Surface Integrity Evolution Research Articles

Modeling and analysis of surface integrity transition in cutting of Sip/Al composites based on coordination deformation effect of particle-matrix

With the wide application of Sip/Al composites in key fields, it is critical to understand the material removal behavior and surface integrity evolution mechanism of Sip/Al composites. In this paper, based on the nanoindentation and scratching experiments, the coordination deformation behavior of Si particles and the Al matrix were investigated at the micro-scale, and the mechanism and conditions of surface integrity transition (SIT) of Sip/Al composites were elucidated. Then, taking into account the feature of particle fragmentation and detachment caused by interfacial failure, an analytical model of specific cutting energy for Sip/Al composites cutting under different material removal modes was established. The competitive relationship between ductile deformation and surface defect formation was investigated, and a quantitative prediction model for the critical depth of SIT was proposed. The results show that the evolution of the material removal behavior of Sip/Al composites is a consequence of the coordination deformation the Al matrix and Si particles. The material removal mode of Sip/Al composites transitions from ductile removal to quasi-brittle removal with particle fragmentation and detachment, and there is an obvious SIT characteristic. The prediction results of critical depth are in agreement with the experimental results, with an average error of less than 9.8 %. Moreover, an appropriate increase in cutting speed can effectively enhance the surface integrity of Sip/Al composites. This research contributes to a deeper understanding of the low-damage machining mechanism of Sip/Al composites.

Surface Integrity Evolution in Grinding by means of In-Process Eddy Current Inspections

The in-process detection of grinding burns has earned considerable interest from both researchers and industries in recent years. Various Non-destructive testing (NDT) technologies, including Eddy Current (EC), Barkhausen Noise (BN), and Acoustic Emission sensors (AE), have been employed to address this issue, yielding successful results for specific applications. However, a comprehensive understanding of burn generation and its prevention in grinding operations remains an area of interest that has not yet been fully resolved.This paper focuses on investigating the electromagnetic response of a custom-made EC sensor applied to UNE F-522 (AISI 01) steel during in-process inspections. Experimental grinding tests have been performed using a special EC inspection head installed in the grinding machine. The impedance change of the material during grinding is discussed in terms of the machine out-puts (Power consumption) and other grinding variables, such as number of passes, the roughing stock removal, and the finishing strategy. The experimental results demonstrate that the proposed EC technology not only enables the detection of burns, but also enhances comprehension of the surface integrity changes occurring during the grinding process.

Effects of rare earth addition and service mode on surface integrity evolution of high-end machine tool spindle bearings under service

Machine tool spindle bearings used as supporting rotator parts play a very important role in machining industry. Keeping a good surface integrity is crucial to the long-time and high-efficiency work of the bearings. To find out the crucial factors for bearing failure, surface integrity evolutions on machine tool spindle bearings made from a normal bearing steel and a newly developed rare-earth-addition bearing steel were compared after benchtop tests in this work. Furthermore, surface integrity evolutions on bearings were analyzed under field service with more complex service conditions. The results show that the surface integrity changes under both benchtop testing and filed service, while the surface damages and changes in surface integrity on the inner rings are more significant than those on the outer rings. Meanwhile, the surface damage modes are mainly scratches and impressions on the benchtop bearings, while surface rolling contact fatigue predominates the damages on the field bearings. Furthermore, the addition of rare earth elements in bearing steels transfers the crack initiation mode from inclusion initiated to martensite initiated under service, possibly resulting in a higher stability of accuracy and longer life for bearings.

Evolution of cold-expanded microstructure with aging temperature and its influence on fatigue performance of hole structure at elevated temperature

A surface-strengthened layer formed by cold expansion (CX) evolves at high temperatures. The evolution of surface integrity and microstructure after a CX-treated superalloy GH4169 center hole plate was investigated in the present study. Aging at 400 ℃ and 600 ℃ took place with a duration of 500 h (CX400 and CX600). In addition, the fatigue properties at 820 MPa/600 ℃/R= 0.1 were investigated. The results show that CX has a smooth surface, a compressive residual stress field with a depth of more than 1.4 mm and a non-improved surface hardness. The statistical fatigue life of the as-received specimens was 7015 cycles, and the fatigue lives after CX and CX400 treatment were 5.27 and 2.86 times higher, respectively, indicating an increase by CX and a decrease by 400 ℃ aging. In contrast, the fatigue life of the original sample decreased to 5576 cycles with 600 ℃ aging, while the corresponding fatigue life of the CX600-treated sample was 7979 cycles, representing a significant decrease in both cases. The transformation of the main strengthening γ″ phase to the δ-phase upon aging at 600 ℃/500 h are the main reasons for the weakening of the fatigue properties, which did not occur upon aging at 400 ℃ (see TEM).

