5th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT

Guwahati, Assam, India

108-1

Effect of Direct and Indirect Cryogen Application Methods on the Turning

Forces, Tool Wear and Surface Finish of a Nickel Based Alloy (Nimonic 90)

Chetan1*, Bikash Chandra Behera2, Sudarsan Ghosh3, P Venkateswara Rao4

1*Department of Mechanical Engineering, IIT Delhi, 110016, chetan.harry@gmail.com: 2 Department of Mechanical Engineering, IIT Delhi, 110016, bikash.nitr@gmail.com:

3Department of Mechanical Engineering, IIT Delhi, 110016, sudarsan.ghosh@gmail.com: 4Department of Mechanical Engineering, IIT Delhi, 110016, pvrao@mech.iitd.ernet.in:

Abstract

Due to the stricter environment legislation and also due to an increase in the occupational diseases amongst the

workers, it is necessary for the manufacturing sector to shift towards sustainable production techniques. Many

researchers have reported that the application of Cryogen in metal cutting could improve the machinability of some

materials without any ill effects on environment and health of workers. In machining, Cryogen can be used in two

ways: (a) direct method and (b) indirect method. In direct cryogen application method, cryogenic gas from a suitably

designed nozzle is directly applied to the tool-chip interface. While in indirect cryogen application cryogenic

treatment is done on the cutting tool which may be subjected to a temperature below 0 ͦC for a prolonged duration of

time. This paper presents the comparison between the direct and indirect cryogen application methods during

machining of Nimonic 90, a widely used nickel based super alloy. The measurement of Tool wear, surface

roughness and cutting forces has been carried out for both these methods to determine the more effective method

which can be used successfully during machining of the alloy. Keywords: Cryogenic cooling, Cryogenic treatment, Machinability, Nimonic, Sustainability

1 Introduction Machining is one of the most widely used

manufacturing operation all over the world. It has been

estimated that machining contributes towards 5% GDP

in developed world (Jayal et al., 2010). On the other

hand, it has also been noticed that machining operation

has detrimental effects on surrounding environment and

workers health (Marksberry, 2007). In order to make

machining operations more ecologically viable and

environmental friendly, it is necessary to introduce

sustainability in it. Sustainability in metal cutting

process can serve many benefits such as: 1) reduction in

overall cost, 2) reduction in power consumption, 3)

reduction in wastage, and 4) enhanced operational

safety. Several sustainable techniques like dry cutting,

cryogenic cooling (direct or indirect application),

minimum quantity lubrication (MQL) and compressed

air cooling have been evolved in recent years to make

machining process more cleaner and greener (Sharma et

al., 2009). Many difficult to machine materials like

Inconel 718 and Ti6Al4V based alloys have been

machined successfully using sustainable techniques

(Ezugwu et al., 2003). Nimonic is another important

nickel based alloy which is being widely used in

automobile, aerospace, marine and locomotive industry.

Despite of its poor machinability, very few literatures

are available about the machining characteristics of

Nimonic alloys.

2 Literature review

2.1 Sustainable machining techniques In machining operation it’s mandatory to use

cutting fluids or metal working fluids (MWFs) for

enhancing life of cutting tool and surface integrity of

work piece. It is an estimate that 16% of the total

manufacturing cost is associated with these MWFs

(Abele and Frohlich, 2008). The use of metal working

fluids is a biggest problem for manufacturing sector

because these are considered to be potential sources of

air and water pollution. These cutting fluids are also

cause of many respiration and skin related problems

amongst the workers. In order to eradicate these

problems, sustainable techniques like dry cutting,

cryogenic processing and cryogenic cooling are found

to be promising options (Lawal et al., 2013).

2.2 Dry cutting

In this process machining is performed in the

absence of pollution causing cutting fluids. Dixit et al.

(2012) suggested many advantages of dry cutting as

listed below

Effect of Direct and Indirect Cryogen Application Methods on the Turning Forces, Tool Wear and Surface Finish of a Nickel Based Alloy

(Nimonic 90)

108-2

• The problems like water and soil

contamination are absent in dry machining.

• No extra chemical treatment is required for

cleaning dry waste like swarfs and chips. The

solid waste can directly used for recycling

purpose.

• It also cut down the cost associated with

coolant thereby makes machining process more

economic.

• Dry machining also helps in improving tool

life in certain intermittent machining

operations like milling process.

