Surface Integrity Characteristics Research Articles

Analysis of cutting tool geometry induced machining response, surface integrity and anisotropy relation of additively manufactured 316L stainless steel

Although the machining responses of additively manufactured (AM) materials generally differ from wrought materials due to their microstructural properties, there is no study examining the effects of varying cutting tool rake angles in the machining of AM 316L stainless steel material. The aim of this paper is to evaluate the effects of machining using varying cutting tool rake angles and cutting speeds on the cutting response in terms of cutting force, tool wear, chip morphology and surface integrity characteristics such as microstructure, micro-hardness and x-ray diffraction (XRD) analysis of powder bed fusion – laser beam (PBF-LB) 316L. The effect of the tool rake angle on the anisotropic structure of the material was revealed by examining the machining-induced affected layer from both the built and scan planes and by comparing it with the wrought material. The findings showed that PBF-LB 316L behaves more abrasively than the wrought, creating higher cutting force and tool wear due to the differences in the friction coefficient and thermal conductivity of the materials. Although the machining-induced affected layer is not the same in the built and scan planes of the PBF-LB material due to anisotropy, it is considerably higher compared to the wrought material, especially at negative rake angles. While the hardness of PBF-LB material is higher at a low cutting speed and negative rake angle, the hardening capacity of wrought material is higher at high cutting speed and negative rake angle. PBF-LB chips have repeated adiabatic shear bands and the secondary deformation zone is more evident in wrought chips.

Effect of liquid nitrogen assisted milling on AZ91 magnesium alloy

The objective of the present work is to study the effect of liquid nitrogen (LN2) cryogenic on the performance of face milling for producing quality surface in AZ91 magnesium alloy. Machining AZ91 alloy has been a challenging domain due to the risk of ignition or spark during machining, which affects surface finish. In this study, face milling is carried using uncoated carbide inserts in cryogenic condition, and the performance is compared with dry condition based on the surface integrity (SI) characteristics. The findings of this study reveal that use of LN2 results in enhanced surface integrity. Observations showed no harm to alloy microstructure in both conditions, with no alterations to grain integrity in the near machined area. Cryogenic machining resulted in reduction in machining temperature ranging from 146.7 °C to 178.5 °C, when compared to dry condition temperature ranging from 219.4 °C to 251.2 °C. Cryogenic machining considerably generated smoother (Ra = 0.0606 μm) and harder (HV = 116.5) surfaces, and also resulted in compressive residual stresses. This study concludes that cryogenic-assisted milling is an excellent alternative for the production of superior-quality surface in AZ91 alloy.

Surface Integrity Characteristics and Multi-response Optimization in Wire-EDM of Al–Al3Fe Composites

Surface Integrity Characteristics and Multi-response Optimization in Wire-EDM of Al–Al3Fe Composites

Improving the surface quality of additive manufactured polyamide parts using conventional treatment methods

Additive manufacturing processes have progressed in years past from not only being prototyping methods to also being end-product manufacturing methods. However, there are many challenges hindering higher industrial adoption rates of additive manufacturing such as low surface quality of the manufactured parts. Post-process surface treatment methods can play a key role in addressing this challenge. In this work, three mechanical methods were applied to selective laser-sintered polyamide 12 (PA12) parts with the aim of improving the surface quality. The effects of the methods regarding the surface integrity characteristics were evaluated. The results show improved surface roughness across all three methods: from initial Ra of 7.09 μm to 0.055 μm Ra, 0.28 μm Ra and 0.45 μm Ra by grinding, diamond turning and milling on the surfaces oriented upwards during fabrication respectively. Across the three methods, surface hardness was slightly reduced: with a maximum reduction of 2.5% by diamond turning.

Effect of process parameters involved in SWJP on surface integrity and biocompatibility characteristics of AZ31B Mg alloy

This study mainly investigates the influence of combined parametric conditions employed in submerged waterjet peening for biomedical applications. On measuring the microhardness and roughness on the peened surface, the finding corresponded directly with the strengthening of subsurface layers and different parametric combinations. The optimum parametric combination was determined by TOPSIS, considering microhardness and surface roughness as input. Under optimal parametric combinations, surface morphology and topography analysis, XRD analysis, corrosion behaviour examination, and cell morphology and viability analysis were studied and compared to unpeened surface. From the experimental results, the water bubbles create impulsive pressure that impacts the AZ31B Mg alloy's surface, promoting plastic deformation in the subsurface, enhancing the surface morphological and topographical characteristics, and making the alloy more suitable for bioimplant manufacture. Following that, these samples underwent an electrochemical corrosion study, which indicates the peened region's corrosion rate was reduced considerably compared to the unpeened region. In the course of biocompatibility analysis, the non-toxic nature of the peened region in the MG63 cell line was observed after 24 and 72 h.

