Author'sAcceptedManuscript Effect of cutting conditions on wear perf or- mance of cryogenically treated tungsten car- bide inserts in dry turning of stainless steel Nursel Altan Özbek, Adem i!ek, Mahmut "#lesin, $nur Özbekww w%els e&ie r%comlocatetriboint ())* +.-/0123. 45//-0 6$)* h tt p*''d7%doi%org'. % ../'8%triboint%9. 4%:%9; <eference*=><)-:, . >o appear in* >ribology )nternational <ecei&ed date* 9; April 9.4 <e&ised date* 9; =uly 9.4 Accepteddate* .9 August 9.4 ?ite this article as* Nursel Altan Özbek, Adem i!ek, Mahmut "#lesin, $nurÖzbek, Effect of cutting conditions on wear performance of cryogenically treated tungsten carbide inserts in dry turning of stainless steel, >ribology )nternational, ht t p*''d7%doi%org'.%. ./'8%triboint%9.4% :%9; >his is a (6@ file of an unedited manuscript that has be en accepted forpubl icati on% As a ser&ice to our customers we are pro&i ding this early &ersion of the manuscript% >he manuscript will undergo copyediting, typesetting, and re&iew of the resulting galley proof befo re it ispu bl ish ed in its final citable form% (lease note that during the prod uc tion process errors may be disco&ered which could affect the content, and all legal disclaimers that apply to the 8o urn al per tai n%
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<ecei&ed date* 9; April 9.4<e&ised date* 9; =uly 9.4Accepted date* .9 August 9.4
?ite this article as* Nursel Altan Özbek, Adem i!ek, Mahmut "#lesin, $nur
Özbek, Effect of cutting conditions on wear performance of cryogenicallytreated tungsten carbide inserts in dry turning of stainless steel, >ribology)nternational, h t t p*''d7%doi%org'.%../'8%triboint%9.4%:%9;
>his is a (6@ file of an unedited manuscript that has been accepted for
publication% As a ser&ice to our customers we are pro&iding this early &ersion
of the manuscript% >he manuscript will undergo copyediting, typesetting,
and re&iew of the resulting galley proof before it is published in its final citableform% (lease note that during the production process errors may be disco&eredwhich could affect the content, and all legal disclaimers that apply to the
studied machinability of A)+) ./ austenitic stainless steel using cryogenically treated and untreated ++ twist
drills% E7perimental results showed that tool life of treated drills impro&ed from .;F to 9.:F% >he
impro&ements were mainly attributed to formation of fine and homogeneous carbide particles and tr ansformation
of retained austenite to martensite% Akhbarizadeh et al% performed a study to in&estigate the effects of cryogenic
treatment on wear beha&iour of A)+) 6/ cold work tool steel% >he results re&ealed that cryogenic treatment
substantially reduced the amount of retained austenite in the microstructure and therefore it impro&ed wear
resistance and hardness of A)+) 6/ tool steel% uang et al% reported that cryogenic treatment significantly
changed the microstructure of M9 tool steel% >he e7periments indicated that wear resistance of the tool steel
impro&ed due to facilitating the carbon clustering after cryogenic treatment and increases in the carbide density
after subseGuent tempering process% Hiu et al% claimed that the hardness and abrasion resistance of ?rMnI high-
chromium cast iron could be impro&ed ob&iously due to the precipitation of carbides, the mar tensite
transformation, and a refined microstructure resulting from cryogenic treatment%Cang et al in&estigated the
effects of deep cryogenic treatment on the microstructure, hardness and abrasion resistance beha&iours of
./?r.Mo.?u cast iron sub8ected to destabilization treatment% >he results showed that the cryogenic treatment
can effecti&ely reduced the retained austenite after destabilization heat treatment, but could not make r etained
austenite transform completely% ?ryogenic treatment can markedly impro&e bulk hardness and abrasion
resistance of the high chromium cast iron% "ill et al% aimed to present the metallurgical and mechanical
characterization of cryogenically treated tungsten carbide 3C?J?o5 in terms of K-phase particles and wear
beha&iour% >hey declared that the hard phase particles of tungsten carbide were refined into their most stable
form &ia the phenomenon of spheroidization after shallow 3-.. D? for .: h5 and deep 3-.1/ D? for : h5
cryogenic treatment% )t was pointed out that cryogenic treatment caused crystal structure changes in both the hard
