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CHAPTER 3
EXPERIMENTAL PROCEDURE
The objective of this study is to evaluate the performance of cermet
tools which is subjected to either plain, coated, cryogenically treated. In order
to evaluate these following experimental procedures followed.
3.1 CUTTING TOOL INSERTS
Machining tests were carried out using different cermet cutting
tools on a precision lathe (Venus, Model-SU4) having 18 spindle speeds and
18 table feeds with a maximum speed of 2500 rpm whose specification is
listed in Table 3.1. Cermet cutting tools were used for this study which is
subjected to various conditions and their notations used as described below:
1) Plain cermet without Ti-Al-N coating (UC) and without
Cryogenic treatment (UT) – (UC&UT)
2) Cryogenically treated (T) and uncoated tool (UC) – (UC&T)
3) Ti-Al-N coated cermet (C) without cryogenic treatment (UT)
– (UT&C)
4) Cryogenically treated and subsequently Ti-Al-N coated (T&C)
and
5) Ti-Al-N coated and subsequently cryogenically treated cermet
(C&T).
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Element composition details of cermet cutting tool using XRF is
shown in Figure 3.1. The element composition details and specifications of
the cutting tool inserts are presented in Tables 3.2 and 3.3 respectively. TiC
based cermet (TTI15 grade) cutting tool inserts from WIDIA Inc.with ISO
P-10 grade cermet rhombic flat inserts of ISO specification CNMG12040822
are used for this study. The Machining was performed using WIDAX tool
holder with ISO specification PCLNR 1616 K 12 fitted with one insert. The
image and specification of the cermet insert and tool holder assembly are
shown in Figures 3.2 to 3.4 respectively.
Table 3.1 Lathe specifications
Specifications Dimensions
Model Venus (SU4)
Bed Length 5+1/4’ and 6’
Bed Width 11"
Center Height 9"
Spindle bore 54 mm
Horse power of the motor 3 HP
Number of speeds 18 (45Rpm - 2500 Rpm)
Number of feeds 18 (0.025 mm/rev – 0.99 mm/rev)
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Figure 3.1 Element composition details of cermet cutting tool using XRF
Table 3.2 Element composition details of cermet cutting tool
Elem. Line Mass[%] 2sigma[%] Intensity[cps/mA]
22 Ti K 65.78 25.83 30.46
23 V K 0.11 5.19 0.07
27 Co K 20.75 21.92 9.75
28 Ni K 13.37 19.76 7.13
Table 3.3 Details of cutting tool inserts specifications
Cutting tools
rakeangle
clearanceangle
inclinationangle
plan approach
angle
Includedangle
nose radius
( ) ( ) ( ) ( ) (er) (re)
Parameter -6 6 -6 95 80 0.8 mm
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Figure 3.2 Photo image of the cutting insert used
Figure 3.3 Cermet insert specification details
Figure 3.4 Image of the cutting tool holder assembly
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3.2 CRYOGENIC TREATMENT
The cermet tools are subjected to cryogenic treatment either in
plain condition or with or without Ti-Al-N coating for this study. The
cryogenic treatment cycle is given in Figure 3.5, which consists of following
stages:
(i) a gradual lowering of temperature to -195°C
(ii) holding for 18 h, and
(iii) then subsequently raising temperature back to room
temperature.
The cryogenic treatment was carried out by Cryoking processor,
CRYOKING Inc. Whose specification is given in Table 3.4.
Table 3.4 Specifications of cryogenic processor
Specifications Details
Model Cryoking
Cryogenic temperature range up to -250º C
Maximum Weight of Materials can be treated 500 Kg
Controlling Method (Temperature Control ) PLC based
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04080
120160200240280320360
0 6 12 18 24 30
Time (Hours)
Cryogenic Treatment Schedule
Figure 3.5 Cryogenic treatment cycle
3.3 Ti-Al-N COATING
Tool wear is inherent in machining. There are many steps and
measures taken to reduce the level of tool wear on cutting tools. One of the
steps is applying surface treatment on the base cutting tool material.
