Scholarly article on topic 'Tool Wear and Chip Characteristics during Dry Turning of Inconel 825'

Tool Wear and Chip Characteristics during Dry Turning of Inconel 825 Academic research paper on "Materials engineering"

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{"Inconel 825" / "Flank wear" / "uncoated carbide inserts" / "PVD multilayer" / "chip thickness ratio" / "chip morphology."}

Abstract of research paper on Materials engineering, author of scientific article — A. Thakur, A. Mohanty, S. Gangopadhyay, K.P. Maity

Abstract Nickel-based super alloys are widely utilized in engineering applications especially in the aerospace sectors. One such alloy belonging to Nickel based family which has been extensively used by the researchers for the study of machinability is Inconel 718. Recently Inconel 825 with much superior resistance to corrosion than Inconel 718 is of little attention to researchers. The high corrosion resistance property of Inconel 825 finds its application in chemical processing, nuclear fuel reprocessing, acid production and pickling equipment apart from its general aerospace industries. However, not much research work has been reported on Inconel 825. The present work investigates the effect of cutting speed on tool wear and chip characteristics during dry turning of Inconel 825 with uncoated and physical vapour deposition (PVD) multilayer coated (TiN/TiAlN) cemented carbide inserts. The machining with PVD multilayer coated insert resulted in better tool wear performance.

Academic research paper on topic "Tool Wear and Chip Characteristics during Dry Turning of Inconel 825"

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Procedia Materials Science 5 (2014) 2169 - 2177

International Conference on Advances in Manufacturing and Materials Engineering,

AMME 2014

Tool Wear and Chip Characteristics during Dry Turning of Inconel

A.Thakura*, A. Mohantya, S.Gangopadhyaya, K.P.Maitya

"Department of Mechanical Engineering, National Institute of Technology, Rourkela- 769008, Odisha, India.

Abstract

Nickel-based super alloys are widely utilized in engineering applications especially in the aerospace sectors. One such alloy belonging to Nickel based family which has been extensively used by the researchers for the study of machinability is Inconel 718. Recently Inconel 825 with much superior resistance to corrosion than Inconel 718 is of little attention to researchers. The high corrosion resistance property of Inconel 825 finds its application in chemical processing, nuclear fuel reprocessing, acid production and pickling equipment apart from its general aerospace industries. However, not much research work has been reported on Inconel 825. The present work investigates the effect of cutting speed on tool wear and chip characteristics during dry turning of Inconel 825 with uncoated and physical vapour deposition (PVD) multilayer coated (TiN/TiAIN) cemented carbide inserts. The machining with PVD multilayer coated insert resulted in better tool wear performance.

© 2014ElsevierLtd.This isanopenaccessarticleunder the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of Organizing Committee of AMME 2014

Keywords: Inconel 825; Flank wear; uncoated carbide inserts; PVD multilayer; chip thickness ratio; chip morphology.

* Corresponding author: E-mail: ar_aruna_tk@yahoo.co.in Tel.:+ 91- 8093267596

1. Introduction

Nickel based super alloys are termed as difficult-to-cut material as it possess superior mechanical properties such as high yield strength, high fatigue strength and ultimate tensile strength at elevated temperature which also makes them suitable to be used particularly in aerospace, marine, defence and nuclear sectors (Arunachalam & Mannan , 2000; Choudhury and El-Baradie, 1998; Ezugwu, 2005). Nickel-based super alloys find immense use in

2211-8128 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Selection and peer-review under responsibility of Organizing Committee of AMME 2014 doi:10.1016/j.mspro.2014.07.422

manufacturing of aircraft turbines, steam turbines power plant, reciprocating engines, medical applications, metal processing, space vehicles, heat treating equipment, chemical and petrochemical industries, nuclear power systems, pollution control equipment and coal gasification and liquefaction systems (Choudhury and El-Baradie,1998). Therefore it necessitates studying machinability aspects of such alloys in order to increase both productivity and quality in the above sectors. Inability to sustain at high temperature makes aluminium and steel unsuitable for aero engines and other high temperature applications (Arunachalam & Mannan, 2000; Ezugwu et al., 1998; Ezugwu et al., 2003; Ezugwu, 2005).

