Characterization Of Surface Integrity Research Articles

Multi-physics field coupling interface lubrication contact analysis for gear transmission under various finishing processes

Surface integrity is crucial for the load-bearing capacity, transmission performance, and service life of gears. Finishing processes can effectively improve surface quality and are widely used in gear manufacturing processes to enhance surface integrity and improve the service performance of gears. Five precision machining tests of form grinding, vibratory finishing, barrel finishing, honing, and abrasive flow machining were conducted on spur gears. High-precision surface integrity characterization methods were used to analyze the surface integrity parameters of the finished gear surfaces, including surface roughness, surface microtopography, residual stress, texture aspect ratio, roughness peak curvature radius. The finishing processes uniformity and effectiveness of the tooth profile surface were also evaluated. By using the finished rough surfaces as inputs and considering the impact of thermal elasto hydrodynamic lubrication on the gear surface, a multi-field coupling contact analysis model encompassing solid, liquid, and thermal fields at the gear meshing interface was established. Lubrication performance parameters such as oil film pressure, oil film thickness, oil film temperature rise, and friction coefficient under various finishing surfaces were compared and analyzed. Experimental results indicate that barrel finishing can simultaneously improve various parameters, such as surface roughness, texture aspect ratio, and compressive residual stress. Finishing processes can effectively reduce surface roughness, improve lubrication performance and reduce the risk of scuffing failure. This approach provided an effective method for the comprehensive evaluation of the effects of various finishing processes. The developed program offers theoretical guidance and data support for the selection and optimization design of gear surface finishing processes.

Surface integrity characterization of third-generation nickel-based single crystal blade tenons after ultrasonic vibration-assisted grinding

Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance. However, the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism, thereby limiting the study of component performance. With increasing demands for high-quality machined workpieces in aerospace industry applications, researchers from academia and industry are increasingly focusing on post-machining surface characterization. The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons, and the obtained tenons were characterized for surface integrity elements under various operating conditions. Results revealed that ultrasonic vibration-assisted grinding (UVAG) led to multiple superpositions of abrasive grain trajectories, causing reduced surface roughness (an average reduction of approximately 29.6%) compared with conventional grinding. After examining the subsurface layer of UVAG using transmission electron microscopy, the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate. This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34 μm, followed by a sub-microcrystalline grain-forming zone spanning 0.6 μm and finally, a constituent phase-twisted distorted deformation zone over 0.62 μm. Under normal grinding conditions, the tenon exhibited low surface hardening (not exceeding 15%), and residual compressive stresses were observed on its surface. In cases where grinding burns occurred, a white layer appeared on the tenon’s surface, which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects. Additionally, these burns introduced residual tensile stresses on the tenon’s surface, potentially substantially affecting its fatigue life. This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing single-crystal turbine blades for next-generation aero-turbine engines.

Surface integrity characterization of third-generation nickel-based single crystal blade tenons after ultrasonic vibration-assisted grinding

Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance. However, the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism, thereby limiting the study of component performance. With increasing demands for high-quality machined workpieces in aerospace industry applications, researchers from academia and industry are increasingly focusing on post-machining surface characterization. The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons, and the obtained tenons were characterized for surface integrity elements under various operating conditions. Results revealed that ultrasonic vibration-assisted grinding (UVAG) led to multiple superpositions of abrasive grain trajectories, causing reduced surface roughness (an average reduction of approximately 29.6%) compared with conventional grinding. After examining the subsurface layer of UVAG using transmission electron microscopy, the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate. This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34 μm, followed by a sub-microcrystalline grain-forming zone spanning 0.6 μm and finally, a constituent phase-twisted distorted deformation zone over 0.62 μm. Under normal grinding conditions, the tenon exhibited low surface hardening (not exceeding 15%), and residual compressive stresses were observed on its surface. In cases where grinding burns occurred, a white layer appeared on the tenon’s surface, which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects. Additionally, these burns introduced residual tensile stresses on the tenon’s surface, potentially substantially affecting its fatigue life. This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing single-crystal turbine blades for next-generation aero-turbine engines.