A popular method is applying coating onto the base cutting tool material by
the use of PVD method. The TiAlN coating provided on the cermet cutting
tools by Overlooks Balzers Coating India Ltd with the commercial name of
“BALINIT®FUTURA NANO” using INNOVA, a new-generation coating
system.
In arc evaporation (Figure 3.6) an arc is struck between the backing
plate (anode) and the coating material (cathode). The arc moves over the
coating material and evaporates it. Due to the high currents and power
densities employed, the evaporated material is ionised to a high degree
Ascend Soak Descend
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reactive gas and metal ions hit the component surface and are deposited there
as the coating material.
(Courtesy, Oerlikon Balzers Inc.)
Figure 3.6 Arc evaporation process
1. Argon
2. Reactive gas
3. Arc Sources (coating material and backing plate)
4. Components
5. Vacuum pump
Tools are placed in a processing chamber, which is pumped down
to produce a vacuum. The cermet tools are coated with Ti-Al-N whose
specification of the coating is listed in Table 3.5.
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Table 3.5 Properties of BALINIT®FUTURA NANO coating
Properties Units BALINIT® FUTURA NANO
Coating material Ti-Al-N
Micro hardness (HV 0.05) 3300
Coefficient of friction against steel (dry) 0.30 – 0.35
Coating thickness m) 4
Residual compressive stress (GPa) -2.0
Maximum service temperature (°C) 900
Coating temperature (°C) < 500
Coating colour violet-grey
Coating structure Nano - structured
3.4 WORK MATERIALS
The work materials used in these machining studies were AISI
4340 steel (also known as EN 24 steel) and AISI D2 steel (also known as Die
steel) which were hardened to a hardness value of HRC 45 and HRC 50
respectively. The work piece materials used for the machining studies and
their hardness after heat treatment are given in Table 3.6. As per ISO 3685
(1993) the work pieces selected in the present study has the dimensions of 50
mm diameter and 375 mm length, so that L/D ratio should not exceed 10 ,in
order to assure the necessary stiffness of the elastic fixed system
chuck/piece/cutting tool .
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Table 3.6 Work piece materials and their hardness after heat treatment
Sl.No Work piece Material Hardness after heat
treatment 1 AISI 4340 steel HRC 45
2 AISI D2 steel HRC 50
3.4.1 AISI 4340 Steel
AISI 4340 steel is Nickel-Chromium-Molybdenum high tensile
steel. It has good wear resistance and shock resistance and it is characterised
by high strength and toughness. The hardened and tempered AISI 4340 steel
can be further surface hardened by flame or induction hardening and followed
by Nitriding. It is mostly used in industrial sectors for applications requiring
high tensile/yield strength. The typical applications are heavy duty shafts,
gears, axles, spindles, couplings etc. The AISI 4340 steel hardened by heat
treatment of quenching followed by tempering at 845°C and 440°C.
AISI 4340 steel is regarded as readily machinable, and operations
such as turning, milling and drilling etc. can be carried out satisfactorily.
Some of the related specifications of AISI 4340 steel are EN 24, BS 970
817M40, SAE 4340, 40NiCrMo6 etc. The chemical composition of AISI
4340 steel is given in Table 3.7. The microstructure and EDAX analysis of
AISI 4340 steel (HRC 45) are presented in Figure 3.7 and 3.8 respectively.
Figure 3.7 reveals the presence of carbide particles in the Fe matrix.
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Table 3.7 Composition of AISI 4340 steel by weight percentage
Composition C Si Mn Cr Mo Ni
(Wt %) 0.38- 0.43 0.2-0.35 0.65-0.85 0.7 – 0.9 0.2-0.3 1.65-2.0
Figure 3.7 Optical micrograph showing the microstructure of hardened AISI 4340 steel (HRC 45)
Figure 3.8 Electron dispersive X- Ray analysis (EDAX) of AISI 4340 steel
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3.4.2 AISI D2 Steel
AISI D2 is a high-carbon, high-chromium tool steel alloyed with
Molybdenum and Vanadium characterized by high wear resistance, high
compressive strength, good through-hardening properties, high stability in
hardening, and good resistance to tempering reported by Arsecularatne et al
(2006). AISI D2 steel is one of the most widely used steel in the industry. The
chemical composition and EDAX analysis of AISI 4340 steel is given in
Table 3.8 and Figure 3.9 respectively. AISI D2 steel is recommended for tools
requiring very high wear resistance, combined with moderate toughness
(shock-resistance). The AISI D2 steel hardened by heat treatment of
quenching followed by tempering at 1050°C and 530°C respectively.