Tool wear and chip characteristics are two of important indices of machinability. During the machining operation, chip formation plays a very vital role since it gives an indirect measurement of specific energy requirement. Considerable improvement in surface roughness as well as tool life was observed with proper handling of chip (Bhatt, 2010; Liao and Shiue, 1996). Therefore it is important to analyse the chip characteristics and chip morphology. Various investigations were carried out to study chip characteristics. Transition of continuous chip at low cutting speed to saw-tooth type chip was observed at high cutting condition (Thakur et al., 2009a). Experiments were also carried out to investigate the effect of high pressure coolant on chip fragmentation during the machining of Inconel 901 (Machado et al., 2009). Tool wear is another aspect of evaluating the performance of machining. In order to get high performance of any tool during machining, judicious selection of cutting tool, cutting parameters, type of coating, machining environment (dry or wet) should be made. The preferred cutting tool for the machining of Nickel-based superalloy is cemented carbide tool sustaining high temperature generated at chip-tool interface (Ezugwu, 1998). Recently various ceramic tools were used by different researchers to improve the tool performance at high cutting speed (Richards and Aspinwall, 1989). Different tool wear mechanism was proposed by several researchers during turning of Inconel 718, most dominating tool wear being notching, flank wear and depth of cut (DOC) line (Bhatt, 2010; Choudhury and El-Baradie, 1998; Ezugwu and Bonney, 2005). The use of different types of coated tool (CVD or PVD) with different layers of coatings (Single layer or multi-layer) also enhances the tool performance by preventing the tool wear to occur at early stage of machining. Several investigations were conducted to study the effect of different coated tools on tool wear at different cutting conditions during turning on Inconel 718 (Jindal et al., 1999; Thakur et al., 2012). The use of different types of cooling method reduces friction generated at the chip-tool interface which helps in improving the tool wear during machining as proposed by several researchers (Kamata and Obikawa, 2007; Obikawa et al., 2012). Cutting parameters do play a vital role in influencing the tool wear or tool performance during machining. Cutting speed and feed rate were found to be most dominating factor during turning of Inconel 718 (Ham, 1975). Uncoated tool performed better at low cutting speed and intermediate feed rate while multilayer coated tool performed better at high cutting speed and low feed rate during the machining of Inconel 718 (Bhatt, 2010).

The previous researchers mostly focused on machining study of Inconel 718 with respect to different cutting tools and at various cutting conditions. Inconel 825 is another member of the group of Nickel-based superalloys with superior chemical, corrosion and oxidation resistance than that of Inconel 718. Hence Inconel 825 finds application mostly in nuclear fuel processing, pollution control equipment, oil & gas well piping, chemical processing, acid production & pickling apart from its general use in aerospace, marine, defense and nuclear sector. In this paper an experimental investigations were performed on Inconel 825.The dry turning operation of Inconel 825 was carried out with variable cutting speeds (Vc) of 51 and 84 m/min with constant feed (f) of 0.15 mm/rev and depth of cut (t) of 1 mm. A comparison of machining performance of Inconel 825 with respect to tool wear and chip characteristics were made during machining with uncoated and coated(TiN/TiAlN) cemented carbide tools.

Nomenclature

Vc Cutting speed, m/min

f Feed rate, mm/rev

t Depth of cut, mm

r Chip thickness ratio

to Uncut chip thickness

tc Cut chip thickness

2. Experimental Details

2.1. Material used

A cylindrical rod of Inconel 825 with 75 mm diameter and 195 mm length was used as a workpiece for the purpose of experiment. Chemical composition of Inconel 825 is given in Table 1.