Effect of machined surface integrity on fatigue resistance of aluminum-silicon alloy ZL109

In this paper, the fatigue resistance of aluminum-silicon (Al-Si) alloy specimens obtained by single-step feed forward cutting (PZ), step-by-step feed forward cutting (FZ) and step-by-step forward-reverse finish cutting (FZF) was investigated based on the characterization of surface integrity (roughness, residual stress, microhardness), using a combination of turning experiments, surface integrity analysis and fatigue performance analysis. The fatigue life of the specimens was tested at room temperature and high cycle under the three machining processes, and an empirical model of the fatigue life was established and analyzed for the fatigue fracture morphology. The results showed that the fatigue life of the specimens can be improved by changing the surface integrity such as increasing the microhardness, reducing the surface roughness, and increasing the surface residual compressive stress. Compared with PZ, the fatigue life of FZ and FZF samples increased by 61.8 % and 64.1 % respectively. And it is obtained by analyzing experimental result and fatigue fractures that the relatively poor surface topography (i.e., the larger surface roughness) could induce stress concentration and accelerate fatigue crack initiation, the compressive residual stress mainly inhibited the crack propagation process to improve fatigue strength, and the work hardening could restrain the initiation of fatigue cracks.

Tribologic behavior and surface integrity of NAB bronze coatings reinforced with WC and Cr3C2 carbides using ytterbium fiber laser

Nickel-aluminum bronzes (NAB) are widely used in different applications due to their high mechanical properties and operational characteristics. These properties can be further improved using different finishing processes. This paper’s objective involves the wear and surface integrity characterization of CuAl7Ni6P bronze coatings formed firstly by plasma spraying and then by laser alloying with WC and Cr3C2 carbides. The YLR-2000 fiber ytterbium laser was used for laser processing and the effect of process conditions, namely a laser spot speed (LSS) and a square of the laser spot (SLS)was studied under 500 N and 1000 N loads. It was revealed that processing parameters do not have a significant effect on microhardness and friction process factors, but have significant effect on carbide alloying results. Under load of 500 N wear rates have an advantage up to 5–6 times regardless of the processing parameters and the type of reinforcing particulates. Under load of 1000 N alloying advantage is very high: 15–20 times using Cr3C2, and even 30–50 times using WC compared with results obtained for plasma spraying. These results are very important when choosing NAB laser processing input parameters in industrial applications.

Competitive effect of residual stress and surface roughness on the fatigue life of shot peened S42200 steel at room and elevated temperature

The effect of shot peening (SP) on the fatigue life of S42200 steel at room and elevated temperature is investigated. The fatigue test is carried out on a high temperature rotating bending tester. Surface integrity characterization is used to study the effect of SP on surface properties. Furthermore, Finite Element Method (FEM) combined with a fatigue damage model, namely Zheng Equation, is proposed to predict the fatigue life. The results show that SP effectively improves the fatigue life of S42200 steel under all temperatures. However, at lower temperature, higher strength SP leads to higher fatigue resistance, while at higher temperature, lower strength SP leads to higher fatigue resistance. This can be explained by the competitive effect of surface roughness and compressive residual stress (CRS) relaxation on the local stress concentration. This research can be a good guide to the application of SP at different temperatures.

Post processing of additively manufactured 316L stainless steel by multi-jet polishing method

Post-process finishing of the additively manufactured (AMed) surfaces is still a critical issue, especially for the AMed surfaces with complex surface geometry, which largely limits the application of additive manufacturing. Hence, this paper presents a multi-jet polishing (MJP) method for post processing of AMed surfaces, utilizing a number of pressurized micro/nanometer abrasive water jets. A group of systematic polishing tests are conducted on 316L stainless steel (SS) prepared by powder bed fusion, to test the polishing performance, as well as the effect of key parameters. Moreover, surface integrity characterization and analysis are also carried out to make full evaluation of the MJP process on AMed 316L SS. The results indicate that MJP is effective for the post processing of AMed 316L SS, to obtain nanometric surface roughness on AMed surfaces, shedding the light on wide application of MJP for AMed complex surfaces.