A unified model for bending fatigue life prediction of surface-hardened gears

The surface hardness and residual stress (RS) states significantly affect gear bending fatigue, and further mainly determines the reliability of the high-end equipment such as helicopters and electric automobiles. To date, there has been limited research focusing on the study of the quantitative connection between fatigue life and such surface integrity characteristics. In this paper, a damage-coupled gear bending fatigue model based on the continuum damage theory is established to calculate the gear fatigue life considering RS and hardness states. Then, unified gear bending stress-life (S-N) equations originating from the Basquin equation are derived to evaluate the quantitative effects of RS and hardness on gear bending fatigue life. The RS and hardness impact coefficients in unified equations are determined using the fatigue data obtained from a gear damage-coupled model. The unified gear bending S-N curves are verified using the experimental fatigue life data of shot peening and un-peening gears. These lead to the establishment of the unified equation integrating both the residual stress and surface hardness states for 18CrNiMo7-6 gear.

Modeling and Optimization of Surface Integrity and Sliding Wear Resistance of Diamond-Burnished Holes in Austenitic Stainless Steel Cylinder Lines

This article outlines a technology for hole-finishing in short-length cylinder lines to improve wear resistance. The technology is based on an optimized diamond-burnishing (DB) process. The latter was implemented on conventional and CNC lathes, milling machines, and machining centers using a simple burnishing device with an elastic beam. The material used in this study was AISI 321 austenitic stainless steel. The governing factors used were the radius of the diamond insert, burnishing force and feed rate. The objective functions relating to surface integrity characteristics were selected on the basis of their functional importance relative to the wear resistance of the processed hole surface: height and shape roughness parameters, surface microhardness, and surface residual axial and hoop stresses. The one-factor-at-a-time method (used to reduce the factor space), a planned experiment, and regression analyses were used. The multi-objective optimization tasks, which were defined for three diamond insert radius values of 2, 3, and 4 mm, were solved via the Pareto-optimal solutions approach available for a non-dominated sorting genetic algorithm (NSGA-II). Using the optimal values of the governing factors selected from the Pareto fronts, cylinder lines were processed. Samples were then cut from these cylinder lines for reciprocating sliding wear tests under two modes: dry friction and boundary lubrication friction. Additionally, wear test samples were cut from the cylinder line, which was finished with traditional grinding. A finite element simulation was then used to select an appropriate pressing force. The results obtained from the reciprocating sliding wear tests under both the dry and boundary lubrication friction regimes show that to minimize the wear on cylinder lines made of AISI 321 steel, DB with a diamond insert of radius 2 mm is the optimal finishing process.

Surface integrity and acoustic emission characteristics during slot milling 3D carbon/carbon composites using superabrasive diamond grinding point

This study mainly investigated the effect of machining parameters on surface morphology and defects in three-dimensional carbon/carbon ceramic matrix composites during slotting with superabrasive diamond grinding points. Specifically, it discussed the mechanisms of burr and uncut fiber formation based on the relationship between grinding and fiber directions. The experimental work was conducted under different spindle speeds and feed speeds, revealing that the poor machining surfaces and severe defects occurred at the minimum spindle speed (2000 rpm) with maximum feed speed (160 mm/min), and most uncut fiber defects occurred when the fiber cutting angle exceeded 90°. Acoustic emission (AE) signals were analyzed via signal processing techniques to capture the energy and frequency characteristics of slotting process under various machining parameters. Results indicated that spindle speed had a significant impact on the frequency band distribution of AE signals, while feed speed primarily influenced the stability of signal profiles. The material removal and tool wear mechanisms were examined through SEM micrographs of machined surfaces and grinding points, revealing that fiber debonding and fracture were the primary material removal mechanisms, and were highly dependent on the fiber cutting angle. Abrasive particles with relatively lower cutting velocity at the center of the grinding tool suffered severe damage/wear.