Comprehensive experimental study of shot peening on the surface integrity evolution of 12Cr2Ni4A high-strength steel

Comprehensive experimental study of shot peening on the surface integrity evolution of 12Cr2Ni4A high-strength steel

Effect of laser shock peening on boring hole surface integrity and conformal contact fretting fatigue life of Ti-6Al-4 V alloy

The service performance of hole surface is directly tied to its machining-induced surface integrity which is usually produced by sequential operations. Due to its conformal geometry, the assembly hole has a high risk of fretting damage when connecting parts. This paper investigated the effect of laser shock peening on the surface integrity of boring hole and fretting fatigue life of Ti-6Al-4 V alloy. The results showed that the fretting fatigue life of the specimens was dramatically improved at various fatigue stress levels after LSP. The fretting fatigue life was respectively increased by 14 %, 2.27, and 9.35 folds at fatigue stress levels of high (800 MPa), intermediate (500 MPa), and low (300 MPa). In addition, the fatigue stress limit was increased by 70.4 % at the fatigue cycle of 1.0 × 107. The improvement was resulted from the beneficial surface integrity which inhibited fretting wear, and decreased short crack growth rate. Besides, the LSP could not necessarily introduce a greater compressive residual stress (CRS) but should certainly increase the penetration depth of the CRS. The LSP process partially relaxed the CRS depending on whether the existed surface residual stress reached a certain threshold, which was –450 MPa under the selected conditions in this study. This research helps understand the surface integrity evolution in successive processing, which may contribute to planning appropriate processes for desirable surface integrity.

Evolution of hole surface integrity in successive processing using sequential milling and laser shock peening

Part's surfaces are usually produced by successive/integration machining process and the performance of the part is directly tied to the generated surface integrity. Holes are commonly used in many critical engineering structures to connect parts, whose surface primarily characterizes a high risk of fretting or contact fatigue failure. In this paper, the evolution of metallurgical and mechanical surface integrity of Ti-6Al-4V alloy hole surface which machined using multi-step milling and successive laser shock peening (LSP) treatment was investigated. Firstly, a special workpiece with various hole surface pieces was designed and four different sequential milling processes were set to conduct the milling experiments. A comprehensive analysis of the evolution of surface roughness, microstructure, microhardness, and residual stress along the sequential processing steps was carried out. The results showed that the forms of surface integrity evolution could be classified into mono-evolution and coupling evolution, which were correlated to the combined effect of the milling parameters, cutter-workpiece engagement nature, milling sequence, milling mode, and the coolant/lubricant applied strategy. Mono-evolution was predominated in material removal sequences (milling sequences), while the coupling evolution was dependent on the radial depth of cut (DoC, ~50 μm). By comparison, coupling evolution was prominent in non-material removal related sequences (LSP treatment). Due to the conformal contact nature of tool-workpiece engagement and the flood cooling strategy, the microhardness in the subsurface layer was not significantly altered in milling sequences, except that the up-milling normally produced a surface with lower hardness and the down-milling produced almost unchanged surface hardness compared with bulk material. The residual stress was a result of the coupling effect of the residual stress field introduced in the previous and current machining sequences, whose in-depth distribution could be represented as an exponential decay function. The degree of influence of the machining sequences and their interactions on the final residual stresses could be evaluated by utilizing a set of weighting coefficients. This research indicated that understanding the effect of successive processing on the surface integrity evolution could help in planning of appropriate processes to achieve desirable surface integrity.