and soft binder phases of the tungsten carbide material, which may ha&e been responsible for the enhanced
hardness and wear resistance properties along with the precipitation of K phase carbides% Lao reported that the
abrasi&e wear resistance of sintered tungsten carbide inserts had increased after cryogenic treatment% Iryson
claimed that the wear resistance, and hence increase in tool life, of carbide tools was pro&ided by the
impro&ement in the holding strength of the binder after cryogenic treatment% <eddy et al% in&estigated the
machinability of ?;4 steel with untreated and treated 3-.0/ D? for 9; h5 tungsten carbide )+$ (- inserts in
terms of flank wear, main cutting force, and surface finish% )t was determined that cryogenic treatment resulted in
better machinability due to the increase in the thermal conducti&ity of the tungsten carbide% >his resulted in a
decrease in the temperature of the tool tip during the turning process% adi&el and <udramoorthy e7amined the
performance of cryogenically treated and untreated coated carbide inserts in terms of flank wear, power
consumption, and surface roughness in the turning of nodular cast iron% $n the whole, the cryogenically treated
coated carbide inserts e7hibited a better performance than that of the untreated ones% >his outcome was attributed
to the presence of fine K-phase carbide distribution in the cryogenically treated inserts% ong et al% in&estigatedand analyzed the differences in tool performance between cryogenically treated and untreated tool inserts during
the orthogonal turning of steel% >he authors claimed that treated tools performed best when the tool temper atur e
was kept low and that hea&y-duty cutting operations would not benefit when the cutting tool was heated for long
periods% <am8i et al% reported that cryogenically treated tungsten carbide inserts e7hibited superior wear
performance to untreated ones in turning of gray cast iron at all combination of cutting par ameters%
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+NM" .9;.9 J >@>ool holder * 6+IN<'H 9494 M.9?utting method * $bliGue cutting?utting condition * 6ryeat treatment * ?ryogenic tr eatment?utting speed, c * ., .9, .; and ./ m'min@eed rate, f * %.4, % and %;4 mm'r e&6epth of cut, a * 9%; mm
. E!perimental "esults and #iscussion
21 +icrostructural o$servations
211 +icrostructure analysis
>here are three main phases in the microstructure of C?-?o inserts, namely, the S phase 3C?5, T phase 3?o5,
and K phase 3?oC? and ?o/C/?5% @ig% . shows +EM pictures of the S, T and K phases of the untreated and
treated uncoated inserts% >he K carbides appear as dark gray spots in the microstructure of the carbide inserts%
adi&el and <udramoorthy reported that the cryogenic treatment refined coarser, randomly-distributed K phase
particles into the most stable form% >hese f iner particles along with the larger tungsten carbide particles formed a
denser, more coherent and much tougher matri7% After cryogenic treatment, the fine K carbides impro&ed thehardness and wear resistance without significantly affecting the toughness% $n the other hand, the effects of
cryogenic treatment on S phase grain size of the carbide inserts were noted and in&estigated% Ppon measuring the
size of the particles, it was found that the a&erage grain size was .1%0.4 nm and 9.%;; nm for the untreated and
treated inserts, respecti&ely% <eddy et al% claimed that the cryogenic treatment reduced the chemical degradation
of the cobalt matri7 at higher temperatures% Hower binder contents in tungsten carbide samples increased the
o&erall thermal conducti&ity% An increase in carbide grain size for the cryogenic treated cemented carbides
increased the thermal conducti&ity of cemented carbide% >his effect was attributed to an increase in carbide grain
contiguity and the dominant role of the carbide phase in thermal conduction in tungsten carbide based cemented
carbides%
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>he &ariations of flank wear of both the untreated and treated inserts at a feed rate of %.4 mm're& and cutting
speeds of ., .9, .; and ./ m'min according to the cutting times are shown in @igs% ;a, ;b, ;c and ;d,
respecti&ely% )n the e7periments, the workpiece materials were turned for 9, 9, / and . min at cutting speeds of