Correlation between surface integrity characteristics in high-speed grinding of Ti-6Al-4V

The present article establishes a fundamental correlation between surface integrity characteristics of the finished surface with the normal to tangential force ratio (Fn/Ft) in the grinding of Ti-6Al-4V. The subsurface deformation, crystallographic texture, surface redeposition, and residual stress were studied in the surface integrity characteristics. The XRD result indicated deformation-induced texturing of the α-002 basal plane of Ti-6Al-4V. The gradual reduction in texturing along the depth was confirmed by the Gi-XRD investigation. The relative intensity of the 002 peak was utilized as a quantitative indicator of subsurface deformation. The XRD and the metallographic study revealed a considerable amount of subsurface deformation at a higher grinding speed (vs ) and an enhanced material removal rate (MRR). Intense surface redeposition was also observed for higher vs and increased MRR grinding conditions. The surface redeposition was identified as an influencing factor that escalates the subsurface deformation and crystallographic texture. In addition, the residual stress was found to be more compressive at enhanced vs and MRR. Further, a higher force ratio Fn/Ft was noticed for the grinding conditions that revealed significant subsurface deformation, strong crystallographic texture, surface redeposition, and more compressive residual stress. Eventually, a correlation was found between the force ratio Fn/Ft and all these surface integrity characteristics.

Influence of advanced coated tools on surface integrity characteristics of Nimonic C263

Advanced coated tool and cooling techniques were used for trial on Ni-based superalloy Nimonic C 263 to improve surface integrity, such as a white layer, grain refinement, and surface defect. Toolmaker microscope, Field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) system were employed to characterize the tool after machining, machined surface, and subsurface alteration. A possible cause of tool failure at high cutting speed and feed was severe plastic deformation and chipping of the cutting edge and nose, abrasive nose and flank wear, and the formation of a built-up layer (BUL). The white layer, surface defect, and grain refinement are always found less on machined surfaces with the PVD-coated tool under dry machining than with an uncoated tool under wet machining at a high rate. TiN/TiAlN multilayer coated WC tool can be suggested for good machinability and surface integrity in a sustainable, eco-friendly way to the industry for machining Nimonic C-263. MQL and flood mode cooling are also preferred at a cutting speed near 84 m/minute and a feed rate of 0.14 mm/rev.

Influence of Maghemite (γ-Fe2O3) Nano-Powder Mixed Micro-EDM on the Surface Integrity Characteristics of Co-Cr-Mo

Surface integrity in electric discharge machining (EDM) has always been a major concern in the manufacturing industry. Although EDM with powder suspended dielectric has shown good potential in enhancing material removal rate and improving surface finish, the influence of the same on overall surface integrity is not very clear. The current work utilized (γ-Fe2O3) nano-powder and evaluated its role in combination with concentration and machining parameters, on surface roughness (Ra, Rmax), surface crack and thickness of recast layer, during powder-mixed micro-EDM (PMµEDM) of Co-Cr-Mo. SPM data are obtained through the database and its morphologies and meteorology are studied using the gwyddion software. Results showed that significant reduction in surface roughness, crack density and recast layer thickness is possible with the PMµEDM process.

Cryogenic ultrasonic vibration assisted turning to texturize AZ31 magnesium alloy surfaces

Magnesium alloys are increasingly used in the biomedical field thanks to their biocompatibility. However, poor corrosion resistance greatly limits their applications. Coating the devices is known to represent the most efficient way to increase the corrosion performances of magnesium alloys, but it requires specific surface preparation of the metal substrate. In the present paper, a hybrid machining technology, namely cryogenic–ultrasonic-assisted turning, is applied to generate magnesium alloy texturized surfaces with enhanced surface integrity characteristics. Results showed that the application of liquid nitrogen led to a harder and more complex surface texture than in the case of ultrasonic-assisted turning under dry conditions.

Microstructural and mechanical properties evolution of 690 nickel-based alloy subjected to severe hand disc grinding conditions

This present experimental research paper investigates the effects of severe hand disc grinding conditions on microstructure and mechanical properties evolution of a nickel-based alloy. Hand grinding is an abrasive process widely used in manufacturing industry. This manual process is used for different surface geometries, and it is often applied as the final operation that provides the effective physico-chemical properties of the surface and its sub-layers. To study the effects of manual disc grinding, a prerequisite consists in identifying the manufacturing parameters such as the feed, the normal force and the orientation of the tool with the manufactured surface. Which is neither easy to reproduce from one operator to another knowing the manual aspect of this manufacturing process nor rigorous to carry out a repeatable experimental plan. Therefore, a test bench with independent controlled parameters is required to reproduce the manual grinding process and achieve advanced studies. Mechanical properties and microstructural evolutions of a nickel-based alloy ground under very high thermomechanical loading due to abrasive material removal process were investigated through micro-hardness, XRD, SEM, EDS and EBSD analysis. The typical surface integrity characteristics are presented. Qualitative and quantitative EBSD measurements were performed to evaluate the local strain condition of the material after extreme thermomechanical processing on subsurface integrity of the nickel-based alloy. The microstructure of the material in the modified layer consists of a highly refined grain structure with an enhanced microhardness of up to 75% compared to the bulk material. It is assumed that the first 20 μm of the modified layer also called white layers in nickel-based alloy are formed by severe plastic deformation during material removal process. Keywords: surface integrity, nickel-based alloy, hand disc grinding, severe plastic deformation, grain refinement, SEM, EBSD. • Multi-scale and multi-physic surface characterization approaches to understand severe disc grinding-induced material modifications of nickel-based alloy. • A gradient of material mechanical properties occurred involving changes in its yield strength. • XRD and micro-indentation are complementary techniques to characterize the work-hardened layer induced by disc grinding. • Thermomechanical effects from disc grinding lead to severe plastic deformations of the metal workpieces yielding highly deformed grain structure, severe work hardening resulting in grain refinement under severe cutting conditions. • Presence of disc grinding-induced surface defects such as ductile tearing, material re-deposition (micro-welding) and debris are also concerns which can deteriorate functional performance of components. • SEM and EBSD analyses revealed the presence of a cold-worked layer consisting of a partially nanostructured region generated during grinding by the combination of a severe plastic deformation and high thermal kinetics.

