Abstract: Inconel718 is a superalloy, considered one of the least machinable materials. Tools must withstand a high level of temperatures and pressures in a very localized area, the abrasiveness of the hard carbides contained in the Inconel718 microstructure and the adhesion tendency during its machining. Mechanical properties along with the low thermal conductivity become an important issue for the tool wear. The finishing operations for Inconel718 are usually performed after solution heat treatment and age hardening of the material to give the superalloy a higher level of hardness. Carbide tools, cutting fluid (at normal or high pressures) and low cutting speed are the main recommendations for finishturning of Inconel718. However, dry machining is preferable to the use of cutting fluids, because of its lower environmental impact and cost. Previous research has concluded that the elimination of cutting fluid in these processes is feasible when using hard carbide tools. Recent development of new PCBN (Polycrystalline Cubic Boron Nitride) grades for cutting tools with higher tenacity has allowed the application of these tool grades in the finishing operations of Inconel718. This work studies the performance of commercial PCBNtools from four different tool manufacturers as well as an additional grade with equivalent performance during finishturning of Inconel718underdryconditions. Wear tests were carried out with different cutting conditions, determining the evolution of machining forces, surface roughness and tool wear. It is concluded that it is not industrially viable the high-speed finishing of Inconel718 in a dry environment.
The characteristics of the enco alloys cause high temperature (1000°C) and stresses ( 3450 MPa) in the cutting zone leading to accelerated flank wear, chattering and notching, depending on the tool material and cutting conditions used Ezugwu et al (1991).The material results in high temperature stress and a thick adhering layer at the tool-work interface during machining. The toughness results in difficulty in chip breaking during the process. These difficulties lead to high tool wear less material remove rate (MRR) and poor surface finish. The metallurgical damage to the workpiece due to the very high cutting forces which also gives rise to work hardening, surface tearing and distortion in finally machined components due to induced stresses. Rahman et al (1997) Choudhury et al (1998). The tendency to form a BUE during machining and the presence of hard abrasive carbides in their microstructure also deters machinability. The combination of highspeed cutting and dry cutting for difficult-to-cut aerospace materials is the growing challenge to deal with the economic, environmental and health aspects of machining. Added advantages of dry machining are non-pollution of atmosphere or of water, no residue of lubricant on machined components and no residue of lubricant on evacuated chips which reduces disposal costs and the associated energy consumption. D. Dudzinski et al (2004).
D Dudzinski (2004) focused mainly on the developments towards dry and highspeed machining of inconel718. He has used different types of cutting tools and has concluded that cemented carbide tool are largely used for machining nickel based alloys at very low cutting speed at 20 - 30 m/min the K20 grade appears to be the best for cutting inconel718 higher cutting speed certainly upto 100 m/min underdry condition may be achived wuth coated carbide tools. The use of coolent is undesirable for environment hence new concept has been introduced to minmised coolent lubrication the objective of this paper is to find the suitable tool an appropriate coating to define the better geometrical tool configuration.
In aerospace applications Nickel-based super alloys are widely used due to their magnificent corrosion resistance and mechanical properties maintained at high temperature. Especially Machining of Ni based alloys is still a challenge in dry machining. Super alloys characteristics like high temperature, tensile strength, shear strength, strain hardening, decrease in thermal conductivity, built up edge formation and the occurrence of abrasive particles in their microstructures etc. are induce high thermo-mechanical loads at the tool-chip interface resulting in important wear of the tool . Cemented carbide inserts were not suitable to machine Ni based alloys at highspeed since they cannot survive the conditions of acute high temperature and stress in the cutting zone. In general, the suggested range of cutting speeds up to 30 m/min for uncoated tools and up to 100 m/min when machining Ni-based alloys using cemented carbide inserts properly coated . Ceramic tools have been used gradually more In metal-cutting processes tool wear is a complex phenomenon occurring in various ways.
The paper deals with experimental investigation on machinability of Inconel718 in conventional and alternative high pressure cooling conditions. The experiments are designed according to Taguchi L18 orthogonal array based on three levels of cutting speed, feed rate and fluid pressure and two levels of depth of cut. The cutting forces and tool flank wear were measured, while turningInconel718 workpieces, using (Ti, Al)N+TiN coated CNMG0812 carbide cutting tools. In order to determine the importance of cutting parameters on tool flank wear and cutting forces, ANOVA (Analysis of variance) was employed. Moreover, with multi regression analysis, empirical equations that indicate relation between tool flank wear and cutting forces with machining parameters were defined. The experiment results have proven that the tool flank wear and cutting forces considerably decrease with the delivery of high pressure coolant to the cutting zone. Moreover, ANOVA results also indicate that high pressure cooling has a significant beneficial effect on cutting tool life.
