by Friction stir welding at varying RPM and varying welding speed using cylindrical pin tool and experiment was carried out on different samples (without plasma nitriding on both plates with Plasma Nitriding in one plate& without Plasma nitriding on other plate with Plasma Nitriding process on both plates). The effect of Plasma Nitrided surface hardening treatment on the Al 2024 was done to test the tensile strength, impact strength, wear strength and corrosions of FSW welded joints. The result showed that Plasma Nitriding of Al 2024 improved tensile strength, impact strength, wear resistances and corrosion resistances properties of FSW welded joints.

The Influence of ultrasonic strengthening treatment on microhardness of the construction materials surface with different initial structure

The description of the method of ultrasonic surface hardening treatment (UST), which makes it possible to form gradient structures in structural materials, is given. This paper presents the results of the effect of UST on the surface microhardness of coarse-grained, ultrafine-grained and nanostructured titanium nickelide. The work is devoted to the study of the effect of ultrasonic hardening surface treatment on the surface microhardness of structural materials with different initial structures (coarse-grained, ultrafine-grained, nanostructured).

Determination of the s‐phase formation coefficient of plasma nitrided austenitic steel

AbstractPlasma nitriding is an effective surface hardening treatment for austenitic stainless steels. During plasma nitriding, s‐phase formation takes place which is not only responsible for high hardness and wear resistance but also for good corrosion resistance. In order to estimate the thickness of the s‐phase for austenitic stainless steel in a plasma nitriding process, an empirical model is devised. A number of plasma nitriding processes of austenitic stainless steel (304 L) were carried out with varying treatment temperature from 360 °C to 450 °C and process duration ranging from 10 hours to 24 hours with constant pressure, voltage, pulse‐to‐pause‐ratio and gas mixture. A time‐temperature dependent s‐phase formation coefficient is determined by measuring the thickness of the s‐phase using a scanning electron microscope (SEM) and glow discharge optical emission spectroscopy (GDOES). The developed model is verified by three controlled experiments. This model fits the thickness of the s‐phase with an error of less than 6 %.