., .9, .; and ./ m'min, respecti&ely% As shown in @ig% ;, flank wear appeared at the first stop time and
increased with increasing cutting time at all cutting speeds% Moreo&er, at all combinations of cutting conditions,
the treated inserts e7hibited better peformance than the untreated ones in terms of flank wear% At a feed of %.4
mm're& and cutting speeds of ., .9, .; and ./ m'min, the flank wear formed on the treated inserts had
impro&ed by ;F, ./F, .0F and 90F in comparison with the untreated inserts% >his can be attributed to
impro&ing wear resistance due to increasing hardness and to the impro&ing microstructure &ia precipitation of
secondary carbides and homogenous distribution of the carbide% Microhardness measurements re&ealed that the
microhardness &alues of the treated inserts had increased by /F when compared to those of the untreated inser ts%
>he hardness &alues of the untreated and treated inserts were measured as .01%: and .:.9%/ ,
respecti&ely% $n the other hand, built-up edge 3IPE5 formed on the cutting edges of both the untreated and
treated inserts% Iuilt-up edge freGuently appears in the cutting of ductile materials% )t is well known that
austenitic stainless steels ha&e a high tendency to adhere to the cutting edge of tools due to their ductile structure%
"erth et al% reported that IPE formed on the cutting tools due to ductility and adhesion tendency of austenitic
stainless steels during their turning operations%
)n addition, it can be obser&ed from @ig% ; that the amount of flank wear had increased with increasing cutting
speed% >he flank wear &alue was %../ mm at a cutting speed of ./ m'min and cutting time of . min, while the
flank wear &alue was %19 mm at a cutting speed of . m'min and cutting time of 9 min, thus clearly
indicating the negati&e effects of the cutting speed on flank wear%igher cutting speeds lead to rapid tool wear due to serious heat generation and rapid plastic deformation %
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$ig. '. ariations of flank wear &ersus cutting times at a feed rate of %;4 mm're& and cutting speeds of a5 .
m'min, b5 .9 m'min, c5 .; m'min, d5 ./ m'min%
233 )otch <ear
>he &ariations of notch wear against cutting times at a feed rate of %.4 mm're& and four cutting speeds are
illustrated in @ig% :% At all cutting speeds, it was obser&ed that notch wear had occurred on the main cutting
edges of the carbide inserts% >he treated inserts e7hibited superior performance to the untreated inserts in terms
of notch wear at cutting speeds of . m'min and .; m'min% >he impro&ement percentages in notch wear on
the treated inserts &ersus the untreated ones were .F and ;F, respecti&ely% owe&er, at a cutting speed of .9
m'min, it was determined that the treated inserts showed a .F worse wear performance than the untreated ones
after a turning process of 9 min% +imilarly, at a cutting speed of ./ m'min, the notch wear on the treatedinserts was 0F more than on the untreated ones% At this cutting speed, as notch wear had occurred on both
inserts prior to the final cutting time, a graphic could not be constructed% After a cutting time of . min, the notch
wear &alues formed on the untreated and treated inserts were measured as %.: mm and %.14 mm, r especti&ely%
)n addition, IPE generally formed on the cutting edges of both inserts% )t is known that IPE on the cutting edge
of tools occurs at lower cutting speeds% @ig%0 shows E62 analyses of IPE region% (resence of @e, Ni, ?r, +i,
and Mn on both tungsten carbide inserts is strong e&idence for IPE%
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$ig. (. E62 analyses of IPE and notch regions of the carbide inserts at a feed rate of % mm're& and cuttingspeed of .9 m'min* a5 untreated, b5 treated%
)n general, treated inserts e7hibited better wear performance than untreated ones in terms of notch wear at all
combinations of cutting conditions% owe&er, at only cutting speeds of .9 and ./ m'min, untreated inserts
were superior to treated inserts% >his e7ceptional case can be e7plained by larger IPE% Cear pictures on @ig% 0b
support this claim%
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$ig. ). ariations of notch wear formed on the untreated and treated inserts according to cutting times at a feedrate of %.4 mm're& and cutting speeds of a5 . m'min, b5 .9 m'min, c5 .; m'min%