Table 1 : Chemical composition of Inconel 825

Element Weight %

Ni 38-46

Fe 22 min

Cr 19.5-23.5

Mo 2.5-3.5

Cu 1.5 3

Ti 1.2

2.2. Experimental setup

Heavy duty lathe (Make: Hindustan Machine Tools (HMT) Ltd., Bangalore, India; Model: NH26) was used for dry turning of Inconel 825 using uncoated and PVD multilayer coated cemented carbide inserts. Fig.l. shows the photograph of experimental setup for turning operation of Inconel 825.

Fig.l. Photograph of Experimental Setup for Turning of Inconel 825

2.3. Cutting parameters, cutting tool and tool holder

The experiment was conducted in dry environment with two different cutting speeds (51 and 84 m/min) at a constant feed rate of 0.15mm/rev and depth of cut of 1 mm. Uncoated and commercially available PVD multilayer (TiN/TiAIN) coated cemented carbide inserts with tool designation of SNMG 12 04 08 (Make: SECO) were used with the tool holder of ISO PSBNR 2020 K12 (Make: WIDIA, India). Machining operations were carried out progressively with different durations using both uncoated and coated tools.

2.4. Measurement of tool wear and chip morphology

A scanning electron microscope (SEM, Make: JEOL JSM-6490) and a stereo zoom microscope (Make: Radical Instruments) were used to analyse the tool wear and chip morphology.

2.5. Chip thickness ratio (r)

Another aspect of chip that was analysed is chip thickness ratio. Chip thickness ratio is defined as the ratio of uncut chip thickness (t„) to cut chip thickness (tc) as shown in equation 1 .Chip thickness was measured with the help of a digital vernier calliper (Make: Mitutoyo, Japan). Measurement of chip thickness ratio was taken at five different locations of each specimen for better statistical accuracy and the mean values were plotted.

where ta =f sin<l>.

where ® is the approach angle of the tools and its value is 75°. 3. Results and Discussion

3.1. Chip morphology

Fig.2 shows the optical microscopic images of chip with progression of the machining duration at different cutting speeds of 51 and 84 m/min using uncoated and PVD coated carbide inserts. It was noted that as machining duration increased from 51 to 84 m/min, continuous chips with large curl radii were formed while machining with uncoated carbide inserts. Similar observation was noted when cutting speed was increased (Tekiner & Yesilyurt, 2004).This can be attributed to high tool wear rate of uncoated carbide inserts with progression of machining duration as well increase in cutting speed. Whereas in case of PVD multilayer coated tools, the chips formed at initial duration of machining was of segmented form but as machining duration progresses the chip become long and continuous type. During machining duration of 180 s the chips obtained were of snarled type for both the cutting speeds.

Machining duration, s

Uncoated

Coated

Vc=51,f= 0.15 mm/rev, t=l mm and Environment Dry

Segmented chip

Long continuous coiled chips

Vc=84 m/min, f= 0.15 mm/rev, t=l mm and Environment Dry

Fig.2. Optical microscopic images of chips with progression of machining duration for different cutting speed of 51 and 84 m/min for

uncoated and coated insert

3.2. Chip thickness ratio

The cutting parameters have significant influence on the chip thickness ratio. Fig.3 depicts the effect of machining duration at two different cutting speeds on the chip thickness ratio during dry machining of Inconel 825 with uncoated and coated insert. As the machining duration progressed, the chip thickness ratio decreased for both cutting speeds (51 and 84 m/min). It can be due to the fact that with the progression of machining duration, the tool wear increases thereby generating high chip thickness. It was also observed that chip thickness ratio increased with increase in cutting speed (Thakur et al., 2009b). This occurred due to decrease in friction at tool-chip interfaces with increase in cutting speed which in turn reduces shear deformation or chip thickness. The multilayer TiN/TiAIN coated tool lowers the friction at the chip tool interface resulting in less deformation of chip than that of uncoated tool, hence resulting in high chip thickness ratio of coated tools.

