60 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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60
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