Effect Of Surface Hardening 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.

The effect of ultra-fast surface hardening and strengthening on microstructure and mechanical properties of cast (9Cr–3Co–3W) heat-resistant steel

The effect of ultra-fast surface hardening and strengthening on microstructure and mechanical properties of cast (9Cr–3Co–3W) heat-resistant steel

The effects of sucrose/NaCl combined pickling on the textural characteristics, moisture distribution, and protein aggregation behavior of egg yolk.

Salted egg yolks have a tender, loose, gritty, and oily texture and are commonly employed as fillings in baked goods. This study investigated the formation mechanism of egg yolk gels using three different pickling methods: NaCl, sucrose, and mixed groups. The results revealed that of these pickling methods, egg yolks pickled with the mixture had the lowest moisture content (11.59% at 25°C and 10.21% at 45°C), almost no free water content, and the highest hardness (19.11 N at 25°C and 31.01 N at 45°C). Intermolecular force measurements indicated that pickling with the mixture mitigated the surface hardening effect of sucrose and facilitated protein cross-linking. Moreover, confocal laser scanning microscopy of the egg yolk gels pickled with the mixture displayed macromolecular aggregates and oil exudation, suggesting that this method partially disrupted the lipoprotein structure and notably promoted yolk protein aggregation and lipid release. Overall, egg yolks formed a dense gel via the mixed pickling method owing to the ionic concentration and dehydration effects. These findings show the impact of NaCl and sucrose in pickling egg yolks, providing a crucial foundation for developing innovative and desirable egg yolk products. PRACTICAL APPLICATION: This study introduces a novel pickling strategy that combines sucrose and NaCl for egg yolk processing. The egg yolk pickled using this method exhibited improved quality according to the evaluated textural characteristics, moisture distribution, and protein aggregation behavior. The findings may broaden the use of sucrose as a pickling agent for egg yolk processing and provide new ideas for developing and producing pickled eggs and other food products.

Strategy and mechanism to improve the fatigue properties of Ti6Al4V ELI alloy by microstructure modulation combined with surface strengthening process

The hot isostatic pressing (HIP) technique allows obtaining powder metallurgy Ti6Al4V parts with high densities, but its microstructure is not ideal, resulting in a lower fatigue life than expected. In this work, the ideal microstructure was obtained by heat treatment, but this process produces thermally induced porosity (TIP). After heat treatment, the fatigue strength of the bimodal Ti6Al4V alloy reached 680 MPa at 107 cycles, whereas the HIP Ti6Al4V alloy with a fully equiaxed microstructure was lower than 590 MPa. This is because the bimodal Ti6Al4V alloy has better resistance to fatigue crack initiation. This result confirmed that TIPs do not have a significant negative impact on fatigue properties. To further improve the fatigue performance, this study induced gradient nanostructured (GNS) in Ti6Al4V alloy by ultrasonic surface rolling process (USRP), and the fatigue strength of the USRP-treated specimen reached 750 MPa at 107 cycles. Combining microstructure observations and theoretical analysis, the surface hardening mechanism of the USRP-treated Ti6Al4V alloy was quantitatively described. The results showed that the plastic deformation layer is approximately 130 μm, but grain boundary strengthening maintained its effect to a depth of about 200 μm whilst dislocation strengthening maintained its effect to a depth of approximately 350 μm. Under the comprehensive effect of surface hardening and compressive residual stress field, the fatigue crack initiation period of the USRP specimen was significantly extended. This may be the primary reason behind the enhanced fatigue performance obtained through USRP treatment.