Spur and Lachmund (1995) used CBN and ceramic

tools for machining of cast iron. They have concluded

that CBN tools are best suited for machining of cast iron

due their high thermal conductivity. Devillez et al.

(2007) tried machining of Inconel 718 with coated and

uncoated tools under dry mode. The magnitudes of

cutting and feed force were found to be more in

uncoated tools in comparison to coated tools. They

concluded that machinability of this alloy can further be

improved by doing nano structured coating on cutting

inserts. The methods such as: Surface texturing on

cutting tool, machining with solid lubricants and

minimum quantity lubrication can also be employed to

further enhance the sustainability of dry turning process.

2.3 Cryogenic processing

Cryogenic processing is the treatment of cutting tools

below 0 °C to enhance its mechanical properties. This is

an indirect cryogenic method in which various gases

such as CO2, nitrogen and helium are used in liquefied

form. Soaking temperature, cooling rate and tempering

rate are the main parameters considered during

cryogenic treatment. These terms have their usual

meaning as given below

• Soaking temperature: Temperature at which

specimen has to be placed for prolonged period.

• Cooling rate: Rate of change of temperature from

room temperature to soaking temperature.

• Tempering rate: rate of change of temperature from

soaking temperature to cooling temperature.

Many researcher have carried out this subzero treatment

on various tool steels by varying these important

parameters. Mohan Lal et al. (2001) have cryogenically

treated T1, M2 and D3 type tool steels. They have

achieved 110% increase in the tool life of T1 tool

followed by M2 and D3 tool steels. Meng et al. (1994)

have shown an increase of 600 % in the wear resistance

of tool steel by cryogenic processing. Recently, Gill et

al. (2011) carried out shallow (-110 °C) and deep (-196

°C) treatment of coated carbide tool. They were

successful in achieving 24% and 20% increase in the

tool life of shallow and deep treated tools respectively

during machining of C-65 steel.

2.4 Cryogenic cooling

This is also known as a direct method of cryogenic

application in which the jet of liquid nitrogen is applied

directly to the cutting zone. Many researchers have

achieved increase in tool life with the help of cryogenic

cooling. Cooling with cryogen not only removes heat

from cutting zone but also reduces the coefficient of

friction by making lubricating cushion between chip-

tool interface. Recently, Kaynak (2014) performed the

machining of Inconel 718 under dry, MQL and

cryogenic conditions. The temperature reduction of 50%

and 25% is achieved with cryogenic cooling as compare

to both dry and MQL conditions respectively. Similarly,

significant reduction in the amount of flank wear and

radial forces is obtained in cryogenic condition in

comparison to other conditions. Likewise,

Dhananchezian and Kumar (2011) have performed

machining of Ti6Al4V under cryogenic and wet

conditions. They have achieved a reduction of 35% in

surface roughness with cryogenic machining over wet

machining. The cryogenic cooling also helped in

reducing cutting forces, cutting temperature and tool

wear over wet machining.

2.5 Machining of Nimonic alloy

Nimonic alloys are widely used in making turbine

blades, hot working tools, high temperature springs,

exhaust valves, shafts, turbine rings and many other

high temperature resisting components. Ezugwu et al.

(2004) carried out machining of Nimonic C-263 alloy

with coated carbide tools using coolant of various

concentrations (3%, 6% and 9%). 3% coolant

concentration worked best at lower cutting speeds of 68

and 85 m/min for improving tool life. At higher cutting

speed of 136 m/min, 6% coolant concentration gave

best results followed by 9% and 3% coolant

concentrations. Recently during dry cutting of Nimonic

C-263 alloy, it has been observed that both feed rate and

depth of cut significantly influence the surface finish,

tool wear and cutting forces in comparison to cutting

speed (Ezilarasan et al., 2013).

Though Nimonic is an important alloy but very few

literatures are available regarding its machining. So, this

work is an attempt to gather more information regarding

machining characteristics of this alloy using sustainable

techniques.

5th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12

Guwahati, Assam, India

3 Experimental details

3.1 Workpiece Material

Nimonic 90 (UNS N07090) is nickel

cobalt based high temperature resistance super alloy.

This alloy is quite popular in aerospace industry because

of its high strength to weight ratio and high creep

resistance up to 920 °C. In the present study Nim

bar of 60 mm diameter and 300 mm length

used. The average micro hardness of this alloy was

found to be 445 HV, measured according

384-89 standard. Composition of this alloy has been

confirmed with the help of EDAX analysis

result of which is given in table 1.