S/N response graph on Figure-4 shows the effect of the machining factors on the roughness of milled surface. A steep slope for the cutting conditions (factor D) indicates this parameter is the most significant factors followed by the frequency (factor C). However, the factors of the cutting speed (factor A) and feed rate (factor B) found to be insignificant. It was supported by the Max- min table on Table-4 to rank each input parameter. By comparing these cutting conditions, D2 parameter is found the highest of S/N ratio showing the cutting with flooded coolant results better surface finish compare to dry and pulsating coolant condition. Secondary most significant factor of ultrasonic setting indicating that the frequency of 27 kHz (C3) assists in low surface roughness. In conclusion, the surface roughness can be improved by implementing flooded with high frequency vibration during the cutting process.
Hard machining of materials is emerging as new process to reduce the cycle time, tool wear, obtain good surface roughness, cost reduction and dimensional accuracy. Machining of hard materials is difficult by highspeed steel, ceramic tools, even more difficult on material like titanium alloy, Inconel718 and martensitic stainless steel. These are all difficult to cut materials. Few attempts have been made on the machinability of hard martensitic AISI 440 C and SCM 440 alloy steel with respect to chip thickness ratio, shear angle, flank wear using CBN and PCBNtools. These tools are considered for cutting due to increased demand on surface quality and less tool wear. Machinability is poor in turning stainless steel owing to low thermal conductivity, high ductility, high strength, high fracture toughness and rate of work hardening. Work hardening of stainless steel is caused after a previous severe cutting operation by worn tool . Sethilkumar et al.  turned hard martensitic stainless steel and found that it produced saw tooth chips in all operating parameters which increased the cutting forces. Turning of SCM 440 alloy steel
A high nickel alloy is well known as a difficult-to-cut material. Nickel alloys work hardens rapidly. The high pressures produced during machining cause a hardening effect that makes further machining more difficult, and may also cause warping in small parts. Severe tool injury usually occurs in machining nickel alloys. Rapid tool wear in machining has long been recognized as a challenging problem [Ouh (1983), Zlatin (1975)]. So far, researches conducted for the machining of Inconel718 are mainly focused on machining characteristics [Komanduri(1986)], and the appropriate tool material, geometry, and cutting conditions for machining. There are several studies on the machining of nickel base alloys by ceramics in recent years [Narutaki et al (1993) Vigneau et al (1987)]. Comparatively, very few have been done to identify tool wear mechanism during machining of Inconel718.
Due to the fast development in the domain of communication and an ongoing trend of digitization and digitalization, manufacturing enterprises are facing important challenges in today’s market environments: a continuing tendency towards reduction of product development times and shortened product lifecycles. In addition, there is an increasing demand of customization, being at the same time in a global competition with competitors all over the world. This trend, which is inducing the development from macro to micro markets, results in diminished lot sizes due to augmenting product varieties (high-volume to low-volume production) . To cope with this augmenting variety as well as to be able to identify possible optimization potentials in the existing production system, it is important to have a precise knowledge
These experiments were with two cutting conditions; dry and chilled air. The parameters range study based on the suggestion from tool manufacture (SUMITOMO General Cataloque, 2018) as shown in Table 3. The axial depth cut was set at 0.1 mm for the finishing process. It was similarly done by (Kurt, 2009) who investigated the cutting tool which recommends that value as to obtain minimum residual stresses on the workpiece. Based on full factorial approach as the design of the experiment, a total of 8 runs were performed throughout the experiment. For each runs, the fresh TiAlN PVD coated carbide cutting tool were used. The insert wears measured every subsequent cutting path by using toolmaker microscope. Experiment stops when the flank wear, VB 1 reaches
