CERAMICS CUTTING TOOLS: DEVELOPMENT AND APPLICATION ON
GRAY CAST IRON
J.V.C. Souza1, C. Santos, 2, M. V.Ribeiro3, O.M.M. Silva4, M. C. A.Nono1
1
INPE - Av. dos Astronautas, 1.758, S. J. Campo s - SP, CEP. 12245-970, Brazil
2
FAENQUIL-DEMAR – Polo Urbo Industrial, Gleba AI-6, s/n, Lorena - SP, CEP. 12600-000, Brazil
FEG-UNESP – Av.Ariberto Ferreira da Cunha, 333, Guaratinguetá – SP, CEP. 12516-410, Brazil
3
4
CTA-IAE/AMR - Pça. Marechal do Ar Eduardo Gomes, 50, S. J. Campo s - SP, CEP. 12228-904, Brazil
vitor@las.inpe.br
Abstract
Machining is a major manufacturing process and plays a key role in the creation of
wealth. Important is development of new ceramic cutting tools that have unique chemical
and mechanical properties as these tools can offer an increase in metal removal rates,
extending tool life and having the ability to machine hard materials too. When properly
applied these tools can provide the manufacturing engineer with a means of reducing
machining costs and increasing productivity. Presently the Si3N4 ceramic cutting tool
inserts are developed using additives powders that are pressed and sintered in the form of a
cutting tool insert at a temperature of 1850oC. Physical and mechanical properties are
evaluated and subsequent machining studies are conducted on a grey cast iron workpiece to
evaluate the performance of the ceramic cutting tool.
Keywords: Si3N4; Ceramics; New cutting tool; Flank wear; Roughness.
* Corresponding author. Tel.: +55 (12) 3945-6679, 39456989, FAX: +55 (12) 3945-6717
E-mail address: vitor@las.inpe.br (J.V.C. Souza)
1. Introduction
The need for improving the technological performance of machining operations as
assessed by tool-life time, forces and surface finish, has long been recognized to increase
the economic performance of the machining operation [1]. Continual improvement in the
technological performance of machining operations have been sought through research and
development, including new and more wear-resistant tool materials as well as new
geometrical tool designs [2]. One of the most important developments in the past decades
has been the advance in ceramic tool materials that are being increasingly used in
machining operations [3]. While ceramic tool materials can significantly increase tool-life
time and hence reduce production times and costs, the extremely low fracture toughness
associated with these materials has limited their applications [4].
Advances in ceramic composites have resulted in the emergence of newer materials
[5]. Control of microstructures has led to the development of ceramic composite cutting
tool materials like titanium-carbide-added alumina, zirconia-toughened alumina and
silicon-carbide whisker-reinforced alumina which are successfully used for cutting tool
applications [6 and 7]. Apart from binary ceramic–ceramic composites, it is possible to
develop advanced ternary ceramic–ceramic composites for cutting tool applications using
the combination of different ceramic materials [8]. Aluminum, yttrium, cerium oxide have
exceptionally good properties like high hardness, chemical inertness, high melting point
and wear resistance [9, 10, 11 and 12].
Recently Si3N4-coated ceramic cutting tools have been used and claimed to improve
significantly the tool-life time, enabling components to be machined at higher “economic”
speeds, and to reduce the forces and power involved due to the lower frictional coefficients
on the rake face [13].
The present work attempts to investigate the possibility of a new development of
ceramic cutting tools with Si3N4-based ceramic, from which the tool inserts are made to
maintain the effectiveness and improvement in the cutting performance. Two different
Si3N4-based compositions were prepared, named SNYA1 and SNYA2. These were
fabricated through the N2 pressing technology in order to obtain different compositions.
After a characterization of the new ceramic-tool materials, tests of the cutting performance
of the new ceramic were presented.
2. Heat generation in machining
In the metal-cutting process the tool carries out the cutting action by overcoming the
shear strength of the workpiece material. This generates a large amount of heat in the
workpiece resulting in a highly localized thermo mechanically-coupled deformation in the
shear zone. High temperatures in the cutting zone considerably affect the stress–strain
relationship, fracture and the flow of the workpiece material. Generally, increasing
temperature decreases the strength of the workpiece material and thus increases its
ductility. It is now assumed that nearly all of the work done by the tool and the energy input
during the machining process are converted into heat. The heat is generated in three main
regions during the cutting process, as follows: a) Heat is generated in the primary
deformation zone due to plastic work done on the shear plane. The local heating in this
zone results in very high temperatures, thus softening the material and allowing greater
deformation. b) Heat is generated in the secondary deformation zone due to work done by
deforming the chip and in overcoming the sliding friction at the tool/chip interface zone. c)
Heat is generated in the tertiary deformation zone, at the tool/workpiece interface, is due to
the work done to overcome friction, which occurs at the rubbing contact between the tool
flank face and the newly machined surface of the workpiece.