A plastic strain energy method exploration between machined surface integrity evolution and torsion fatigue behaviour of low alloy steel

To explore the evolution mechanism of multistage machining processes and torsional fatigue behaviour based on strain energy for the first time and provide process optimization of axis parts of low alloy steel for service performance, four multistage machining processes were applied to the 45CrNiMoVA steel, including the Rough Turning process (RT), RT+ the Finish Turning process (FRT), FRT+ the Grinding process (GFRT) and RT+ the Finish Turning process on dry cutting condition (FRT0). The result showed that the FRT process’s average low-cycle torsional fatigue life increased by 50% when it evolved from the RT process. The lower surface roughness of Ra 1.3 μm caused the total strain energy to increase by 163.8 Pa mm/mm instead of the unchanged strain energy density, and the crack feature evolved from some specific bulges to flat shear plane characteristics. When the GFRT process evolved from the FRT process, its average fatigue life increased by 1.45 times, compared with the RT process. Plastic strain amplitude decreased by 21%, and the strain energy density decreased by 4% due to more considerable compressive residual stress (−249 MPa). Plastic deformation layer depth had a consistent tendency with surface roughness. In this paper, surface integrity evolutions on cyclic characteristics and fatigue behaviour have also been explained. A fatigue life prediction model based on the energy method for machined surface integrity is proposed.

Surface integrity evolution of a Ni-based single crystal superalloy by laser shock peening

The single crystal superalloy SRR99 experimental samples were single point treated by laser shock peening (LSP) with laser pulse energy of 5–7 J. The surface morphology, micro-hardness, surface residual stress and surface microstructure of samples prior and after LSP were determined by corresponding characterization instrument. From the surface morphology, a circular pit was formed in surface, which due to the severe plastic deformation induced by LSP, and the diameter & maximum relative height of circular pit were increase with laser pulse energy. From the micro-hardness and residual stress test results of samples, these were increased after LSP treatment. In detail, the initial microhardness and residual stress were 398 HV and -498 MPa, with laser pulse energy of 5 J, the microhardness and residual stress were increased to 455 HV and -843 MPa, when the laser pulse energy was increased to 7 J, the microhardness and residual stress were increased to 512 HV and -942 MPa. In addition, the surface roughness of samples was increased too, which reflect the severe plastic deformation. By observing the microscopic morphology of the bottom of the pit, it is found that there are convex structure and crater shape defect structures on the bottom surface, and the formation of these structures may affect the surface roughness of the shock area. Although LSP caused certain degree of twist deformation of the shape of the γ' phase, the original strengthening method characteristics of the matrix phase and strengthening phase was not destroyed, which still maintained the creep strength and thermal fatigue properties of superalloy. The experiment show that LSP can cause significant work hardening effect on the surface of superalloy, and the generated high residual compressive stress can effectively delay the initiation and propagation of cracks. Therefore, LSP technology can effectively improve the fatigue life of single crystal blade components.

Surface integrity evolution of Nb-Ti microalloyed steels along the gear manufacturing chain

The increasing demand for high performance gears requires in-depth investigations of alternative materials to those commonly used. In this respect, microalloyed steels may appear as an alternative with technical and economic potential. Microalloyed steels may exhibit a more refined grain structure than conventional steels, which is commonly induced by the precipitation of highly stable and dispersed second-phase particles. This investigation aimed at understanding how the steel grain structure obtained by the addition of niobium (Nb) and titanium (Ti) as microalloying elements correlates to the material surface integrity promoted by a conventional gear manufacturing chain. The results indicated that the addition of microalloying elements leads to a refined and homogeneous grain structure. The residual stress state also proved to be both more compressive and homogeneous and the roughness exhibited greater stability. Such characteristics place the microalloyed steels in a prominent position regarding their application in the gear manufacturing, indicating the possibility of fatigue lifetime improvement.

Process parameter optimization and surface integrity evolution in the high-speed grinding of TiAl intermetallics based on grey relational analysis method

Process parameter optimization and surface integrity evolution in the high-speed grinding of TiAl intermetallics based on grey relational analysis method

Surface integrity evolution and wear evolution of the micro-blasted coated tool in high-speed turning of Ti6Al4V

The coated tool is one of the most widely used cutters in the processing of titanium alloy. The wear of the coated tool is influenced by its surface integrity which can be improved by surface treatment, such as micro-blasting. The experiment of high-speed dry turning of titanium alloy Ti6Al4V (TC4) is carried out by the PVD-TiAlN coated carbide tools which are untreated and micro-blasted. For the coated tool, the evolution of the tool surface integrity, including tool surface roughness, tool surface topography, tool surface hardness, and tool surface residual stress, is studied at different wear stages. Moreover, the evolution of tool wear is analyzed at different wear stages. Then, the influence of tool surface integrity on tool wear is investigated. It is suggested that the tool surface integrity and wear resistance of the treated tool is improved. The change of tool wear is consistent with the change of coating surface integrity. That is to say, the better tool surface integrity is, the less tool wear will be. In addition, the main tool wear mechanisms are adhesive wear and oxidative wear. In the end, the stable wear stage of treated tools is prolonged, and the tool life is increased by more than 40%.