A regular insert was textured on the rake face by laser ablation method. Cylindrical dimple shapes were placed perpendicular to the surface and in a periodic array of seven rows. This textured insert is named Gen 0 insert and the design is illustrated in Fig. 2 . Gen 0 structures were created using a pulsed Nd-YAG laser, LASER diode LD50C, operated at 1064 nm. Optimized laser pulse parameters were used as follows: pulse duration of 120 ns; frequency of 2.5 kHz; en- graving time of 10 ms, laser spot size of 100 μm with output power of 15 W. Seven rows of dimple textures were generated parallel to the cutting edge. The distance between each row is 0.25 mm, which is a constant value. The pitch is of 0.25 mm for the first row close to the cutting edge, see Fig. 2 (b), the pitch value decreases for the rows closer to the centre of the insert, due to the geometry of the insert. The po- sition of the first row of dimples was placed on the facet and 0.1 mm away from the cutting edge as shown in the Fig. 2 (b). Every cylindrical dimple was designed for a diameter and depth of 0.1 mm, see Fig. 2 (d). Based on the preliminary optimization experiments, the dimple dia- meter, pitch and position from the cutting edge were chosen. The Gen 0 design has no negative effect on the structural integrity of the cutting tool. The real diameter of the dimple was measured as 0.078 mm in average. This is caused by the Gaussian mode of power density
Allaudin et al.  modelled the cutting forces and observed that cutting force increase with an increase in feed and axial depth of cut. Flank and crater wear are the two main wear mechanisms that limit cutting tool performance. Flank wear is caused when the relief face of the tool rubs against the machined surface and on other hand crater wear occurs on the rake face of the tool and affects the geometry at the chip tool interface, which in turn affects the cutting force . Pavel et al. performed a number of experiments to investigate effect of tool wear on surface produced and observed that as flank wear increases with cutting time, machined surface became rougher. Also according to the ISO 8688-2, the tool rejection criteria of averaged flank wear 0.3 mm is used for tool replacement during machining . Tool life in turning and drilling of nickel alloys is widely investigated. Hence, tool life in milling has limited attention. Life of uncoated tools for machining of Inconel is very short as compared to the coated tools, also it is realized that very little work is done on analytical modelling of tool wear progression of the end milling cutters. Thus, the main focus of this research is to analyze the effect of progression of flank wear using nitrided tungsten carbide flat end milling cutter on surface produced.
Abstract - AISI1040 are extensive applications in industries due to the demand of steel in upcoming days. The way to meet the consumer demand is to raise the rate of production and operation. The raises in rate of production causes creation of high heat zone at the tool and also spoil the quality of the product. But no compromise can be allowed with surface finish and dimensional accuracy of the product. In order to solve these problems during machining is to use coated cutting toolsunder optimum cutting conditions. So this research is concentrated on TiCN/TiN and TiAlN coated tools for turning AISI1040 underdry condition. Performance of the both the cutting tool are compared. The optimum parameter is obtained from Taguchi technique and significant parameter is obtained from Analysis of variance for coated cutting tools.
about shot peening nickel alloys [1, 14, 21]. Ul- trasound shot peening (USP) rebuilds the geom- etry structure of nickel alloys. Machining traces are “punched” on the surface, which depth and amount on the surface depends on the material, of which the balls are made, the processing time and the impact energy . The use of too much pres- sure during the machining of Inconel718 nickel alloy results in an increase in surface roughness, which is due to the insufficient ability to absorb the deformation by the machined surface [14, 21]. During the finishing treatment of nickel al- loys, the physical properties of the surface layer are changed. As a result of the conducted shot peening of the Inconel718 alloy, compressive stresses are deposited on the surface layer [19, 20], which translates into the increased fatigue strength [1, 3]. The stress depth and its value de- pends on the machining time, material of the balls and the distance at which the workpiece is located from the nozzle .
Fig 3 (a) shows the main effects plot for Surface roughness for EN-31-dry.The surface roughness improves as speed increases from 630 to 840; it decreases for speed range 840 to 1000; similar trend is seen for feed. Surface roughness remained constant for DOC 0.5 to 1.0 and then decreased slightly between ranges 1.0 to1.5. Fig 3 (b) shows interaction plots for Speed v/s Feed, Speed v/s DOC, and Feed v/s DOC for EN-31-dry. The observations disclose that the unit variation of surface roughness for medium and high speeds is very less for low and medium feed rate. There is drastic variation at low speed. Better surface roughness was obtained at highspeed and low feed, least Ra was obtained at low speed and low feed evidently. At low speed it is observed that Ra improves as DOC increases. At medium speed Ra has remained fairly same irrespective of DOC.Lowest Ra is obtained at low feed and low DOC. Fig 3 (c) shows the graphical comparison of Ra for EN-31-dry. The model predicts the value with good accuracy.The equation is given below.
