Residual Stresses in Machining of AISI 52100 Steel under Dry and Cryogenic Conditions: A Brief Summary

17th Conference on Material Forming (ESAFORM) - FinlandResidual stress is one of the most important surface integrity parameter that can significantly affect the service performance of a mechanical component, such as: contact fatigue, corrosion resistance and part distortion. For this reason the mechanical state of both the machined surface and subsurface needs to be investigated. Residual stress induced by dry and cryogenic machining of hardened AISI 52100 steel was determined by using the X-ray diffraction technique. The objective was to evaluate the influence of the tool cutting edge geometry, workpiece hardness, cutting speed, microstructural changes and cooling conditions on the distribution of the residual stresses in the machined surface layers. The results are analysed in function of the thermal and mechanical phenomena generated during machining and their consequences on the white layer formation

INVESTIGATION OF POLISHING METHODS AND SURFACE ANALYSIS AFTER MACHINING \u3cem\u3eAISI 4140\u3c/em\u3e ALLOY STEEL

AISI 4140 alloy steel has been a very common material to be investigated in automotive and aerospace industries for several decades. AISI 4140 alloy steel is chromium, molybdenum, and manganese containing low alloy steel. It has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. The functional performance is largely determined by the surface states after machining. The aim of the present study is to explore the polishing methods and surface analysis after machining AISI 4140 alloy steel in different cutting speeds and cooling conditions. The surface analysis includes surface roughness, hardness and residual stresses. Compared to traditional polishing, an innovative experimental work was conducted on electro-polishing technology for removing surface layer before subsurface residual stress measurement. The results of this work show that the electro-polishing method is a significant approach for the residual stress analysis. High cutting speed and cooling conditions can improve the surface quality to achieve lower surface roughness, higher microhardness and more compressive residual stresses after machining AISI 4140 alloy steel

Master of Science

thesisSurface integrity plays a very important role in the life and functionality of machined surfaces used in a variety of engineering applications. Manufacturing processes and their sequence, along with the selection of cutting conditions and cutting tools, eventually dictate the type of surface that is being produced. Surface integrity is subdivided into several components, of which, some important components are surface roughness, residual stresses and subsurface microstructures. Enhanced understanding of all these factors and their interactions will potentially lead to advanced knowledge driven machining process planning. This thesis focuses on an experimental investigation of the effects of cutting tool coatings and cutting fluid application on surface integrity (residual stress, surface roughness and subsurface microstructure) in machined Ti6Al4V titanium alloy. For measuring residual stresses, the hole drilling method was used in this thesis research. The tools selected for the machining were uncoated flat-faced, uncoated grooved, multilayered (TiCN/Al2O3/TiN) CVD coated grooved, and single-layered (TiAlN) PVD coated grooved tools with tungsten carbide substrates. Three different cutting fluid application conditions were used namely: dry, minimal quantity lubrication (MQL) and flood. To illustrate the significance of this thesis, it was observed that a grooved multilayered CVD coated cutting tool under the influence of MQL condition, induced the highest near-surface residual stresses; on the other hand, the same tool, when machined under dry condition, produced the lowest residual stresses. Thus, it can be seen that a specific cutting tool material and/or geometry produce significantly different surface integrity when it is combined with different cutting fluid application conditions. Moreover, the microstructural analysis performed on these machined workpieces revealed significant changes in the subsurface microstructure with respect to the type of cutting tool-cutting fluid application combination used and correlated strongly with the measured residual stress profiles. The combined effect of the type of cutting tool along with the type of cutting fluid application condition on surface integrity is extremely significant. The results and findings o f this thesis have the potential to aid in choosing the combination of the cutting tool and the cutting fluid application that are best suited for machining. Apart from that, this thesis also provides several recommendations for future research on the fundamentals of the interactions between machining parameters such as tool coatings, tool geometry and cutting fluid applications and their significant effects on the generated surface integrity and the life of the component there after

Cutting tool wear in turning 316L stainless steel in the conditions of minimized lubrication