Table 3.8 Composition of AISI D2 steel by weight percentage
Composition C Fe Mn Si Cr Mo V
(Wt %) 1.4-1.6 rema 0.6 0.6 11-13 0.7 -1.20 1.10
Figure 3.9 Electron dispersive X- Ray analysis (EDAX) of AISI D2 steel
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3.5 EXPERIMENTAL CONDITIONS
Machining studies were conducted on hardened AISI 4340 steel
and AISI D2 steel using the above mentioned cermet cutting tools at different
cutting conditions. Experimental conditions are shown in Table 3.9 and 3.10.
For AISI D2 steel machining, the lower and higher cutting conditions are
considered, because the middle cutting condition may not be significantly
varied. The comparison was carried out in terms of the performance of the
different processed cermet tools while machining AISI 4340 steel and AISI
D2 steel respectively.
Table 3.9 Experimental conditions for AISI 4340 steel
Cutting speed m/min 115, 140, 180
Feed rate mm/rev 0.06,0.08,0.12
Depth of cut mm 0.1,0.15,0.2
Environment Dry
Table 3.10 Experimental conditions for AISI D2 steel
Cutting speed m/min 75, 92, 118
Feed rate mm/rev 0.06,0.12
Depth of cut mm 0.1,0.2
Environment Dry
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3.6 OBSERVATIONS
The main objective of the present study is to evaluate the
performance of different cermet cutting tools on machining AISI 4340 steel
(HRC 45) and AISI D2 steel (HRC 50). The performance of the cermet
cutting tools was evaluated by i) Measurement of flank wear ii) Measurement
of surface roughness on work materials iii) measurement of cutting forces iv)
Microscopic studies on worn out tools and chips of the work materials.
The wear measurements were taken using a Tool Makers Microscope
(Metzer-model METZ 1395) with 30X magnification factor. The machining
time was accurately measured with a stopwatch. The machining was stopped
periodically to measure tool wear and surface roughness of the work
materials. The surface roughness (Ra) values were obtained by moving the
stylus of the surface roughness measuring instrument (TR 200) on the work
material. The specification of surface roughness measuring instrument is
given in Table 3.11.
The cutting force components were measured during turning using
strain gauge type dynamometer with a sensitivity of 1 Newton. The
metallographic microstructure of cutting tool was obtained according to
ASTM B 390-92 (2000). Scanning Electron Microscope (FEI ESEM Quanta
200) was used to study the wear of worn and microstructure of the tool
materials. The electrical resistivity of the cryogenically treated and untreated
types of cutting tool inserts used in this study was measured with a standard
four probe set-up (Four probes Resistivity Instrument, Concord, India) and the
average values of electrical resistivity were evaluated.
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Table 3.11 The specification of surface roughness measuring instrument
Specifications of TR200 Surface Roughness Tester
Model Name TR200 Surface Roughness Tester –TIME make
Roughness Parameters
Ra, Rz, Ry, Rq, Rt, Rp, Rmax, Rm, R3z, S, Sm, Sk, tp
Profiles Measured Primary profile (P), Roughness Profile (R) tp curve (Mr)
Measurement Accuracy < ±10%
Max Tracing Length 17.5mm
Detector Standard model TS100, inductive, Diamond tip radius 5microns
Power Li-Ion Battery Rechargeable
Battery Capacity 1000mAh (>3000measurements)
Charger 220V/110V, 50Hz
Working Temperature 5 to 40 degree C
Dimensions 141mmx56mmx48mm