Heat generation and
temperatures in the primary and secondary zones depend highly on the cutting conditions
while heat generation in the tertiary zone is strongly influenced by the tool flank wear. In
summary, the power consumption and the heat generation in metal-cutting processes
dependent on a combination of the physical and chemical properties of the workpiece
material, cutting-tool materials and cutting conditions and the cutting tool´s geometry [14].
3. Gray cast iron properties
The composition of grey cast iron is subject to quantitative changes in its components;
even so, the mechanical properties of the workpiece obtained should be stable [15] so that
the subsequent machining process does not develop any problems. A usual practice in the
cast iron manufacturing process is to leave the choice of chemical composition in the hands
of the foundryman, who will choose the one which adapts best to the needs of the client
without forgetting, of course, that the requirements of his own foundry installations are
determinant in order to obtain the desired properties [16 and 17]. Gray cast iron is an
important material for the automotive industry and its microstructure usually consists of
flake graphite and a matrix of pearlite and/or ferrite, which gives its mechanical properties,
machining performance, and soon, and these depend mainly on its microstructure [18].
Gray cast iron has a pearlite matrix and its chemical composition and mechanical properties
are given in Table 1.
4. Wear behavior
The main wear mechanisms in ceramic cutting tools are abrasion, adhesion, diffusion,
plastic deformation and fracture. The cutting tools are subjected to high localized stresses,
high temperatures, sliding of the chip along the tool is rake face and sliding of the
machined surface along the tool´s flank. These conditions induce tool wear, which in turn
adversely affects tool life time, the quality of the machined surface and its dimensional
accuracy
5. Experimental procedure
Two different Si3N4-based compositions were prepared using the following high
purity starting powders: SNYA1, 85.0 α-Si3N4– 5.0 Y2O3–10.0 AlN (H. C. Starck) and
SNYA2, 80.0 α-Si3N4–8.0 Y2O3–12.0 AlN (H. C. Starck) in wt. % to obtain different
ceramics cutting tools. The starting powders were weighed and milled in water-free
isopropyl for 8 hrs. in an agate jar using agate milling media. The mixed powders were
dried and subsequently sieved. The green bodies were fabricated by uniaxial pressing under
a 50 MPa pressure and subsequent isostatic pressing under a 300 MPa pressure. After
compaction, samples showed dimensions of 15.86 x 15.86 x 6.5 mm and green density of
60 % by geometric methods. Before sintering, the samples were involved in 70 % Si3N4 +
30 % BN as powder bed, and then introduced in a furnace with a graphite heating element
(Thermal Technology Inc. type 1000-4560-FP20) in a nitrogen atmosphere. The heating
rate employed was 25 oC/min. up to a maximum sintering temperature of 1850 oC with a
holding time of 2 hours. The cooling rate was the same as the heating rate. The density of
the samples was measured by the Archimedes method and the weight loss was determined
before and after sintering measurements. The surfaces of the sintered samples were
removed (at least 2 mm) and then the phase composition was analyzed by the X-ray
diffraction technique using Cu-K radiation and scanning speed equal to 0.02 deg/s.
Microstructural characterization was performed with a scanning electron microscope
(SEM). The samples for SEM examination were smoothed and polished samples were
submitted to chemical etching in a NaOH : KOH mixture (1:1 at 500 oC/10 minutes) to
reveal the microstructure.
The hardness was determined by Vicker´s indentations under an applied load of 20N
for 30 s. For statistical reasons, 20 indentations were made to each sample. The fracture
toughness was determined by the measurement of crack length created by indentations. The
calculation of the fracture´s toughness values was done through a relation proposed by
Evans et al., valid for Palmqvist-type cracks, conform to equation (1) [20 and 21].
KIC = 0.16(E/H)1/2.F.b-3/2
(1)
Where: KIC = fracture toughness [MPa.m1/2]; E = Young modulus of material [GPa];
HV = Vickers hardness [GPa]; b = crack size [m] and F = applied load [N].
6. Cutting performance
All experiments were carried out on a computer numerically controlled (CNC) lathe
(Romi, Mod. Centur 30D) under dry cutting condition. The sintered Si3N4 cutting tools
were cut and ground to make SNGN120408 (12.7 mm×12.7 mm, 4.76 mm thickness,
0.8 mm nose radius and 0.2 mm×20° chamfer). A tool holder of CSRNR 2525 M 12CEA
type (offset shank with 15° [75°] side cutting-edge angle, 0° insert normal clearance and 25
mm×25 mm×150 mm) was used for the cutting experiments. The cutting performance of
the new cutting tools was tested by machining gray cast iron, using a composition giving
the best mechanical properties.
The cutting tests for machining gray cast iron were performed at cutting speeds of
150, 230, 400 m/min with a feed rate of 0.30 mm/rev and a depth of cut of 1.0, 2.0, 3.0 mm.
The dimension of the work material was about 105 mm in diameter and 300 mm in length.
