r lssN 1411_1284 F
Effect of Cutting Parameters on Surface Roughness of AISI D2 in Turning :, Using Coated and Uncoated Carbide Tools
C.H. Che
Haronr,
J. A.
Ghanir,
G.A.
lbrahim2, y. Burhanuddin2
and A.
yasir3 I Mechanics and Material Department of National University of Malaysia 2 Mechanical Engineering Department of Lampung University I Mechanical Engineering Department of Kuala iumpur University D2 isAbstsutrdaicetd--t-oSuirnf'vaecsetigroautgehtnheesseofffetocotlostfeecluAttiInSgI
parameters (cutting speed, feed rate and
coating)
on surface roughness
at various machining parameterc. tools
(K 313) were used in turning tool steel AISI D2
Coated cerbide tools (KC 9125) and uncoated carbide
bar with hardness of
267 ll\t.
Machining tests were performed in
dr-v
cutting condition at various cutting speeds and feed rates while the depth
ofcut
was kept
constanl
Taguchi's design of experiment
with
accommodate the machining
prrameters
of various
standard orthogonal ai-ray L12 was cmployed to
cutting speeds and feed rates. Coating
cutting speed and feed rate
inlluenced
the surface roughness
values surface roughness
is
the feed rate, for both {ypes of but the main factor thst grve
a significant effect on the cutting
tools. The
high cutting speed and low feed rate
produeed * low
surface roughness
vrlue.
The lowest surface roughness value for
uncoated anil coated
carbide tools were
recorded
at
a combination
of
the cutting speed of
250
m/min and the feed rate of 0.05
rr,m/put Generally, coated carbide toots with low feed rate performed better than uncoated carbide tools. Keywords --- AISI D2, carbide tcol, surface roughness I. hITRODUCTIO}{
the metal-working industry and provide the best
Coated and
uncoatcd
carbides are widely used in
integrity as finished machining
becomes
more critical,
altemative for most tuming operations. Study on surface
mainly, to' produce a high
qualif
of mechanical components
[,3].
Now,
Requirements
on satisfied surface integrity
are
not only based on surface roughness but also focused on
macrostrucfure, microskucture, micro hardness, residual stress and fatigue life.
critical in view of very high demand for performance,
The quality of machined surface becomes more
safety, lifetime and reliability. The components that are
applied in high stress and temperature surrounding-
used in automotive, aerospac€ and other induskies are
Hence, the surface
integrity
of
mabhined
components become more important because it will cause sudden fatigue failure, therefore further research and development on machined surface
ofhard
steel components are highly required.
Smoother surface roughness arc usually obtained with lure grained size and hardness of tool, it will also increase with increasing grain density [17J. role in determining a surface roughness quality. The Selecting a machining process plays an important surface roughness Phenomenon such as over-hea! micro
9th lnt'l QIR Proceeding, 6-7 Sept 2006
IMM-34 crack, residual shess, fatigue life and plastic deformation, are
caused by thermal mechanic, transposed phase, changed microstructure,
melted and redeposited layers, apperared on machined surface. In this paper, tuming processes were carried out io investigate the influence ofcutting pararneters
on surface integrity of AISI D2 tool steels
and to find optimum condition. II. EXPERIMENTALMETHOD A. Machining Test
Milacron Avenger 200T
Tuming cenrcr
in a dry cutting
Machining tests was performed on a Cincinnati
condition at various cutting speeds and feed rates while the depth of cut was kept constant at 0.15
mrn.
A 5 mm precut
entr5r
phase is
ma,le
in order to obtain a smooth initial wear by avoiding concentrated impact
toad,
which could trigger chipping at
rhe treginning of
the
machining process.