Effects of surface hardening on hardness and tensile strength of locally manufactured feed mill hammers

Animal feed is a major production cost of raising livestock and accounts for about 65 - 68 % of the total production cost, mainly ingredients and processing costs. During feed manufacturing, a hammermill is required for the grinding process to produce quality feed. However, the absence of durable hammers on the local market in Ghana and the high cost of imported hammers compels feed producers to resort to locally manufactured hammers which wear fast due to poor quality of the material. This study considers the application of two surface hardening techniques: (i) carburizing (charcoal and Barium Carbonate (BaCO3) as activator) and (ii) carbonitriding (charcoal, NPK fertilizer as a nitrogen source and Barium Chloride (BaCl2) as activator) in combination with three different quenching media (water, air and oil), to improve the material properties of locally produced hammermill hammers. The surface hardening experiments were performed at 900 oC for 3 h after which the samples were quenched. Tempering was performed afterwards at 160 oC for 1 h. Carbonitriding and water quenching treatment had the best effect on hardness and tensile strength of all the treatments. It yielded the highest surface hardness and tensile strength of 410.06 HV and 768.79 MPa, respectively, representing about a 218 % increase in hardness and a 47 % increase in tensile strength compared to the control sample, which were 128.92 HV and 522.41 MPa, respectively. The result implies hammers produced with this carbonitriding surface hardening and water quenched technique would have improved hardness and wear resistance compared to untreated hammers.

Effect of Repeated Processing Passes during Ultrasonic Rolling on Fatigue Performance and Corrosion Resistance of Ti6Al4V Alloy

Ultrasonic surface rolling processing (USRP) is a new method to improve the fatigue performance of titanium alloy, and repeated processing pass is an important factor that affects its strengthening effect. The effect of USRP passes on the surface microstructure, residual stress, fatigue performance and corrosion resistance of titanium alloy is researched via SEM, X-ray diffractometer, rotating–bending fatigue test and electrochemical impedance spectroscopy. The results show that Ti6Al4V alloy undergoes cumulative plastic deformation during USRP process, the surface grains are refined and a residual compressive stress field with a thickness of 500 μm is introduced, which together improve the fatigue performance of the Ti6Al4V alloy. Increasing the repeated processing passes will deepen the grain refinement layer and increase the surface hardening effect, but the fatigue life of the Ti6Al4V alloy does not increase with an increase in processing passes. A five-passes processing under a static force of 550 N can result in a greater gain for the fatigue resistance of the Ti6Al4V alloy; the fatigue life of a five-passes-processed sample under 600 MPa is 8 times higher than that of an untreated sample, and its fatigue crack source initiates at the subsurface away from the surface of 180 μm. Furthermore, Ti6Al4V alloys treated by USRP show a better corrosion resistance in both neutral and acidic solutions, especially for the five-passes-processed sample.

Tribological considerations for failure restoration and maintenance of radial plunger pump against friction and abrasive wear behavior by microwave cladding of Ni-Graphene

Clean and efficient manufacturing techniques are in great demand in modern industrial facilities. New methods are being developed which are cleaner, environment-friendly, economical, and have better mechanical properties, among others. Due to hot corrosion, Tribological components are often subjected to wear and tear. Graphene (Gr) is a promising material with microwave absorption performance due to its self-lubricating properties, low density, and cementite (Fe3C) formation capabilities with iron. This work examined the effect of self-lubricating behavior and surface hardening of plungers of Austenite alloy by Ni-Gr cladding and glazing. Using silicon carbide abrasive media, a pin-on-disc wear tester was utilized for abrasion testing. Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) analysis supplemented with a microhardness test were performed to measure the improvement in the properties of clad samples. The results showed that temperature variation influences phase change and mechanical properties. The Ni-Gr cladding showed dense eutectic microstructure at 750° C. XRD’s results revealed that the disintegration of the cladding layer is reduced due to heat treatment along with the generation of the Fe3C phase. In addition, the deposited specimen confirmations maximum wear resistance and hardness characteristics with a minimum wear rate at 750 °C, just above the steel's first critical temperature.