Surface Integrity Characterization by Barkhausen Noise Measurement after Milling Processes with End Mills

In aerospace industry, safety-relevant parts are subject to strict testing guidelines to guarantee part functionality. Depending on the manufacturing process, the surface integrity of the part can be modified undesirably. In addition to common rim zone analyses, such as nital etching or X-ray diffractometry, Barkhausen noise measurement offers new potentials for a non-destructive surface integrity inspection. In this work, the influence of a 5-axis gear end milling process on the rim zone was investigated. A stable correlation between Barkhausen noise and material hardness and residual stress was determined.

Investigations of the effects of combination treatments on the fretting fatigue resistance of GH4169 superalloy at an elevated temperature

In this work, a novel combination treatment was investigated as a means to improve the rotating bending fretting fatigue resistance of GH4169 superalloy at 650 °C. The properties, morphologies and composition were studied for magnetron-sputtered WS2/Ti films on substrates with and without a shot peening pre-treatment. The surface integrity and fretting fatigue performances at 650 °C were tested and compared for untreated, shot peened and combinedly treated specimens. The experimental results evidenced the significant role of shot peening pre-treatment in the adhesion behavior of oxidized films at elevated temperature. Furthermore, shot peening and magnetron sputtering were expected to have a synergistic effect to improve fretting fatigue resistance at elevated temperature. According to the surface integrity characterization and fretting fatigue tests, the surface hardened layer and the compressive residual stress fields induced by shot peening improved the fretting fatigue limit by 29%, and the average life was 12.4 times as that of the untreated specimens when the fatigue load was 600 MPa. The positive effect was attributed to the resistance properties during the initial adhesive wear stage, reduction of crack initiation and propagation and probable formation of a third body layer. Moreover, the films further increased the fretting fatigue life by 1.6 times compared with that of the shot peened specimens. The effectiveness of shot peening was retained, and the additional lubrication effect facilitated a more stable third body layer, which resulted in a longer fretting fatigue life.

Effect of Surface Integrity on Hot Fatigue Life of Ti2AlNb Intermetallic Alloy.

The effect of surface integrity on the hot fatigue performance of Ti2AlNb alloy was investigated. A turning process was used to prepare the standard specimens for hot fatigue tests. The surface integrity characterization and axial fatigue tests were performed. The results show that the influence of surface roughness on the hot fatigue performance of the Ti2AlNb alloy is a secondary factor. The compressive residual stress and enhanced microhardness in the surface layer has a significant effect on the hot fatigue life and they are dominant in the hot fatigue behavior of the Ti2AlNb alloy. Through the investigation on the characteristics of the fatigue fractures, the fatigue propagation process was significantly suppressed because of the strong residual compressive stress and microhardness distribution on the surface layer of the Ti2AlNb specimen.

Effects of Machined Surface Integrity on High-Temperature Low-Cycle Fatigue Life and Process Parameters Optimization of Turning Superalloy Inconel 718

Machined surface integrity characteristics, including surface stresses, physical-mechanical properties and metallographic structures, play important roles in the fatigue performance of machined components. This work aimed at investigating the effects of machined surface integrity on high-temperature low-cycle fatigue life. The process parameters were optimized to obtain required surface integrity and fatigue life of the turning superalloy Inconel 718. The relationships between low-cycle fatigue life and machined surface integrity characterization parameters were established based on the low-cycle fatigue tests at a high temperature (650 °C). The sensitivities of turning process parameters to high-temperature low-cycle fatigue life were analyzed, and the optimization parameters were proposed with the goal of antifatigue manufacturing. Experimental results indicated that the impact order of the characterization parameters of machined surface integrity on the high-temperature low-cycle fatigue life were the degree of work hardening RHV, the residual stress in the cutting speed direction S22, the fatigue stress concentration factor Kf, the degree of grain refinement RD and the residual stress in the feed direction S33. In the range of turning parameters of the experiments in this research, the cutting speeds could be 80~110 m/min, and the feed rate could be 0.10~0.12 mm/rev to achieve a longer high-temperature low-cycle fatigue life. The results can be used for guiding the fatigue-resistant manufacturing research of aeroengine superalloy turbine disks.