The test was stopped when
Vp*
reached 0.6 mm for uncoated
carbicie
tools, and 20
minutes
of cutting time
were measured
for
each various cutting parameters using
for coated carbide tools. Surface roughness
ofR"
and R
,- lv{itutoyo Surftest-SJ 301 after each cutting. The data are plotted in graph cutting length versus surface roughness. B. Wcrk
piece Material and
Cuuing
Tool Material. The work piece material used in this study was
been fully annealed. The work piece material rvas
AISI D2 tool steel with a hardness of
25
HRC and it has
prepared in
the
form of 330 mm x 100 mrn bar. Table I and
show the chemical composition and physical
2
properties of AISI D2 respectively. TABLE
I
CHEMICAL COMPOSITION OF AISI D2 TOOL STEEL (% WT)
TABLE 2 PHYSICAL PROPERTIES OF AISI D2 TOOL STEEL
(cWonmd"uCc)t (YK"gTmtY-)Ha(rt-loYne)ss (MNo/mdmu2lu)s(JH/k"gu"tC) There are two rypes of carbide tools used in this study i.e. coated and uncoated carbide tools. The ISO Page 1 of 5 .*. designation for these carbide tools is CNMG 120408. The chemical composition of uncoated carbide tools is shown in Table 3. TABLE 3 CHEMICAL COMPOSITION SUBSTRATE CARBIDE TOOLS ('/o WT) Co CrrCr 6.0 0.5 WC 93.5 The CVD coated carbide tool (KC 9125) has three layers of TN, Al2O3 and TiCN as under, intermediate and outer layers, respectively. The inserts were rigldly mounted on a tool holder with an ISO designation of MCLNR-2O2OKI2 ND4. C. Design of experiment orthogonal anry Lp Taguchi's design of experiment with a standard orthogonal array L12 was used because of its minimum number of required experimcntal trials and yet gave satisffing results. Twelve experiments with a combination of different cutting parameters were randomly repeated. Three levels ofcutting speeds and two levels offeed rates were tested. The depth of cut and rake angle were kept constant at 0.15 mm and 0"
respectively. Factors and levels used in the experiment are shown in Table 4. TABLE 4 FACTORS
A].ID
LEVELS USED IN THE
EXPEzuMENT
Factors
Cutting speed (mnv'min) l-eed
rate (mm/rev)
DeptJr
of cut (mm) Rake angle
(") t50 0.05 0-15 0 Levels 200 2so 0.10 III. RESULTS AND DISCUSSION A. Effect ofCoating on Surface.Roughness Fig. I shows that the surface roughness values at the cutting speed of.200 mrhin and at the feed rate of 0.05 mmlput for uncoated carbide tool were higher that coated carbide tool. For uncoated carbide tool, the surface roughness increased dranratically and maximum cutting length was 0.863 km at the surface roughneSs of L6l pm. In addition the surface roughness increased gradually, and cutting length was 4.090 km. It can be revealed that the its value for coated carbide tool was only 0.68 pm at the coating layers can reduce the surface roughness value. The coating layers on the cutting tool can reduce the heat tssN 1411-12U , generated on tool edge 3nd- also decrease iriction between the cutting tool and workpiece materials (Ezugwq 1997; Che Harorl 2001)- Similar results are also found for the cutting speed of 150 m/min and 250 m/min. It can be concluded that the coaiing layers on the cutting tools gave a significant effedt on thc surface roughness, whether at low or high cutting speed from this experiment. Further machining will produce a gradual increase ofthe surface roughness until the coating layers flake fiom the cutting tml- , Graph cnttirU length.\,s surfac€ rcWhness cs = 200 mrmin t.&, 1.GO .-l 112'&O IEdt*00..q, E 0..0 5 o:o , 0.00 Fig- l. The graph of cutting length against surhce roughness for coated and uncoated carbide tools at feed rate of 0.05 nudpul .: i . ,: , i cutting tool was sig4ificant at the feed.rate of 0.10 .Iig.2 shows.the effept of .coating layers.of the mm/put and the cutting speed of 200 rn/min. For the .uncoated carbide tool,, the. surface roughness value reached 2.2 pm with the cutting length of 0.683 kn. This surface roughness was higher than the surface roughness of the coated rarbide tool which has 1.48 pm with the cutting Iength of 5.200 km. It means that the coating layers such as TN, TiC and TiCN on rhe cutting tool can inciea-"e the tool life or reduce the surface roughness as influenced by reducing the friction betweeri cutting tool and workpiece materials (EzugwrL 1997; Che Haron 2001 ). For both levels of feed rate of turning AISI D2, the coated carbide tools produced a surface roughness better than
uncoated carbide tools,
so
it can be
recommended
that
usirrg
coated carbide tools
rvhen machining tools 2001; Rech & Moison, 2002). Another researcher also steel was better (Boothroy( 1989; Kalpakjian & Schmid, investigated that the coating layers could produce a smoother machined surface roughness, more efficient machining operation and reduced the number ofrejected products (Gerard, 2003).