Caution should be taken with the results presented in this paper, as there are many factors that will contribute to the surface roughness. It can be concluded that although an increased wear rate is present during dry condition; the direct and indirect costs of coolant alone will outweigh the increased frequency for purchasing of new cutting tips. During rough cutting it was noted that a high surface roughness was present with dryconditions, but was still at an acceptable level for non-interfacing surfaces, which would suggest that for pure material removal operations, dry cutting is the most cost effective despite the slight increase in tool ware. Comparing wet and dryfinish cutting, it will be highly depended on the intended application and the required amount of material needing to be removed, as a compromise needs to be made between the use of coolants and a slightly higher surface roughness, as well as time of manufacturing. With coolant, it will be possible to further increase cutting feed rate without over heating the tool, however, for single one off jobs, fluid is not justifiable and a slower feed rate should be employed with dryconditions. As a result of the slight increase in tool ware, it is recommended that for prolonged cutting jobs, dryconditions can be used for material removal with coolant applied for the finish turn as this will drastically reduce the volume of coolant used during the operation, while still providing an acceptable level of surface roughness. It should also be Fig.6. 3D surface analysis on cutting tip for dryconditions
eroengine manufacturers have to demonstrate that critical components such as turbine disks meet the certification requirements in term of fatigue crack propagation life, using damage tolerance approaches. Crack propagation laws are usually identified from sinusoidal wave shape fatigue tests. Trapezoidal wave shape signal tests, with a hold time at maximum load, are also studied as they are more representative of the in service loading conditions (i.e. the take off – cruise – landing cycle). This study aims at investigating the deleterious effect of hold time on the crack propagation behaviour of DA Inconel718 [1-3], a polycrystalline nickel based superalloy widely used for aeroengines turbine disks manufacturing. Modelling the hold time effect is challenging as models have to take into account the coupled effects of fatigue, creep and environment (see e.g. [4-6]). Established models are often conservative. Introducing the crack growth threshold under hold time conditions in models is a way to reduce the degree of conservatism. This paper focuses on the characterization of the crack growth threshold under hold time conditions and crack growth mechanisms involved in the low ΔK regime.
exceeded the reference case and they were not suitable for cutting Inconel718 at this cutting speed (Fig. 2). The EDS (electron-dispersion spectroscopy) analyses were obtained using a scanning electron m icroscope in order to determ ine the chem ical elements present in the cutting tools (Fig.3, Fig. 4, and Table 5). From the EDS results we can see that the composition contains mainly Si, Al and C for the KYON 2100 SNGN tool, and that this cutting tool is subj ected to general BUE and crater wear. The KY ON 4300 SNGN cutting tool, having Al, O and Si in its structure, showed better performance at low cutting speeds, as shown in Fig. 2. The other inserts, KYON 2000 R N G N 12 07 00 and KYON4300 R N G N 120700, did not show a satisfactory performance. The KYON 2000 RNGN ceramic tool showed excessive wear compared to the other inserts (Fig. 2 and Fig.5). From the EDS analysis o f this cutting tool, one can see that the levels o f Si and Al are very high (Fig. 3), which contributes to the notch formation.
The machining tests were performed by single point continuous turning on a Kirloskar Turn master-35 me- dium duty lathe, with a variable speed of up to 1500 rpm and a power rating of 3 HP. The tests were conducted without the application of cutting fluid (dryturning). The cutting tools used were TiC and TiCN coated carbide inserts produced by Tagutec and had SNMG 120408 MT TT5100 Tagutec designation. These inserts were clamped mechanically on a pin and hole type rigid tool holder with a general specification of PSBNR 2525M12. Cut- ting speeds used ranges from 80 to 160 m/min. The cut- ting speed was increased in steps of 20 m/min. Feed rates used ranges from 0.04 to 0.12 mm/rev. The feed rate was increased in steps of 0.04 mm/rev. The depth of cut was kept as constant i.e., 0.5 mm. Surface roughness meas- urement was carried out on the machined surfaces using a TIME surface roughness tester (TR100). The Piezo- electric stylus was used for taking the surface roughness measurements. Three measurements were made on the machined surface at three different locations and the av- erage value was taken.
many parts can be assembling virtual environment to create a computer model of the finished product. In addition, traditional engineering drawings can be easily extracted from the solid models of both the parts and the final assembly. This approach opens the door to innovative design concepts, speeds product development, and minimizes design errors. The result is the ability to bring high-quality products to market very quickly. Solid modelling represents objects in a computer as volumes, rather than just as collections of edges and surfaces.