Table 1: Chemical composition of Nimonic 90

Element Ni Cr Co

% 57.58 19.32 17.62

3.2 Cutting tool

Uncoated carbide inserts with sp

CNMG12408-THM-F have been used for carrying out

turning experiments. EDAX analysis of cutting tool was

also performed to know about its main constituent.

tool inserts consist of mainly tungsten, carbon and

cobalt (binder) listed in table 2.

Table 2: Composition of cutting inse

Element W C

% 84.61 8.39

3.3 Cryogenic treatment of cutting tool

(Indirect cryogenic application)

Cryogenic treatment enhances the wear

and hot hardness of cutting tool. To achieve this,

cryogenic treatment of carbide tools has been carried

out under controlled environment as shown in F

The cutting tools were kept at -

temperature for duration of eight hours. These inserts

were cooled from room temperature to soakin

temperature at a cooling rate of 2 °C/min. In order to

avoid thermal cracking the inserts were brought back to

room temperature at a heating rate of 1 °

in Figure 2.

All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12

Nimonic 90 (UNS N07090) is nickel-chromium-

cobalt based high temperature resistance super alloy.

This alloy is quite popular in aerospace industry because

of its high strength to weight ratio and high creep

C. In the present study Nimonic 90

and 300 mm length has been

average micro hardness of this alloy was

found to be 445 HV, measured according to ASTM-

89 standard. Composition of this alloy has been

the help of EDAX analysis and the

Nimonic 90 alloy

Ti Al

2.21 1.32

inserts with specifications

used for carrying out

EDAX analysis of cutting tool was

performed to know about its main constituent. The

tool inserts consist of mainly tungsten, carbon and

omposition of cutting insert

C Co

8.39 7.00

Cryogenic treatment of cutting tool

(Indirect cryogenic application)

Cryogenic treatment enhances the wear resistance

of cutting tool. To achieve this, deep

cryogenic treatment of carbide tools has been carried

as shown in Figure 1.

-196 °C soaking

temperature for duration of eight hours. These inserts

were cooled from room temperature to soaking

C/min. In order to

avoid thermal cracking the inserts were brought back to

erature at a heating rate of 1 °C/min as shown

Figure 1: Cryogenic treatment set

Figure 2: Cryogenic treatment

Many authors claimed that cryo-treatment of cutting

inserts leads to the precipitation of hard eta phase

particles. To confirm this claim, specimen of treated and

untreated carbide inserts has been prepared for

microstructure identification. ASTM B 6

procedures for the cemented carbides has been followed

to check any modification in the microstructure due to

sub zero treatment. Figure 3 revealed

between the microstructure of untreated and treated

inserts. Dense distribution of black

has been found in treated insert as compared to

untreated insert.

All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT

108-3

Cryogenic treatment set-up

Figure 2: Cryogenic treatment cycle

treatment of cutting

inserts leads to the precipitation of hard eta phase

specimen of treated and

untreated carbide inserts has been prepared for

microstructure identification. ASTM B 657- 05 standard

procedures for the cemented carbides has been followed

to check any modification in the microstructure due to

revealed the difference

between the microstructure of untreated and treated

black eta phase particles

has been found in treated insert as compared to

Effect of Direct and Indirect Cryogen Application Methods on the Turning Forces, Tool Wear and Surface Finish of a Nickel Based Alloy

(Nimonic 90)

108-4

Figure 3: microstructure of treated and untreated

insert. (a) Dense eta phase distribution in treated

inserts (b) Sparse eta phase distribution in untreated

insert.

3.4 Cryogenic cooling (Direct cryogenic

application)

In direct cryogen application method, cryogen has

been directly applied to the cutting zone as shown in

Figure 4. Unlike indirect cryogenic approach, untreated

tools have been used during direct cryogenic cooling

method.

Figure 4: schematic of direct cryogenic cooling

3.5 Experimental plan

All experiments have been carried out on Leadwell

T-6 turning centre. Kistler®

piezoelectric multi-

component dynamometer has been used to measure the

cutting forces under different conditions. The surface

roughness has been measured with the help of Taylor

Hobson Surface roughness instrument. Lastly, the tool

wear is measure with the help of Ziess Stereo Discovery

V.20 microscope. Further details of experiments are

provided in table 3.