9th lnt'l QIR Proceeding, 6-7
Sepi
2006
IMM-34
Page 2 of 5
i d I tssN 141't-1284 Graph cutting lengith vs surface roughness cs = 250 m/min E!I- 2211....0505 lIpt* It arclrnocaotaei"od 1I # € 0.5 Culire lsB0r 0an) Fig- 2. The graph ofcutting length against surface roughness for coated and uncoate.d
carbide tools at feed rate of 0.10
mmiput B. Effect ofCutting Speed on
Surface Roughness with
different
cutting speed
at the
feed
rate
of 0.05
There are three curves oi uncoated carbide tools mm/put
as shown in Fig.3.
Generally,
the cutting speed of
value but it is not so. significant. These results were uncoated cartide tools influenced the surface roughness similar to previous researchers who clamed that increase in the cutting speed gave a lower surface roughness (Thomas & Beauchamp,2A0 ; Kopac etal., 2002). The increase of cutting speed gave a little bit cffect on the sui'face rougirness, mainiy at initiai stage and low cufting speed. For all cutting speeds, the surface roughness was at range of 0.6 to 0.7 pm was reached by alrnost the sarire of cuuing length about 0.4 km. For
the cutting speed of 150
rru
'min and
200 m/rnin,
the
surface roughness increased gradually until the end of machining, but for
the cutting speed of
250
m/min, at
initial
stage,
its value also increased gra-dually and then kept constant. Further the cutting tool reach-s wear and then the surface machining will produce a constant surface roughness until roughness increase iapidly until cutting tool fracture. Grapfi cutting length vs surface roughness f = 0.05 mmlptrt 2.70 2-10 -g€ 2l..a1o0 E r.so El,, I o-eo €d oo..o:oo tlttl 0-00 la.r'lr II o..r 0.6 0,8 I r Cfrirq rsqt (km, l2 Fig. 3- The graph shows three types of cutting length verses surface roughness
of uncoated carbide tools
al various
cutting speed
The Fig. 4 strows tiuee curves for
coated carbide tools
that operate
at
the
feed rate of 0.10 mm/
put and the cutting speed o-f l5O 200 and 250 nvmin. Generaiiy, the curves show almost a similar trend line with uncoated cartride tools in Fig.3. At initial stage, tl're surface roughness values for ail cutting speeds were a range of0.4 to 1.5 pm or the cuting length were about 0.2 lon. The surface roughness for low cutting speed of I50 m/min went up consistently until the end of machining operation, meanwhile for higher cutting speed of 200 and 250 rnlmiq the surface roughness little bit reducod and then remained stable. The decrease of machined surface roughness of rrortpiece materials at high cutting spee{ was due to few heats generaled conducted to workpieee materials. Most of heat generated carried away by chipping(Thcmas & Beauchamp, 2003). Another reason encotraged to form plastic deformation to produce was caused by the high temperahue at primary shear zone chipping. Because of increase of the plastic deformation, the cutting at high speeil reduces requirement fbrce to carried aw'ay chipping. Graph cutting length vs surface roughness I = 0.10 mm/put /c.! 4.0 3.s i a-o a E ,.u a +a. BP zt..5o tl' ^i"^ t^ rrrar lr 3 1.0 lcs = i50 nr/min a o.s f 0.0 ^[r^l ' lccss == 220500 mrn//mmiinn 0.4 Cdire HEfr {}rnl [ig. 4. The graptr sho-ws t]ree types of cutting length verses surface roughness ofcoated carbide tools at various cutting speed C. Effect ofFeed Rate on Su{ace Roughness Fig. 5 shows the surface roughness of uncoated carbide tools at the feed rate of 0.05 mm/put were lower than at the feed rate of 0.10 mm/put. This experiment took place at the same cutting speed of 250 m/min. At the feed rate of 0.05 mm/puq the surface roughness was 0.77 pm with the cutting length of 0.680 km, while at the feed rate of 0.10 mm/put, the surface roughness recorded 2.20 pm with the same cutting length. This value shows that the feed rate gave a significant effect on the surface roughness values. With increasing the feed rate twice, the surface roughness can be increased by more than three times. This results similar to theory, if the feed rate value increased, the surface roughness will decrease (Axinte, 2002). It's because, at the higher feed rate, the tool edge affirmed wear faster and can be done dull. Further rnachining will result in the surface roughness increase gradualty until the cutting edge reach maximum wears and then fails. 