Multi-scale characterization of material and surface integrity of Inconel 718 when milling by Abrasive Water Jet process: Context of repair application

Inconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting poor machinability and used in the hot section of aircraft engines. These components are subjected to severe thermo-mechanical loads in a highly corrosive environment, limiting their service life due to cracks and wear. Due to their high added-value, repair of damaged IN718 components is an interesting alternative instead their replacement. Repair process involves material removal of the damaged zone and subsequent cavity refill. Nevertheless, material removal of IN718 by conventional methods is a challenging task. Abrasive Water Jet (AWJ), a non-conventional machining process, offers a potential alternative to mitigate IN718 machining problems. However, research on the impact of AWJ process parameters during IN718 milling on the surface and material integrity is limited in the literature. Furthermore, in repair context, no study proposes AWJ machining as material removal process. The present work focuses on a multi-scale characterization of the influence of AWJ process parameters (pressure, traverse speed, step-over distance and abrasive size) on surface roughness, depth of cut, abrasive embedment and residual stress, during milling of untreated IN718. Surface integrity characterization on the milled surfaces was conducted through 3D optical microscopy, profilometry and SEM techniques. Residual stress measurements were performed in longitudinal and transverse directions with respect to the machining path using XRD technique. The results showed that all milled surfaces presented abrasive embedment and a compressive residual stress state with similar values in both directions. Up to 15% of the area of a milled surface consisted of abrasive embedment. The tool path has not influenced the residual stresses. Furthermore, surface roughness is dependent on pressure and traverse speed; depth of cut is influenced by pressure, traverse speed and grit size; abrasive embedment depends on pressure, step-over distance and grit size; whilst, residual stresses are influenced by traverse speed and grit size.

A novel hole cold-expansion method and its effect on surface integrity of nickel-based superalloy

Preferred surface integrity around the hole wall is one of the key parameters to ensure the optimized performance of hole components for nickel-based superalloy. The novel hole cold expansion technique introduced in this work involves the laser texturing process (LTP) followed by the Hertz contact rotary expansion process (HCREP), where the cylindrical sleeve is the critical component connecting the above-mentioned two processes. The purpose of LTP is to obtain the most optimized strengthened cylindrical sleeve surface, preparing for the following HCREP. Hereafter, the HCREP acts on the nickel-based hole components by the rotary extruding movements of the strengthened sleeve and conical mandrel tools. As compared to the as-received GH4169 material, the surface integrity characterization for the strengthened hole shows that a plastic deformation layer with finer grains, higher micro-hardness, deeper compressive residual stress (CRS) distribution and lower surface roughness is formed at the hole wall. In addition, transmission electron microscope (TEM) observations reveal the microstructure evolution mechanism in the strengthened hole. Grain refinement near the hole wall is regarded as the fundamental reason for improving the surface integrity, where the aggregated dislocations and recombined dislocation walls can be clearly observed.

Surface Integrity Assessment Upon Electric Discharge Machining of Die Steel Using Non-Destructive Magnetic Barkhausen Noise Technique

Surface integrity characterization of manufactured component is very important as it significantly affects the in-service performance of the component. Till now, surface integrity was evaluated using conventional measurement technique like microhardness tester, X-ray diffraction, optical microscopy and surface roughness tester. But, this technique being laboratory based cannot be used for in-service monitoring of the surface integrity. The present study focuses on the characterization of surface integrity upon electric discharge machined sample using non-destructive magnetic Barkhausen noise technique. Electric discharge machining was performed in die-sinking mode on die steel using copper–tungsten electrode (negative polarity). Experiment was performed by selecting different levels of peak current, gap voltage and pulse on time. Surface integrity characteristics like microhardness change, residual stress, microstructural alteration and surface roughness were analysed using microhardness tester, X-ray diffraction, optical microscopy and surface roughness tester, respectively, and were then correlated with magnetic parameter like root mean square value and peak value obtained from Barkhausen noise signal. The results show a good correlation between magnetic parameter (RMS and Peak value) of Barkhausen noise with the microhardness and surface roughness of the machined sample.