Effect of Surface Impacting Parameters on Wear Resistance of High Manganese Steel

High manganese steel has always been subjected to pre-hardening treatment before use owing to its low initial strength. Therefore, cast high manganese steel was pre-hardened in this work by surface impacting treatment under different parameters to evaluate its state. The microstructures, hardening characteristics, and wear resistances of the pre-hardened high manganese steel samples were all investigated. The results indicated that increasing the sample temperature, reducing the impact pin size, and increasing the impact times on a single-point can enhance the surface hardening effect to different degrees. Dislocations and deformation twins were produced on the top surface and within a certain depth of test steel under different impacting conditions. The optimal hardening effect of test steel was achieved at a temperature of 300 °C, a pin size of 10 × 10 mm2, and 9 impacts on a single point. The surface hardness of the treated sample reached 542 HV. For friction and wear testing, the best wear resistance was achieved at a temperature of 300 °C, a pin size of 10 × 10 mm2, and 3 impacts on a single point with a surface hardness of 446 HV. Further enhancement in impact hardening effect resulted in microcracking along the surface of test steel. In turn, the induced embrittlement led to the poor wear resistance.

Surface hardening effect on the fatigue behavior of isotropic beam

Surface hardening effect on the fatigue behavior of isotropic beam

Laser Surface Hardening of Graphite Cast Iron

Two types of graphite cast iron are evaluated. The effect of laser surface hardening is compared using metallographic analysis of the microstructure and measurement of hardness profile. Conditions of the hardening were the same for both analyzed materials. The alloys that were compared are: cast iron with lamellar graphite EN GJL-200 and cast iron with nodular graphite EN GJS-700 CuNi. Microstructure of tested cast irons was pearlitic-ferritic. Laser surface heat treatment caused formation of martensitic layer. The depth and structural compositions of hardened layers do differ. In the case of gray cast iron the higher hardened depth was achieved and in the case of ductile cast iron the higher hardness was observed.

INVESTIGATION OF MICROSTRUCTURAL AND MECHANICAL PROPERTIES OF CARBURIZED GENERAL CONSTRUCTION STEEL

In this study, the effect of surface hardening on microstructure and mechanical properties was investigated by applying box carburizing (cementation) process to samples produced from unalloyed St37 steel, known as structural steel. In the experiment, the samples, which took place at 2 different temperatures at 800 ºC and 930 ºC, were kept in the oven with coal dust in the box for 3, 5 and 10 hours for cementation, with the mouth tightly closed. By examining the microstructure of the cemented samples, the coating thicknesses, hardness changes by making hardness tests, and the amount of wear were examined by performing abrasion tests. As a result of the vickers method hardness tests, it was revealed that the highest hardness values were found in the sample that was cemented for 10 hours at 930 ºC. As a result of the wear tests, 10N and 20N loads were applied to the sample, and the wear amount of the wear device on the material was found by traveling 100 m at a stroke distance of 10 mm. As a result of the wear tests, the applied cementation time and the wear loss are inversely proportional, while the cementation temperature value is inversely proportional to the wear loss. It has been determined that the applied load and the wear loss are directly proportional.

EFFECT OF THE STRUCTURE FORMED AFTER BULKAND SURFACE HARDENING ON THE HARDNESSAND WEAR RESISTANCE OF 20Cr2Ni4A STEEL

The article presents the results of a comparative study of the effect of bulk and surface hardening on the structure and properties of 20Cr2Ni4A steel. Surface hardening was carried out by the electrolytic plasma method. Bulk quenching was carried out by heating to a temperature of 870 °C, followed by cooling in water and oil. The structural-phase states of20Cr2Ni4A steel samples were studied by metallographic and X-ray structural analysis. Tribological tests of the samples were carried out according to the ball-disk scheme, and the microhardness of the samples was also determined. It has been determined that after volumetric and surface hardening, the hardness and wear resistance of 20Cr2Ni4A steel increase. In this case, the most significant change is observed in samples that have undergone electrolytic plasma hardening. It has been established that high values of hardness and wear resistance of 20Cr2Ni4A steel after electrolytic plasma hardening are associated with the formation of fine-needle martensite