Surface integrity evolution of machined NiTi shape memory alloys after turning process

Owing to their shape memory effect and pseudoelasticity, NiTi shape memory alloys (SMAs) are widely used as functional materials. Mechanical processes particularly influence the final formation of the product owing to thermal softening and work-hardening effects. Surface integrity is an intermediate bridge between the machining parameter and performance of the product. In this study, experiments were carried out on turning NiTi SMAs at different cutting speeds, where surface integrity characteristics were analyzed. The results show that a higher cutting speed of 125 m/min is required to turn NiTi SMAs based on the evaluation of surface integrity. The degree of work hardening is higher at 15 m/min. Consequently, as a primary effect, work hardening appears on the plastic deformation of the machined samples, leading to dislocations and defects. As the cutting speed increases, the thermal softening effect exceeds work hardening and creates a smoother surface. A stress-induced martensitic transformation is considered during the turning process, but this transformation is reversed to an austenite from the X-ray diffraction (XRD) results. According to the differential scanning calorimetry (DSC) curves, the phase state and phase transformation are less influenced by machining. Subsequently, the functional properties of NiTi-SMAs are less affected by machining.

Investigation of surface integrity in laser-assisted machining of nickel based superalloy

While laser-assisted machining can significantly improve the machinability of nickel-based superalloy, the mechanism of surface integrity evolution and its influence on the material functional performance is still not clear. The present study gives a comprehensive investigation on the surface integrity of laser-assisted milling (LAMill) process with an in-depth study of the mechanism of chip formation, microstructural and mechanical alternations, supported by key outcomes from the two constitutive processes, conventional milling (CMill) and single laser scanning (LS). Although the high thermal affected layer in LAMill process has been removed through the cutting chips, a significant bending effect has been found in both the LAMill and LS workpiece. More interestingly, a combined impact of the residual stress from LS and CMill has been found on LAMill workpiece while a lattice evolution has been revealed regarding both the thermal and mechanical influence. Specifically, inadequate fatigue performance on LAMill and LS workpiece has been found due to the high thermal effect in the superficial layer regarding the residual tensile stress distribution and microstructure variation. While LAMill is generally considered as a promising machining method with improved machinability of difficult-to-cut materials, this research shows a poor workpiece functional performance (fatigue) and justifies its application prospect.

Experimental study on surface integrity of ultra-high-strength steel by ultrasonic hot rolling surface strengthening

Ultrasonic hot rolling, a newly developed technology of surface modification and multi-field strengthening, is used for surface treatment of ultra-high-strength steel (45CrNiMoVA) at different temperatures, with the temperature as high as 300 °C. Based on the thermal softening and strain rate sensitivity of ultra-high-strength steel, the formation and evolution of surface integrity including surface topography, residual stress and microstructure were analyzed after ultrasonic hot rolling. It is found that ultrasonic hot rolling can still achieve good surface finishing effect, in which rolling pressure and ultrasonic impact play a key role. The residual stress amplitude and the depth of the affected layer are larger under the ultrasonic hot rolling, which is the influence of the ultrasonic impact and the thermal field together. In the temperature range of 150 °C–200 °C, the surface integrity after ultrasonic hot rolling is the best. The reason for the more stable residual stress after ultrasonic hot rolling is work hardening, age hardening, and precipitation hardening.

Evolution of surface integrity and fatigue properties after milling, polishing, and shot peening of TC17 alloy blades

The surface integrity and fatigue properties of TC17 alloy blades under integrated manufacturing processes are investigated. The Ra values of milling–polishing (MP)-processed and milling–polishing–shot peening–vibration polishing (MPSV)-processed blades are less than 0.4 µm. MPSV produces a strengthened layer about 100 µm and a gradient microstructure. The modal analysis results obtained from finite element calculation corresponds well with the values measured experimentally. The fatigue lives of the MPSV-processed blades are increased by approximately 119.5% compared with the MP-processed blades. The fatigue fracture morphology indicates that fatigue cracks are initiated on the leading edge surface regardless of the processes employed.