0.90-, £ 0.84-| 0.78-

i 0.72-

JS ■

.a 0.66,

.& 0.60-o ■ 0.540.48-

Vc= 51 m/min, f= 0.15 mm/rev, DOC = 1 mm

- Uncoated

- Coated

0 40 80 120 160

Machining duration, s

S 0.84-1 .o

J 0.72-

0.54-1

Vc= 84 m/min, f= 0.15 mm/rev, t= 1 mm

- Uncoated

- Coated

40 80 120 160

Machining duration, s

Fig.3. Graph plotted between machining duration and chip thickness ratio at cutting speed of (a) 51 m/min and (b) 84 m/min using uncoated and

multilayer coated inserts

3.3. Study of tool wear

Tool wear during dry machining of Inconel 825 with both uncoated and coated carbide inserts were characterised by crater and flank wear which were investigated using optical microscopy. Fig.4 shows the optical microscopic images of 3D view of both rake surface as well as flank surface of the uncoated and coated carbide inserts with the progression of the machining duration for different cutting speeds. It is evident that with increase in cutting speed as well as with progression of machining duration, the tool wear increases (Thakur et al., 2009b) for both uncoated and PVD multilayer coated inserts. However the superiority of PVD multilayer coated tool can be explained due to high wear resistance of coating as compared to its counterpart uncoated carbide inserts.

Machining duration, s

Uncoated tool

Coated tool

51 m/min, f= 0.15 mm/rev, t=l mm and _Environment Dry_

Fig. 4. Optical microscopic 3D images of rake and flank surface (with magnification 40 X) of uncoated and coated inserts during the machining of Inconel 825 with variable machining duration and cutting speed of (a) 51 and (b) 84 m/min.

The growth of average flank wear with machining duration for different cutting speeds is represented in Fig.5. It is evident that the flank wear increases as with machining duration using uncoated and coated tools at different cutting speeds. One can also conclude by comparing Fig. 5 (a) and (b) that the flank wear at cutting speed of 84 m/min is higher than that of at 51 m/min for both uncoated and multilayer PVD coated carbide inserts. Explanation can be governed with high heat generation with the increase in cutting speed resulting in enhanced tool wear rate. The coated tool performed well as compared to uncoated tool at both cutting speeds. Fig. 6 shows SEM images of rake surface of tool wear for uncoated and coated inserts at cutting speed of 84 m/min after 180 s of machining duration. Deep crater wear is clearly visible on the rake surface of the uncoated tool.

(b) Vc= 84 m/min t=lmm

30 60 90 120 150 180 0 30 60 90 120 150 180

Machining duration, s Machining duration, s

Fig. 5. Variations of Hank wear with machining duration and cutting speed at (a) 51 m/min (b) 84 m/min for uncoated and coated inserts.

Cutting velocity of 84 m/min for 180 s of machining, feed rate 0.15 mm/rev _and depth of cut of 1 mm_

Uncoated

Adhesion wear

X5g'500Mm 12 40 SEI

Coated

Fig.6. SEM images of rake surface of tool wear for uncoated and coated inserts at cutting speed of 84 m/min after 180 sof machining duration.

4. Conclusions

The present research work investigated the effect of cutting speed on chip characteristics and tool wear during dry turning oflnconel 825 using uncoated and PVD multilayer coated inserts. The following conclusions may be arrived from the experiment:

• The chip curl radius increased with progression of machining duration and increase in cutting speed when machined with uncoated inserts.

• The chips obtained during dry turning of Inconel 825 with multilayer coated tool resulted in mostly long and continuous from of chip except at machining durations of 30 and 180 s.

• The chip thickness ratio decreased with progression of machining duration. The deformation of chip was more at low speed resulting in low chip thickness ratio than that at high cutting speed.

• The average flank wear increased with both cutting speed as well as with machining duration. However use of PVD multilayer coated improved the resistance to flank wear.