Introducing gradient severe shot peening as a novel mechanical surface treatment

Shot peening is widely used for improving mechanical properties especially fatigue behavior of metallic components by inducing surface hardening, compressive residual stresses and surface grain refinement. In air blast shot peening, projection pressure and surface coverage (an index of peening duration) have been considered as major controlling process parameters; the combination of these parameters plays a critical role in the beneficial effects of shot peening. Generally in severe shot peening aimed at obtaining surface grain refinement, constant values of pressure are considered with different peening durations. Considering very high peening duration, however, the phenomenon of over shot peening, which can be identified with the formation of surface defects could occur. The present study introduces a novel shot peening treatment, here called gradient severe shot peening (GSSP) that instead of using constant projection pressure, implements gradually increasing or decreasing pressures. The gradual increase of the projection pressure acts as a pre-hardening stage for the following higher projection pressure boosting the potential of the material to tolerate the sequential impacts and thus become less prone to the formation of surface defects. The results of the experiments indicate significant fatigue life improvement obtained for GSSP treated specimens compared to the standard treatment with constant pressure. GSSP avoids the detrimental effects of over-peening, while maintaining the beneficial effects of surface nano-crystallization, surface hardening and compressive residual stresses. The notable difference in fatigue strength enhancement for GSSP treated material can be also attributed to the modulated surface morphology with lower surface roughness compared to a standard shot peening treatment with the same exposure time.

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.

STUDY OF CHANGE IN WEAR RESISTANCE OF STAINLESS STEEL SURFACE OBTAINED BY LASER PULSE ALLOYING IN THE COATING LAYER

The paper describes an experimental study of laser pulsed modification of the surface of stainless chromium-nickel steel of the austenitic class 12Cr18Ni10T with a graphite coating previously applied to it. The microhardness of the treated surface and its dependence on the modes of laser radiation were determined. The abrasion method was used to study the change in the wear resistance of the modified layer and the possibility of its increase. For a quantitative assessment of the surface resistance to wear, a gravimetric analysis of samples subjected to ball abrasion was carried out, the results of which are fully consistent with the calculation of the dimensionless wear resistance index. It was found that the value of the microhardness is largely influenced by the voltage of the pulses. Thus, the highest microhardness indicators were observed during processing by laser pulses in the voltage ranges of 250-280 V and 340-440 V and take values of 5-6 GPa and 4-5 GPa, respectively. A comprehensive study of abrasion resistance, including the calculation of a dimensionless wear resistance index and an analysis of the weight loss of steel samples as a result of the test, showed that, to the greatest extent, the surface hardening effect is characteristic of samples subjected to treatment with laser pulses focused into a spot 1 mm in diameter at a pulse voltage of range 300-400 V.

Discrete Oxidation of a Hard Carbide Tool

Comparative investigations of the effect of discrete surface hardening by standard ion-plasma technology and discrete oxidation technology on the structure and hardness of high-speed steels are carried out. It is shown that, after hardening in the ion-plasma installation on the surface and in the thickness of the layer, droplet-shaped defects, craters and bundles are formed. Metallographic studies showed that the hardened discrete oxidation layer after repeated hardening has a dense, uniform structure. It has been established that the discrete oxidation technology allows to increase the wear resistance of a complex-profile cutting tool 2 times more, compared to a tool hardened by standard ion-plasma technology after regrinding.