Machinability and Surface Integrity Characterization in Hard Turning of AISI 4320 Bearing Steel Using Different CBN Inserts

The thermomechanical interaction between the cutting tool and the workpiece in any material removal process is a key factor in defining the efficiency and productivity of the process. It is especially important in cutting hard-to-machine materials such as titanium- and nickel-based alloys or hardened steels. The productivity of the process can be defined in terms of machining time, intervals of tool change (due to tool wear) and surface integrity characteristics such as dimensional tolerances, surface roughness and the machining-affected zone. The objective of this work is to conduct a comprehensive study of the performance of three different industrial-grade CBN cutting inserts during hard turning of AISI 4320 case-carburized steel. The CBN inserts all had the same geometry but used different edge preparation and coating technologies. To quantify tool performance, the cutting forces and tool wear were measured at consistent intervals and the surface integrity of the workpiece was characterized in terms of surface roughness, white and dark layer depths, micro-hardness and residual stresses. Results show that the stability of the cutting edge on two of the tested inserts plays an important role in determining tool life (where 60% higher tool life was achieved compared to the other tested insert with unstable cutting edge), cutting force stability and the formation of compressive residual stresses on the surface of the turned workpiece

Surface integrity characterization of austenitic, martensitic and ferritic stainless steel under different grinding process

Grinding is the final process in the manufacturing of precise components with adequate surface integrity. Surface integrity has significant effect on the working life of component. The aim of the present work is to experimentally investigate the effect of eco-friendly grinding i.e. dry, belt and pedestal grinding on the surface integrity of different stainless steels (SS) like austenitic AISI 304SS, martensitic AISI 410SS, and ferritic AISI 430SS. Surface integrity was assessed by surface topography, surface roughness, microchip morphology, metallographic of microchip and thermal damage of ground surface. The surface topography of microchip and ground samples was observed by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDX). Grinding performance was investigated in terms of grinding force. Further, corrosion performance of different grade SS was measured using potentiodynamic corrosion test in 0.9N NaCl solution under different grinding condition. The result shows that excellent ground surface quality with lowest surface roughness was obtained in AISI 304SS under all grinding modes. Spherical and ribbon microchips were observed during belt and pedestal grinding. SEM-EDX analysis indicated that iron-chromium oxide nodules were formed on ground surface and microchip. Lower grinding force was obtained during dry grinding of AISI 430SS. Finally, maximum corrosion rate was found in all grades of stainless steel during pedestal grinding owing to rupture of Cr2O3 protective layer.

Characterization of Surface Integrity of Ti6Al4V Alloy Machined by Using Wire Electrical Discharge Machining Process

The material Ti6Al4V is the alpha plus beta phase titanium alloy with great strength, low weight ratio and excellent resistance to corrosion and chemicals. In the present study, cutting of Ti6Al4V material has been performed by utilizing wire electrical discharge machining process with the different set of machining parameters and observed the response parameters. Surface integrity of machined specimens, including surface morphology, height feature, surface roughness and root mean square roughness has been evaluated empirically. Atomic force microscopy has been employed for measuring the surface integrity of machined pieces. It has been found that Ti6Al4V alloy possesses excellent surface characteristics after wire electrical discharge machining

Surface integrity characterization of ground hardened H13 hot die steel using different lubrication environments