• It is therefore recommended to use coated carbide inserts for machining Inconel 825 at high velocity for better tool performance as well as productivity.

References

Arunachalam R., Mannan M.A., 2000. Machinability of nickel-based high temperature alloys. Min Sci Technol. 4(1), 127-168.

Bhatt, A., Attia, H., Vargas, R.,Thomson, V., 2010. Wear mechanisms of WC coated and uncoated tools in finish turning of Inconel 718. Tribology International 43(5), 1113-1121.

Choudhury, I.A., El-Baradie, M.A., 1998. Machinability of nickel-base super alloys: a general review. Journal of Materials Processing Technology 77(1), 278-284.

Ezugwu, E.O, 2005. Key improvements in the machining of difficult-to-cut aerospace superalloys. International Journal of Machine Tools and

Manufacture. 45, 1353-367.

Ezugwu, E.O., Bonney, J., 2005. Finish Machining of Nickel-Base Inconel 718 Alloy with Coated Carbide Tool under Conventional and High-Pressure Coolant Supplies, Tribology Transactions 48:1, 76-81.

Ezugwu, E.O., Bonney, J., Yamane, Y., 2003. An Overview of the Machinability of Aeroengine Alloys. Journal of Materials Processing

Technology. 134, 233-253.

Ezugwu, E.O., Wang, Z.M., Machado, A.R., 1998. The Machinability of Nickel-Based Alloys: a review. Journal of Materials Processing

Technology. 86, 1-16.

Ham, I., 1975. Computerised Machinability Study for Inconel-718, Influence of Metallurgy on Machinability. American Society for Metals, 324346.

Jindal, P. C., Santhanam, A. T., Schleinkofer, U., & Shuster, A. F., 1999. Performance of PVD TiN, TiCN, and TiAIN Coated Cemented Carbide Tools in Turning. International Journal of Refractory Metals and Hard Materials 17(1), 163-170.

Kamata, Y., Obikawa, T., 2007. High speed MQL finish-turning of Inconel 718 with different coated tools. Journal of Materials Processing Technology 192, 281-286.

Liao, Y.S., Shiue, R.H., 1996. Carbide tool wear mechanism in turning of Inconel 718 superalloy, Wear 193, 16-24.

Machado, A. R., Wallbank, J., Pashby, I. R., Ezugwu, E. O., 1998. Tool performance and chip control when machining Ti6A14V and Inconel 901 using high pressure coolant supply. Machining Science and Technology 2(1), 1-12.

Obikawa, T., Yamaguchi, M., Funai, K., Kamata, Y., Yamada, S., 2012. Air Jet Assisted Machining of Nickel-Base Superalloy. International Journal of Machine Tools and Manufacture 61, 20-26.

Richards, N., Aspinwall, D., 1989. Use of Ceramic Tools for Machining Nickel Based Alloys. International Journal of Machine Tools and

Manufacture. 29, 575-88.

Tekiner, Z., Ye§ilyurt, S., 2004. Investigation of the Cutting Parameters Depending On Process Sound during Turning of AISI 304 Austenitic Stainless Steel. Materials & Design 25(6), 507-513.

Thakur, D. G., Ramamoorthy, B., Vijayaraghavan, L., 2009a. Study on the Machinability Characteristics of Superalloy Inconel 718 during high speed turning. Materials & Design 30(5), 1718-1725.

Thakur, D. G., Ramamoorthy, B., Vijayaraghavan, L., 2009b. Machinability investigation of Inconel 718 in high-speed turning. The International Journal of Advanced Manufacturing Technology 45(5-6), 421-429.

Thakur, D. G., Ramamoorthy, B., Vijayaraghavan, L., 2012. Some Investigations on High Speed Dry Machining of Aerospace Material Inconel 718 UsingMulticoated Carbide Inserts, Materials and Manufacturing Processes 27:10, 1066-1072.