9th lnt'l QIR Proceeding, 6-7 Sept 2006 tMM-34 Page 3 of 5 tssN 1411-128r' Fig. 5 can also show a rapid increase of the surface roughness at the feed rate of 0.10 mmiput It happened until the cutting length of 0.3 km. It was probably due to the bigger force on the cutting edge. The same hend line curve was also found in different cutting specds of 150 m/min.and 200 m/min. It clearcd that the feed rate was one of .the nrain factors that influenced the machined surface roughness of AISI D2 with using carbide tools. GEph c'lrttir€ length vs surfiace roughness cs= 250 m/min Graph cutting length vs surhce roughness cs = 250 m/min '2.5 io IrI I E. I I tis Fms mmffil 3 t.o I €E o.s 1t <)acoo l!!.10 mmrput I . 0.0 - r Fig. 5- The graph ofcutting length against surface roughness for diflerent feed rate and uncoated carbide tools. Similar results to uncoated carbide tool were also found in coated carbide tool, the surface roughness values at a feed rate of 0.10 mm/put rilere higher than at the feed rate of,0.05 mm/put as iho*n in Fig. 6. There was a significant difference of the surface roughness values at the cutting speed of 250 m/min between high and low feed rates. Wtrether for the feed rate of 0.05 mm/put or the feed rate of C.10 mm/put showed an increase gradually from inifial stage untii final stage. For the feed rate of 0.05 mm/pu! the suiface roughness at initiai cutting was 0.39 trr.m and at final cutting was l.16 pm, meanwhile for the feed rate of 0.10 mnc/pug 'Jre surface roughness at initial cutting wa! 0.80 pm and at final cutting was 1.48 pm. there q'ere gradual and stable surface roughness values as long as the e*periments were carried out Further machining, the surface roughness values at a feed rate of 0.05 mm/put will be'higher than the feed rate of 0.10 mr,-/put. These results arc stable until the cutting edge fracture. roughness was''more gradual as compared to uncoated . The increase of the coated carbide tool surface coated carbide tool as shown in Fig. 5 and Fig.6, respbctively. It was cau.sed by coating on flank of cutting .tools. The coating layers reduced friction between the cutting tbol and machined surface and t reduced heat generated on cutting edge. o.o 2.O 4.0 6.0 Cueto bngth (km) Fig. 6. Ihe graph ofcutting length against surface roughness for different feed rate and coated carbide tools- D. Efect of Cufiing Speed and Feed rate on Sudace Rougl'ness The lowest surface roughness values for uncoated and coated carbide tools were recorded at a combination of a cutting speed of 250 mimin and a feed rate of 0'05 mm/put The highestcutting speed prcduced a low surface roughness and the iowest feed rate also produced a low surface roughness. High cutting speed and low feed rate was good choice for trrning AISI D2 by using carbide tools. This results is similar to the previous research that of the l0west surfacc roughness of machined surface was found by a combinatiou oflow feed rate and high cutting speed (Thomas & Beauchamp, 2003; Che Haron,200l). IV. CONCLUSION l. Coated carbide tools produced a surface rougtrnes:, which was, befer than uncoated carbide tools in turning AISI D2. Ths coating layers on the cuttir,g tool reduced the friction bet,rreen cutting tool and 2. machined surface. The surface roughness of carbide tools decreased with increase df the cutting speed. The high dutting speed could reduce vibration of work piece material 3. and moit heat generated carried arvay by chipping. The feed rate was a main factor that could give a sigrrificant effect on the suface roughness values, selected low feed rate produced better surface a 4. roughness. The lowest surface roughness values for uncoated and coated carbide tools were recorded at a combination 'of a cutting speed of 250 m/min and feed rate of a 0.05 mm/put. 9th lnt'l QIR Proceeding, 6-7 Sept 2006 rMM-34 Page 4 of 5 REFERENCES [l] Axinte, D.A- and Dewes, R.C. (2002), *Surface integrity of hot work tool steel after speed milling- experimental data and empirical model", Joumal
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