Surface integrity has a significant effect on the service life of manufactured component as poor surface integrity may cause failure of produced component during its service life. Grinding is the last processing operation during manufacturing cycle of components, which decides the surface integrity of manufactured component. Surface quality of a component depends on the lubricating and cooling effect of cutting fluids during grinding. Thus, the present research work focused on an experimental study the effect of different lubrication modes like dry, flood, minimum quantity lubrication (MQL) on the surface properties of ground hardened H13 hot die steel. Surface integrity was evaluated in terms of surface roughness and microhardness of ground surface, ground surface topography, and microchip morphology. Whereas, grinding performance was evaluated in terms of grinding force. The surface topography and elemental composition of ground surface along with microchip were observed using scanning electron microscope (SEM), atomic force microscope (AFM), and energy dispersive x-ray spectroscopy (EDX). Experimental results indicated that MQL with castor oil (CO) provided lowest surface roughness and grinding forces among all lubrication conditions, which were Ra: 0.245 μm, Rz: 1.846 μm, Ft: 30.65 N, and Fn: 42.35 N, respectively. According to AFM analysis, poor surface quality (deep grooves and furrows) was observed under dry grinding due to micro-fractured abrasive grains and hard microchip rubbed over the ground surface. Continuous and smooth (no wear track) microchip was observed with MQL-CO lubrication. Further, EDX analysis indicated that microchips obtained upon MQL-CO lubrication were having very less carbon peaks without any surface oxidation. Higher microhardness was observed with MQL-DIW cooling due to suddenly quenching effect over the nascent ground surface.

Surface Integrity Analisys in the Hard Turning of Cemented Steel AISI 4317

This work was based on the surface integrity analysis of hardened steel, AISI 4317 case carburized, quenched and tempered with 58 HRC, obtained by a turning operation executed with CBN (cubic boron nitride) tool, varying three basic cutting parameters (cutting speed, feed rate and cutting depth). The surface integrity characterization was conducted analyzing the behavior of the surface roughness Ra, residual stresses and with layer presence after turning. Also, the cutting forces were measured. The experimental planning used was a central composite design. The results and data were statistically treated by the Statistica software, enabling the generation of a mathematical model, relating the dependent variables with the independent variables. The roughness values Ra obtained after the experiments ranged from 0.31 to 2.8 µm, providing an indication that is possible to replace grinding process by hard turning using CBN tools that could reduce machining time and costs. The hard turning process generated compressive residual stresses profiles and white layer formation, from 1.1 to 5.1 µm, on the surface of the samples. The penetration force showed the highest values for the turning forces measurements. The lowest values for the cutting parameters represented the optimized surface integrity of the AISI 4317 steel.

Experimental study on surface integrity of cryogenically machined Ti-6Al-4V alloy for biomedical devices

Titanium and its alloys are widely used in the biomedical sector. In this field, titanium and its alloys are the material of choice for biomedical devices such as hip and knee replacements. Usually, a Total Hip Replacement (THR) is based on four components, made out of different materials due to the material properties associated with the functional performance. One approach to lower the overall manufacturing costs and enhance the reliability of THR’s is to manufacture the prosthesis out of one material. The titanium alloy Ti-6Al-4V is, therefore, feasible as it exhibits better osseous integration compared to other metallic materials used as orthopedic devices. The sole use of Ti-6Al-4V alloy requires improvements of surface integrity (SI) and characteristics that are sensitive to SI. One possible way to improve the tribological properties of the THR and the biocompatibility of Ti-6Al-4V alloy is to deliberately decrease the material grain size in the surface layer from the micron scale (> 1 µm) to the region of nano-sized grains (< 100 nm).The objective of this paper is to study and prove the formation of nano-sized grains within the surface as well as the characterization of surface integrity when machining Ti-6Al-4V alloy. Therefore, different cryogenic cooling strategies are used where liquid nitrogen (LN2) is applied to the flank and rake face, and just to the flank face respectively. To compare the effect of cryogenic machining, conventional flood cooling was applied as third cooling strategy. As cutting tool, a roughing tool, having a large cutting edge radius, was used, since severe plastic deformation (SPD) has shown to be capable to produce nano-sized grains in the surface. The results showed, that cryogenic machining using a large cutting edge radius tool is able to decrease the materials grain size to the region of nano-sized grains.