At a feed rate of % mm're&, e&en though notch wear appeared at lower cutting speeds 3. and .9 m'min5, at
higher cutting speeds 3.; and ./ m'min5, it did not form on the main cutting edges of either the untreated or
treated inserts% ift!i clarified this case with the reduction in IPE tendency owing to the increasing cutting
speed, which leads to higher temperatures in the cutting zone% $ne of the most important reasons of notch wear
is o7idation% >he notch wear may occur by chemical reaction of tool material and o7ygen in the air at the
interface between tool and the atmosphere with the effects of high temperatures% igh $ content at the notch
wear region is a good indicator for o7idation 3@ig% 05% As shown in @ig% 1, it was obser&ed that significant
decreases in notch wear on the treated inserts had occurred in comparison with the untreated ones% $n the other
hand, at both cutting speeds, notch wear started to form on the treated inserts at the first stop time, whereas it
appeared on the untreated ones after cutting times of 4 min and . min at cutting speeds of . m'min and .9
m'min, respecti&ely% At a cutting speed of . m'min, the treated inserts showed a significant impro&ement of
/1F in notch wear in comparison with the untreated ones% +imilarly, at a cutting speed of .9 m'min, the
impro&ement was ;:F% >hese findings showed that the cryogenic treatment and tempering processes had
significantly enhanced the wear resistance of the carbide inserts at medium feeds% )n addition, it was obser&ed
that a small incidence of IPE had occurred on the cutting edges of both the treated and untreated inserts%
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$ig. *. ariations of notch wear formed on the untreated and treated inserts according to cutting times at a feedrate of % mm're& and cutting speeds of a5 . m'min, b5 .9 m'min%
At a feed rate of %;4 mm're&, no notch wear had appeared on either of the inserts at any cutting speed% >his can
be attributed to the increasing temperatures generated in the cutting zone along with the increasing material
remo&al rate at higher feeds% As the feed rate increases, the section of chip increases and conseGuently friction
increases , this lead to increase cutting forces, especially in thrust direction% )t is obser&ed that the region of high
stresses in the thrust direction turns inward as the feed increases, which may result in the increase in
temperatures generated, so the temperature at interface increases % >he higher temperatures reduced the IPE
tendency%
232 Crater <ear
Measurements of crater depth on the rake faces of the untreated and treated inserts are shown in @ig% .% >he
craters of the treated inserts are shallower than those of the untreated ones at all combinations of cutting speeds
and feeds% At a feed rate of %.4 mm're& and cutting speeds of ., .9, .; and ./ m'min, crater wears on the
treated inserts was reduced by 9F, 4F, 49F and 0F in comparison to those on the untreated ones,
respecti&ely% At a feed rate of % mm're&, the treated inserts e7hibited superior performance by impro&ements of
.F, :F, .F and ;/F at cutting speeds of ., .9, .; and ./ m'min, respecti&ely% +imilarly,
impro&ements in crater wear at a feed of %;4 mm're& were 1F, ./F, .F and F at cutting speeds of ., .9,
.; and ./ m'min, respecti&ely% )n terms of crater wear, the treated carbide inserts e7hibited better performance
at lower speeds than at medium and higher speeds% )t is well known that diffusion occurring because of the
higher temperatures at the tool-chip contact area leads to crater wear% @urthermore, one of the most importantreasons for this diffusion is the chemical affinity between the workpiece and tool materials% )n literature, it was
reported that crater wear significantly decreased owing to chemically inert cutting tools and the decreases in
cutting zone temperatures after cryogenic treatment % Another of the most important causes of crater wear is
abrasion% Abrasion is directly related to the hardness and wear resistance of a cutting tool% As mentioned abo&e,
because of the hardness and wear resistance of the cryogenically treated carbide inserts, they e7hibited a superior
performance compared to the untreated ones%
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$ig. 11. +EM pictures of wear on the carbide inserts at a feed rate of %.4 mm're&* a5 untreated, b5 tr eated%