Study on the Changing Law of Cutting and Ultrasonic Strengthening Surface Integrity during Fatigue of Ti-17 Alloy.

The distribution of surface integrity features directly affects the initiation and propagation of fatigue cracks. In this paper, the surface integrity characteristics changing law of turning and ultrasonic impacting specimens during high cycle fatigue loading has been studied, and the effect of surface modified layer on the fatigue properties of titanium alloy has been revealed. The results showed that the surface roughness increased with the increase of fatigue cycles. The compressive residual stress and its gradient distribution depth decreased continuously. The gradient distribution depth of residual stress in the ultrasonic-impacted surface rapidly decreased by about 50% near the fracture stage. Local cyclic hardening occurred at 20-50 μm from the surface of the specimen in the early stage of fatigue evolution, and then the microhardness continued to decrease. During this process, there were no significant changes in hardened layer depth. The fibrous microstructure of the ultrasonic-impacted surface undergoes a process from coarsening to gradual disintegration during the fatigue process. Its attenuation process needs a longer period of time. The fatigue source of the turned specimen was located at about 320 μm from the surface, and the fatigue source of ultrasonic impact was about 610 μm from the surface. The fatigue striation width of the ultrasonic impact specimen was about 20% narrower than that of the turned specimen. The fatigue life of the ultrasonic impact specimen was increased by 73.9% compared with the turned specimen. The research in this paper is of great significance for exploring the anti-fatigue mechanism and the ability of various surface integrity features.

Surface integrity characteristics in wire-EDM of HfTaTiVZr refractory high entropy alloy

ABSTRACT Refractory high entropy alloys (RHEAs) with multiple principal elements constitute a new paradigm in alloy design and have gained recent interest for advanced technical applications due to their unique properties and mechanical stability at high temperatures. However, the refractory metals that make up these alloys are pretty expensive, and they cause RHEAs to exhibit low plasticity behaviour at room temperature. The high stability properties of RHEAs from room temperature to high temperatures limit their machinability with traditional cutting methods. Therefore, it is vitally important to economically machine these alloys while preserving their mechanical properties and minimising waste. For this purpose, in this study, the machinability of a HfTaTiVZr RHEA was evaluated with wire electric discharge machining (WEDM). The surface morphology, crack formation, and mechanical characteristics of the surface layer were investigated as a function of three different cutting conditions: rough cutting, semi-finishing, and finishing. The RHEA was precision cut in three passes by reducing the volume of material in each pass, resulting in better surface quality with the optimal cutting speed and metal removal rate. However, rough cutting gave better results than semi-finish and finished cutting processes in preserving mechanical properties.

Enhancing the surface integrity characteristics of Al-Li alloy using face milling

• The work explores the potential of one of the most demanding alloy (Al-Li) in the aerospace sector. • Milling process has the ability to improve the functional performance of the alloy to a great extent. • Great surface integrity characteristics in terms of roughness, hardness and residual stress. • Limited microstructural damage can be expected from milling process. • Very limited prior studies on the machining induced behaviour of this alloy. This work presents the milling induced surface integrity investigation of Al-Li alloy. The effect of milling on the surface roughness, microhardness, microstructure, and residual stress is studied. Uncoated carbide inserts are used for milling due their superior hardness and greater life, when machining softer materials such as aluminium and its alloys. Results show that the minimum surface roughness (Ra = 0.043 µm) and maximum microhardness (216 HV) are achievable from the milling process, when compared with the roughness (Ra = 0.528 µm) and microhardness (180 HV) of the as-received material. Results indicate limited harm to alloy microstructure from the milling process and the presence of compressive residual stress induced from milling. The work finds scope for aerospace applications.