COMPARATIVE ANALYSIS OF THE INFLUENCE OF THE COMPOSITION OF THE ALLOYING COVERING ON THE CHANGE IN THE STRUCTURE AND MICROHARDNESS OF STAINLESS STEEL 12KH18N10T

The article is devoted to the experimental analysis of the influence of the process of laser pulsed alloying in a layer of alloying mixture on the qualitative and physical and mechanical characteristics of the modified surface of stainless chromium-nickel steel of the austenitic class 12Cr18Ni10T. It was found that the use of graphite paste as an alloying compound leads to a significant increase in microhardness, a change in micromorphology, and the formation of a heat hardening zone in the near-surface layer of steel. The smoothing of the boundaries of structural changes is revealed and the effect of surface hardening is determined when a finely dispersed powder of titanium dioxide (anatase) is added to the alloying coating. According to the data obtained, a comparative analysis of the dependence of the microhardness of the modified surface on the voltage of the pump lamp and the diameter of the laser pulse spot is carried out. The maximum microhardness value, equal to 9,56 GPa, was achieved as a result of laser processing of a series of samples, where graphite paste was applied as a preliminary surface preparation. Rational technological modes of laser modification of the surface of 12Cr18Ni10T steel that have previously undergone abrasive blasting, modes of laser pulsed alloying in a layer of graphite coating and laser pulsed alloying of steel in a layer of coating consisting of graphite paste and anatase powder in a ratio of 4:1, respectively, are recommended.

Development Research on Integrating CNC Machine Tool with Plasma for Online Surface Heat Treatment

In this study, the plasma was integrated with a lathe, and the online heat treatment was performed to achieve mechanical strength and hardness, to reduce the machining process and handling. However, for online heat treatment of cast iron FC25, it is important to study the parameters of the lathe and plasma, and the research method is used eventually to optimize the process and reduce the machining cost and machining error. The variable factors in the surface online real‐time heat treatment are spindle speed, feed rate, and current, and the objective function is the hardness of mechanical properties. In the screening experiment, the interaction of factors was discussed using a full factorial experiment. The Central Composite Design was combined with the Lack‐of‐Fit test for the optimization experiment, and the R2 coefficient was used to determine whether the regression model is appropriate. The optimum parameters were derived from the contour diagram and response surface diagram. The experimental results show that the significant factors include spindle speed, feed rate, and current and the optimum parameters include spindle speed of 168 rpm, feed rate of 0.068 mm/rev, and current of 86 A. The experimental results of optimum parameters show that the surface hardness is increased from 306 HLD to 806 HLD and the surface hardening effect is enhanced by 163%, so the online real‐time heat treatment equipment has the best hardening effect.

Increased Wear Resistance of High-Speed Tools Due to Diffusion Discrete Oxidation

Comparative studies of the effect of discrete surface hardening by standard ion-plasma technology and discrete oxidation technology on wear resistance have been carried out. Metallographic studies have shown that discrete oxidation has a polycrystalline structure. It was found that the technology of discrete oxidation makes it possible to increase the hardness by 31% in relation to the uncoated material, and the wear resistance of the cutting tool with oxidation is 1.5-3 times higher than that of the tool hardened by the standard ion-plasma technology.

Effect of ultrasonic impact treatment on the surface integrity of nickel alloy 718

Ultrasonic impact treatment (UIT) is a type of surface strengthening technology that can improve the fatigue properties of materials by improving the surface quality, residual stress, and other aspects. In this study, the influence of ultrasonic impact parameters on the surface integrity of nickel alloy 718 was studied. The micro stress concentration caused by the surface morphology was also explored. The cosine and exponential decay functions were used to fit and characterize the distribution of residual stress and work hardening in the surface material. The results showed that the feed rate had the greatest influence on surface roughness, stress concentration, and surface residual stress. It was not appropriate to evaluate the surface hardening effect only by the number of impacts per unit area, the ultrasonic impact parameters such as feed speed and pre extrusion depth should also be considered. The grain refinement was obvious after UIT. The multi-objective optimization of machining parameters was performed with the objective of surface stress concentration and residual stress. A surface with a smaller surface stress concentration factor and larger compressive residual stress can be obtained simultaneously using medium linear velocity, medium pre extrusion depth, and smaller feed rate.