)n the +EM pictures of the inserts used to turn the stainless steel bars at a feed rate of % mm're& 3@ig% .95, it can be seen that the amount of wear at this feed is more dramatic than at a feed of %.4 mm're&% )n particular, notch
wear had reached a ma7imum at this feed while crater wear was greater and deeper than at a feed of %.4
mm're&% )n addition, it was determined that the notch wear had occurred on the end cutting edges of both the
untreated and treated inserts at a cutting speed of . m'min% Although IPE formed on both inserts, the amount
of IPE on the untreated inserts was Guite large when compared to that on the untreated ones% $n the other hand,
the notch wear on the main cutting edges of the untreated inserts was about three times greater than that on the
untreated ones% @urthermore, the IPE and chippings on the cutting edge of the untreated inserts had caused
significant deterioration of the uniformity of their cutting edges% At a cutting speed of .9 m'min, while notch
wear had appeared on the end cutting edges and plastic deformation on the nose of the untreated inserts, these
types of wear were not obser&ed on the treated inserts% (lastic deformation occurs when high pressures 3i%e%
compression5 are e7erted on the cutting edge in combination with ele&ated temperatures% )t leads to the
generation of higher temperatures in the cutting zone, geometric deformation of the insert, and &ariation of the
chip flow on the rake face% >o a&oid this type of wear, turning inserts should ha&e higher hot hardness % <eddy et
al% reported that cryogenically treated tungsten carbide inserts had higher hot hardness than untreated ones% $n
the other hand, the amount of flank wear on the treated inserts was greater than on the untreated ones% )n
addition, notch wear was obser&ed on the main cutting edges of both inserts% At cutting speeds of .; m'min and
./ m'min, no notch wear occurred on either the main cutting edges or end cutting edges of the untreated or
treated inserts because the IPE tendency had decreased as a result of the higher temperatures generated at the
higher cutting speeds %
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$ig. 1%. E62 analyses for crater surfaces of the carbide inserts at a feed rate of % mm're& and cutting speed of .9 m'min* a5 untreated, b5 treated%
%. ,onclusion
)n this study, the effects of deep cryogenic treatment on tool wear were in&estigated in the turning of A)+) ./
austenitic stainless steel with uncoated cemented carbide inserts% )n conseGuence of the analyses and turning
e7periments performed, the findings obtained in this study are as follows*
V As a result of image processing analysis, it was found that the amount of fine K carbides in the deep
cryogenically treated inserts had increased by 4%;F in comparison to that of the untreated ones% @ine K
carbides impro&e the hardness and wear resistance% Microhardness measurements showed that the hardness
&alues of the treated inserts had increased by /F when compared to those of the untreated inserts%
V ?ryogenic treatment led to an increase of 1F in the grain size of the treated inserts with respect to that of the
untreated ones% >his larger grain size caused to an increase in C? grain contiguity and to increases in the
thermal conducti&ity of the treated inserts%
V At all cutting conditions, the treated inserts showed a better performance than the untreated ones of up to
;F and 4F in terms of flank wear and crater wear, respecti&ely% owe&er, while the treated inserts
e7ibited a notably superior performance of up to /1F compared to the untreated ones in terms of notch wear
at a medium feed rate 3% mm're&5, at a lower feed rate 3%.4 mm're&5, the impro&ement of the treated
inserts in tool performance did not e7ceed /1F%
As a result of wear e7periments and &arious analyses, cryogenic treatment was shown to significantly impro&e
the hardness and wear resistance of the tungsten carbide inserts% >his impro&ement can be e7plained by theincreases in grain size, additional formation of fine K carbide percentage, and high thermal conducti&ity%
Ac-nowledgement
>he authors wish to place their sincere thanks to "azi Pni&ersity +cientific <esearch (ro8ect 6i&ision for
financial support for the (ro8ect No% 0'9.-9%
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