Effect of High-Speed Dry Face Milling on Surface Integrity Characteristics of AZ91 Mg Alloy

Effect of High-Speed Dry Face Milling on Surface Integrity Characteristics of AZ91 Mg Alloy

Development of customized physics-based predictive models for improved performance in turning of Ti6Al4V

This paper presents a combination of numerical and analytical models for selection of optimal parameters on turning Ti6Al4V. In particular, the work demonstrates the efficiency of the combined models to properly design the process tremendously reducing the time requested to verify the final product characteristics. The applied models include the prediction of surface integrity characteristics such as grain size, hardness changes and residual stresses but also fatigue life prediction based on surface characteristics. The above models have been modified and updated according to the material characteristics, centered on physics-based equations and assumptions, process and phenomena taken into consideration for the specific setup. In particular, the models follow the overall process starting from the cutting phase up to the final fatigue operational performance. The proposed approach demonstrates that it is possible to predict, with adequate accuracy, the influence of the machining process on surface state and final performance in terms of fatigue life. Thus, it is possible to drastically reduce the time and efforts to build up knowledge based on experimental trials including the proposed models into an industrial context.

Effect of Diamond Burnishing on Fatigue Behaviour of AISI 304 Chromium-Nickel Austenitic Stainless Steel.

The disadvantages of widely used austenitic stainless steels are their low hardness and relatively low fatigue strength. Conventional chemical-thermal surface treatments are unsuitable for these steels since they create conditions for inter-granular corrosion. An effective alternative is a low-temperature surface treatment, creating an S-phase within the surface layer, but it has a high cost/quality ratio. Austenitic steels can increase their surface micro-hardness and fatigue strength via surface cold working. When the goal is to increase the rotating bending fatigue strength of austenitic chromium-nickel steels, and the requirements for significant wear resistance are not paramount, diamond burnishing (DB) has significant potential to increase the fatigue strength and, based on the cost/quality ratio, can successfully compete with low-temperature chemical-thermal treatments. The main objective of this study is to establish the effect of DB on the rotating fatigue strength of AISI 304 L chromium-nickel austenitic steel. The influence of DB parameters on the surface integrity (SI) characteristics was studied. Optimal DB parameters under minimum roughness and maximum micro-hardness criteria were obtained. Rotating bending fatigue tests of the diamond burnished (in a different manner) and untreated specimens were performed. DB implemented via parameters providing maximum micro-hardness increased fatigue limit by 38% compared to untreated specimens.

A comparative analysis of chip shape, residual stresses, and surface roughness in minimum-quantity-lubrication turning with various flow rates

In this research, an experimental investigation was carried out to investigate the interaction between various turning parameters and different minimum quantity lubrication (MQL) flow rates and compare their effects on chip shape and surface integrity characteristics in low speed turning and high speed turning of AA6061-T6. The turning parameters included cutting speed, feed rate, and depth of cut. The flow rates comprised 3.5 $$\mathrm{ml}/\mathrm{min}$$ , 10 $$\mathrm{ml}/\mathrm{min}$$ , and 15 $$\mathrm{ml}/\mathrm{min}$$ , and the surface integrity characteristics consisted of average arithmetic surface roughness, height peak from the valley, and axial and hoop surface residual stresses. The results showed that cutting conditions including cutting speed, feed rate, and depth of cut affected chip shape, while MQL flow rate had no impact on chip shape. The lowest values of cutting speed, feed rate, and depth of cut, equal to 145 $$\mathrm{m}/\mathrm{min}$$ , 0.07 $$\mathrm{mm}/\mathrm{rev}$$ , and 0.66 $$\mathrm{mm}$$ , respectively, resulted in the smallest residual stresses for all the flow rates. Moreover, the smallest surface roughness parameters were obtained at the lowest feed rate (0.07 $$\mathrm{mm}/\mathrm{rev}$$ ) for all the flow rates, whereas there were high interaction effects between cutting speed and flow rate and depth of cut and flow rate. Finally, turning with the minimum quantity lubrications of 3.5 $$\mathrm{ml}/\mathrm{min}$$ and 10 $$\mathrm{ml}/\mathrm{min}$$ , respectively, is suggested to obtain the best overall surface integrity characteristics. These lower values of flow rate are suitable to reduce machining costs, protect the environment, and preserve the machinist’s health. Since most of the previous research studies focused on the comparison of the turning environments including dry, MQL, wet, and cryogenic and only a few research works on the comparative analysis of MQL turning with different flow rates were carried out, the results of the present research can be utilized as a reference for future works in this field.