316L stainless steel has emerged as one of the most used material in design and manufacturing for automotive, aerospace, marine, civil nuclear to produce critical components (valves, seats, pipes etc.). Despite, their huge application, during the machining of 316L stainless steel numerous challenges arise in terms of tool wear that are very detrimental for the surface of machined part. To obtain an extended life of tool used for machining commonly 316L stainless steel two different methods of cooling based on minimum lubrication condition, namely Minimum Quantity Lubrication (MQL) method and Minimum Quantity Cooling Lubrication (MQCL) with the addition of extreme pressure and anti-wear (EP/AW) method, respectively were settled. The use of the MQL method resulted in a reduction of the cutting tool wear by approximately 9% compared to the MQCL + EP / AW method and by approximately 21% compared to dry machining. Further, the highest values of wear indices were achieved during dry machining and the lowest ones in the method of minimized lubrication which validate the minimum lubrication as beneficial for reducing the wear progress

THE INFLUENCE OF CRYOGENIC MACHINING ON SURFACE INTEGRITY AND FUNCTIONAL PERFORMANCE OF TITANIUM ALLOYS FOR BIOMEDICAL AND AEROSPACE APPLICATIONS

The excellent properties of titanium alloys such as high strength, as well as good corrosion and fatigue resistance are desirable for the biomedical and aerospace industry. However, the same properties that make titanium alloys desirable in high-performance applications also make these space-age materials “difficult-to-machine” materials, as the titanium alloys exhibit high cutting temperatures because of their high strength and low thermal conductivity. Cryogenic machining is a severe plastic deformation (SPD) processes which uses liquid nitrogen as the coolant to take away the heat generated during machining in a relatively short time. Cryogenic machining can significantly reduce the cutting temperatures at the tool-workpiece interface, thereby improving the surface integrity of the manufactured components. This dissertation presents the results of experimental and numerical investigations of the effects of different cooling conditions on the machining performance and machining-induced surface integrity of Ti-6Al-7Nb and Ti-5553 alloys. Surface integrity and residual stresses induced by cryogenic machining are studied and compared with dry machining. Corrosion tests were also conducted to study the influence of machining parameters on the corrosion resistance of machined Ti-6Al-7Nb alloy. The results of the numerical and experimental studies show that compared with dry machining, cryogenic machining generates superior surface finish, along with higher surface layer hardening. The sub-surface residual stress profile is more compressive after cryogenic machining, and evidence of nanostructured grains is also observed in the influenced surface layer under both cooling conditions. Also, cryogenically-cooled machined sample showed better corrosion resistance compared with dry machined sample

Evaluation of subcooled MQL in cBN hard turning of powder-based Cr-Mo-V tool steel using simulations and experiments

Metal cutting fluids for improved cooling and lubrication are an environmental risk and a health risk for workers. Minimizing water consumption in industry is also a goal for a more sustainable production. Therefore, metal cutting emulsions that contain hazardous additives and consume considerable amounts of water are being replaced with more sustainable metal cutting fluids and delivery systems, like vegetable oils that are delivered in small aerosol droplets, i.e., via minimum quantity lubrication (MQL). Since the volume of the cutting fluid in MQL is small, the cooling capacity of MQL is not optimal. In order to improve the cooling capacity of the MQL, the spray can be subcooled using liquid nitrogen. This paper investigates subcooled MQL with machining simulations and experiments. The simulations provide complementary information to the experiments, which would be otherwise difficult to obtain, e.g., thermal behavior in the tool-chip contact and residual strains on the workpiece surface. The cBN hard turning simulations and experiments are done for powder-based Cr-Mo-V tool steel, Uddeholm Vanadis 8 using MQL subcooled to −10 \ub0C and regular MQL at room temperature. The cutting forces and tool wear are measured from the experiments that are used as the calibration factor for the simulations. After calibration, the simulations are used to evaluate the thermal effects of the subcooled MQL, and the surface residual strains on the workpiece. The simulations are in good agreement with the experiments in terms of chip morphology and cutting forces. The cutting experiments and simulations show that there is only a small difference between the subcooled MQL and regular MQL regarding the wear behavior, cutting forces, or process temperatures. The simulations predict substantial residual plastic strain on the workpiece surface after machining. The surface deformations are shown to have significant effect on the simulated cutting forces after the initial tool pass, an outcome that has major implications for inverse material modeling

Machinability assessment when turning AISI 316L austenitic stainless steel using uncoated and coated carbide inserts