Table 3: Machining conditions

Cutting Environment Dry, Dry (Cryo treated

tools), Cryogenic

Cutting Speed (m/min) 40,60,80

Depth of cut (mm) 1

Feed rate (mm/rev) 0.1

Nimonic bar

dimensions (mm) Diameter= 60, Length= 300

4 Results and Discussions

All experiments have been conducted under dry,

cryo treated and cryogenic conditions. Cutting forces,

tool wear and surface roughness have been measured for

all these conditions at different speeds after 60 seconds

of machining. Comparison of all these output

parameters has been presented in this paper. Figure 5

shows the comparison of main cutting force (Fz) for all

3 conditions. At all 3 cutting speed values, dry condition

yielded the highest values of cutting force as compared

to cryo-treated and cryogenic conditions. At both 40

m/min and 80 m/min cutting speeds, the reduction of

approximately 4.5% was observed in cutting force

magnitude with cryo treated condition as compared to

dry condition. Whereas for the same speed levels the

cutting force magnitude was found to be reduced by

10% with cryogenic cooling condition as compared to

dry environment. The reduction in cutting force under

cryo-treated condition was mainly due to the formation

of hard eta phase particles during cryogenic treatment of

the tool which has resulted in an improvement in the

wear resistance capability of the tool. While the

formation of lubrication film during cryogenic cooling

condition could be considered as the possible reason for

cutting force reduction under cryogenic machining. The

reduction in the amount of temperature sensitive tool

wear such as: adhesion wear and diffusion wear during

cryogenic cooling could also be a reason for reduction

in cutting force values during direct cryogenic cooling.

5th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12

Guwahati, Assam, India

Figure 5: Comparison of cutting force v/s cutting

speed under different cutting conditions

The surface roughness was also measur

cases as shown in Figure 6. Surface roughness in case of

cryo-treated tools was found to be almost equal

different cutting speed conditions. Cryogenic cooling

resulted into inferior surface roughness

cryo-treated conditions. At 40 m/min, cryo

outperformed both dry and direct cryogenic condition in

terms of surface finish value. At this condition surface

roughness of 0.66 μm was obtained with indirect

cryogenic method. Whilst surface roughness of 0.86

and 0.99 μm was produced by dry and direct cryogenic

condition respectively. It has also been observed that

with higher cutting speeds of 60 m/min and 80

dry condition provided better surface roughness as

compared to both cryogenic application methods.

Absence of built up edge formation and material

softening due to higher temperature at higher cutting

speed could be considered as the reason for

improvement in surface finish. At all

cryo treatment method outperformed direct cryogen

method in terms of surface finish. As compared to

cryogenic cooling, the surface roughness was improved

by 33%, 37% and 25% with cryo-treated tools at 40

m/min, 60 m/min and 80 m/min respectively. It could be

concluded that workpiece became brittle

with the direct application of liquid nitrogen

cryogenic cooling method which resulted into poor

surface roughness as compared to dry and cryo

conditions.

Figure 6: Comparison of surface roughness

cutting speed under different cutting conditions

350

400

450

500

40 60 80

Fz(

N)

Cutting speed(m/min)

0

0.5

1

1.5

40 60 80

surf

ace

rou

gh

ne

ss( μμ μμ

m)

m)

m)

m)

Cutting speed(m/min)

All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12

Figure 5: Comparison of cutting force v/s cutting

speed under different cutting conditions

The surface roughness was also measured for all 3

Surface roughness in case of

ools was found to be almost equal the 3

ryogenic cooling

inferior surface roughness than dry and

, cryo-treated tool

outperformed both dry and direct cryogenic condition in

terms of surface finish value. At this condition surface

was obtained with indirect

surface roughness of 0.86 μm

dry and direct cryogenic

It has also been observed that

with higher cutting speeds of 60 m/min and 80 m/min,

better surface roughness as

both cryogenic application methods.

up edge formation and material

softening due to higher temperature at higher cutting

speed could be considered as the reason for

inish. At all cutting speeds,

method outperformed direct cryogen

ace finish. As compared to

cryogenic cooling, the surface roughness was improved

treated tools at 40

m/min, 60 m/min and 80 m/min respectively. It could be

concluded that workpiece became brittle and hardened

application of liquid nitrogen in direct

which resulted into poor

to dry and cryo-treated

e 6: Comparison of surface roughness v/s

cutting speed under different cutting conditions

Flank wear of cutting insert was measured with the

help of Carl Ziess microscope for each

60 sec of machining. Figure 7 shows the flank wear

images for all the 3 conditions at 40 m/min.