Surface modification through combination of finish turning with low plasticity burnishing and its effect on fatigue performance for Inconel 718

The machining of Inconel 718 with high surface integrity and long fatigue life is a challenging work in aero-industry due to their difficult-to-cut properties. Both the surface integrity and service performance for machined Inconel 718 components need further improvements. In this study, the combined finish turning (FT) and low plasticity burnishing (LPB) surface modification processes has been proposed for the sake of improving surface integrity and fatigue performance of machined Inconel 718. Firstly, the surface integrity characteristics such as surface topography, roughness, micro-hardness, phase change and principal residual stress of machined Inconel 718 through the combination of FT with LPB processes are investigated. Subsequently, the fatigue performance of machined Inconel 718 is systematically evaluated by uniaxial tension-tension fatigue tests. Finally, the effect of surface integrity evolution on fatigue performance of Inconel 718 is revealed. The fatigue life can be improved by 82.4% with the combination of FT and LPB-18 process in comparison with FT process. The improved fatigue life dependence on the decreased surface roughness and the enhanced minimum principal residual stress field can be concluded by comparing different LPB processes.

Evolution of White Layer during Wire-Cutting and Comparison of Several Methods to Improve Surface Integrity for Fineblanking Tools

Powder metallurgical high speed steel (such as S390) has superior mechanical properties and been used as fineblanking tools. The electrical discharge machining has been widely used for cutting fine blanking tools which are made of especially hard tool steels. Whereas, its thermal nature causes great concerns regarding surface integrity, which matters a lot to tool life. In the present study, the evolution of surface integrity of the S390 with multi-cutting is comprehensively compared. The result shows that the surface roughness, white layer thickness and surface residual stress decrease with the increase of cutting pass. Additionally, the effectiveness to remove white layer on HSS S390 by manual and towed polishing and electrolytic polishing are compared. At last, a device of abrasive water jet polishing is designated to remove the white layer resulted from wire-cutting.

Surface integrity evolution and fatigue evaluation after milling mode, shot-peening and polishing mode for TB6 titanium alloy

Surface integrity is closely related to the service life of parts and components. Effects of four kinds of integration processes on surface integrity and fatigue life are studied. These four integration processes are M (milling), MP (milling and polishing), MPS (milling, polishing and shot-peening), and MPSP (milling, polishing, shot-peening and polishing). When roughness, micro-hardness, residual stress, micro-structure and fatigue were considered after the four integration processes, research results show that MPSP process can obtain the best surface topography and roughness, micro-hardness, and residual stress field distribution; MPSP process has the longest fatigue life, and the fatigue life of MPSP process is about 68 times of M process, 56 times of MP process, and 48 times of MPS process; The fatigue fracture of the specimen after MPSP process is flat, and the depth of the crack initiation site for MPSP specimen is approximately 150μm below the surface.

Surface integrity evolution and machining efficiency analysis of W-EDM of nickel-based alloy

Abstract Nickel-based alloys have wide applications in many industries due to their outstanding properties. However, it is very difficult to machine using cutting and grinding methods because of their low thermal conductivity, strong strain hardening, and high strength at elevated temperatures. Electrical discharge machining is an alternative competitive process to machine Nickel-based alloys by electrical erosion. This study focuses on the evolution process of surface integrity and machining efficiency of W-EDM in machining IN 718 by one rough cut (RC) mode followed by three trim cut (TC) modes. Material removal efficiency, surface roughness, surface topography, surface alloying, and microhardness have been characterized. Results show that high material removal efficiency can be achieved in W-EDM. Six-sigma distribution of Ra in RC mode is different from that of TC modes. The high toughness of IN 718 would be the major contributing factor to the absence of microcracks in the TC modes. Microcracks just exist in the white layer. Thick white layers (6–8 μm) with microcracks in RC mode and very thin white layers (0–2 μm) free of those defects in TC2 mode can be observed, while white layer is nearly invisible in TC3 mode. The microhardness of white layer in TC mode is higher than that in MC mode.