Austenitic stainless steel AISI 316L is mostly used as an implant material and is customarily applied as impermanent devices in orthopedic surgery because of its low cost, adequate mechanical properties, and acceptable biocompatibility. AISI 316L is an extra-low carbon type 316 (austenitic chromium nickel stainless steel containing molybdenum) that minimizes harmful carbide precipitation at elevated temperature. Machining is part and parcel during the fabrication of implants and medical devices made from stainless steels and thus it is of interest to evaluate the machinability of AISI 316L. In this study, austenitic stainless steel AISI 316L was turned using two commercially available cutting tool inserts at various cutting speeds (90, 150, and 210 m/min) and feeds (0.10, 0.16, and 0.22 mm/rev) and at a constant depth of cut of 0.4 mm. The turning of AISI 316L was implemented in dry cutting. The cutting tools used were an uncoated tungsten carbide-cobalt insert (WC-Co) and a multi coated nano-textured TiCN, nano-textured Al2O3 thin layer, and a TiN outer layer insert. The cutting forces, total power consumption, surface roughness, and tool life were measured/obtained and analyzed. The total power consumption of the turning process was obtained from direct measurements as well as using a combination of theoretical formulas and experimental cutting force data. The machining experiments and their responses were designed and evaluated using the three-level full factorial design and the analysis of variance (ANOVA). It was found that the cutting speed and feed significantly affect the various machining responses observed. The cutting force and total power consumption increased with increasing cutting speed, but the surface roughness and tool life decreased. With increasing feed, surface roughness and tool life decreased but the cutting force and total power consumption increased. The empirical mathematical models of the machining responses as functions of cutting speed and feed developed were statistically valid. Confirmation runs helped to prove the validity of the models within the limits of the factors investigated

Progressing towards sustainable machining of steels : a detailed review

Machining operations are very common for the production of auto parts, i.e., connecting rods, crankshafts, etc. In machining, the use of cutting oil is very necessary, but it leads to higher machining costs and environmental problems. About 17% of the cost of any product is associated with cutting fluid, and about 80% of skin diseases are due to mist and fumes generated by cutting oils. Environmental legislation and operators’ safety demand the minimal use of cutting fluid and proper disposal of used cutting oil. The disposal cost is huge, about two times higher than the machining cost. To improve occupational health and safety and the reduction of product costs, companies are moving towards sustainable manufacturing. Therefore, this review article emphasizes the sustainable machining aspects of steel by employing techniques that require the minimal use of cutting oils, i.e., minimum quantity lubrication, and other efficient techniques like cryogenic cooling, dry cutting, solid lubricants, air/vapor/gas cooling, and cryogenic treatment. Cryogenic treatment on tools and the use of vegetable oils or biodegradable oils instead of mineral oils are used as primary techniques to enhance the overall part quality, which leads to longer tool life with no negative impacts on the environment. To further help the manufacturing community in progressing towards industry 4.0 and obtaining net-zero emissions, in this paper, we present a comprehensive review of the recent, state of the art sustainable techniques used for machining steel materials/components by which the industry can massively improve their product quality and production

ENHANCED SURFACE INTEGRITY WITH THERMALLY STABLE RESIDUAL STRESS FIELDS AND NANOSTRUCTURES IN CRYOGENIC PROCESSING OF TITANIUM ALLOY TI-6AL-4V

Burnishing is a chipless finishing process used to improve surface integrity by severe plastic deformation (SPD) of surface asperities. As surface integrity in large measure defines the functional performance and fatigue life of aerospace alloys, burnishing is thus a means of increasing the fatigue life of critical components, such as turbine and compressor blades in gas turbine engines. Therefore, the primary objective of this dissertation is to characterize the burnishing-induced surface integrity of Ti-6Al-4V alloy in terms of the implemented processing parameters. As the impact of cooling mechanisms on surface integrity from SPD processing is largely unexplored, a particular emphasis was placed upon evaluating the influence of cryogenic cooling with liquid nitrogen in comparison to more conventional methodologies. Analysis of numerical and experimental results reveals that burnishing facilitates grain refinement via continuous dynamic recrystallization. Application of LN2 during SPD processing of Ti-6Al-4V alloy suppresses the growth of new grains, leading to the formation of near-surface nanostructures which exhibit increased microhardness and compressive residual stress fields. This is particularly true in cryogenic multipass burnishing, where successive tool passes utilizing lower working pressures generate thermally stable work hardened surface layers, uniform nano-level surface finishes, and significantly deeper layers of compressive residual stresses