found that tool wear in dry condition was

direct and indirect cryogenic condition

Figure 8. At 40 m/min, the flank wear value

µm, 37.32 µm and 34.26 µm was observed with dry,

cryo-treated and cryogenic condition

cryo treatment and cryogenic cooling

method increased the tool life by 30% and 36%

respectively over dry cutting at lower speed level.

higher cutting speed of 60 m/min and 80 m/min,

cryogenically treated tools performed slightly better

than untreated tools used in dry c

improvement of approximately 8% has been observed

with cryo-treated tools over dry

cutting speeds. The improvement observed in the tool

life of cryo-treated inserts was mainly due to the

changed microstructure. Rise in cuttin

temperature could be the possible reason of early tool

failure under dry cutting condition. As compared to dry

and treated tools, the better tool life has been observed

with direct cryogenically cooled tools.

speed of 80 m/min, direct cooling has shown a tool life

improvement of 90% and 77% as compared to dry and

indirect cryogen methods respectively. Possibly a

drastic reduction in cutting tool temperature

the cryogen has resulted in such improved behaviour.

(a)

(c)

Figure 7: Flank wear at 40 m/min under all 3

conditions (a) Dry cutting condition (b) Indirect

cryogenic condition (cryo-treated tool

cryogenic condition

Cutting speed(m/min)

Dry

Cryo-treated

Cryogenic

Cutting speed(m/min)

Dry

Cryo-treated

Cryogenic

All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT

108-5

was measured with the

iess microscope for each condition after

Figure 7 shows the flank wear

at 40 m/min. It has been

dry condition was more than

direct and indirect cryogenic conditions as shown in

the flank wear values of 54.07

m was observed with dry,

treated and cryogenic conditions respectively. Both

cooling application

the tool life by 30% and 36%

respectively over dry cutting at lower speed level. At

higher cutting speed of 60 m/min and 80 m/min,

cryogenically treated tools performed slightly better

ools used in dry cutting. An

8% has been observed

eated tools over dry condition at higher

The improvement observed in the tool

treated inserts was mainly due to the

changed microstructure. Rise in cutting zone

temperature could be the possible reason of early tool

failure under dry cutting condition. As compared to dry

and treated tools, the better tool life has been observed

cooled tools. At a cutting

cooling has shown a tool life

improvement of 90% and 77% as compared to dry and

methods respectively. Possibly a

reduction in cutting tool temperature because of

resulted in such improved behaviour.

(b)

Figure 7: Flank wear at 40 m/min under all 3

conditions (a) Dry cutting condition (b) Indirect

treated tool) (c) Direct

cryogenic condition

Effect of Direct and Indirect Cryogen Application Methods on the Turning Forces, Tool Wear and Surface Finish of a Nickel Based Alloy

(Nimonic 90)

108-6

Figure 7: Comparison of Flank wear v/s cutting

speed under different cutting conditions

5 Conclusions

Cutting force, surface roughness and tool wear have

been measured under dry, indirect and direct cryogenic

environment for machining of Nimonic 90 bars. The

major conclusions that can be drawn from the

experimental results are as follows:

1. Cryo-treated cutting tool inserts outperformed

untreated inserts under dry cutting condition in terms of

cutting force, surface finish and tool life at the selected

cutting speed levels.

2. Direct cryogenic application has also emerged as a

better cutting environment for the sustainable machining

of Nimonic 90 alloy.

3. From surface finish point of view the cryo-treated

method yielded better results as compared to dry and

direct cryogenic condition.

4. Overall both direct and indirect cryogenic methods

are found to be better than dry cutting approach. These

methods are not only eco–friendly but also save the cost

of machining by increasing tool life. Therefore, using

cryogenic approaches one can bring sustainability to the

metal cutting process.

Acknowledgement

The Authors want to greatly appreciate the help

rendered by Dr. Jagtar Singh (Associate Professor in

Mechanical Engineering Department) of SLIET

Longowal, for providing cryogenic treatment facility.

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0

100

200

40 60 80

Fla

nk

we

ar(

μμ μμm

)m

)m

)m

)

Cutting speed(m/min)

Dry

Cryo-treated

Cryogenic