The wear of the tools was determined by measuring the wear depth on the flank face by
using a scanning electron microscopy (LEO-1450 VP) at more than four points of the flank
face and the average of them was taken as a nominal flank wear depth. Flank wear of 0.3
mm (ISO 3685) and the abrupt variation of Ra and Ry were used as the end tool-life
criterion. However, to measure the temperature, an infrared pyrometer was used which
measures the tool/chip temperature without physical contact. The workpiece surface
roughness was measured by a micrometer (Mitutoyo Surftest 402 series 178).
7. Results and discussion
7.1. Sintering
The particle size distributions of both powder batches, SNYA1 and SNYA2, showed
that the average particle size found was approximately 0.48 – 0.62 μm, resulting in very
similar green densities of both green samples. The SNYA2 sample had 98.75 ± 0.16 %
relative density slightly higher than SNYA1 sample which had 97.92 ± 0.22 % relative
density. The mass losses during the sintering were about 2 % in both samples. This
behavior demonstrates the viability of using Y2O3/AlN as sintering additives, promoting
similar sintering activity for both sample´s compositions, as expected because of the same
additives with only slightly different amounts. Thus the sintering parameters applied are
adequate to produce ceramics cutting-tools at high density.
7.2. X-ray difractometry (XRD)
The sintered SNYA1 sample show β-Si3N4 present as the main matrix phase Fig.1.
The randomly distributed grains of Si3N4 ceramic fabricated through N2-pressure sintering
lead to isotropic mechanical and physical properties [22]. The phase of Y2Si3O3N4 was
identified from the XRD spectra and the formation of this phase can be explained by the
following reaction equation.
Y2O3+Si3N4→Y2Si3O3N4
(2)
The X-ray diffraction pattern of a sample designated as SNYA2 (N2-pressure
sintering at 1850 °C) is shown in Fig. 2. As seen in Fig. 2, a majoritary α-SiAlON phase
was identified suggesting the existence of a sintering-complete system. Fig. 2 shows the
relationship between the phase formation and the amount of additive which will reflect in
an increase of mechanical properties whilst the Y2Si3O3N4 phase disappears. A higher
sintering temperature of 1850oC and a 20 % amount of additive was an effective procedure
to improve the mechanical properties and reduce the intergranular phase. Therefore, in this
work samples with 15 and 20 % Y2O3/AlN as sintering additives were densified
completely. This is coincident with the results presented by Santos et al.[9].
7.3. Microstructure and mechanical properties
As shown in Fig. 3, the microstructure of SNYA1 consists of elongated β-Si3N4
grains randomly distributed in a matrix. The elongated β-Si3N4 grains are well developed
and have an irregular cross-section perpendicular to the growth direction. The β-Si3N4
grains have an average grain size of about 4.5 μm and aspects ratios higher than 5.1 μm.
This demonstrates the efficiency of the gas-pressure sintering process [23 and 24]. The
intergranular phase located between the grains was revealed and created during the etchingoff of the grain-boundary phase.
In order to examine the effect of the amount of additives on the microstructure and
morphology of Si3N4 ceramic cutting tool, the micrograph of a sample of (SNYA2) sintered
at temperatures of 1850°C is illustrated in Fig 4. At lower amount of additive, most of the
α-SiAlON grains are equiaxed and small, Fig. 3 and confirm what is seen in Fig. 1. As the
amount of additive increases, the volume fraction and the average quantity of α-SiAlON
grains also increases. In a previous report, the formation of the elongated α-SiAlON grains
was explained by means of the reduction of the driving force for the nucleation [9]. These
studies show that the formation of elongated grains is directly related to the sintering
parameters, time, temperature and isothermal holding time, as well as to the characteristics
of the starting powders [25].
In Fig.4, one can appreciate the change in the average grain size of about 3.8 μm and
aspect ratios higher than 4.2 μm, thus confirming the formation of α-SiAlON with an
elongated microstructure.
In this paper it is possible to evaluate the effect of material density on hardness. The
SNYA1 and SNYA2 compositions show the variation of hardness with density. As
expected, the hardness of SNYA2 increases with increasing relative density and the highest
value for hardness (21.52 GPa) is achieved in the sample with the highest relative density,
i.e., 98.75 %. Similar results for the variation of hardness with density were observed in the
SNYA1 sample, which presented a decrease with the decrease of relative density and of the
value of hardness (18.90 GPa).
It is interesting to note that the growth of elongated β-Si3N4 grains did occur in the
SNYA1 composition investigated, suggesting that the self-reinforcement for this
composition is operational and may lead to an enhancement in toughness. In addition to
composition, it was found that the amount of additive has an equally important role in
promoting the growth of the elongated grains and volume fraction. The SNYA2
composition showed the change of the average grain aspect ratio and grain volume fraction
of 15 % additive, sintered at temperatures of 1850°C, the same as for the amount of
additive of 20 %: for both the grain aspect ratio decreased and the volume fraction of the
grains increased.
The effect of grain aspect ratio and elongated grain volume fraction is observed on
fracture toughness for samples sintered with different amounts of additive. The results
showed clearly that there is a relationship between fracture toughness and both the grain
aspect ratio and volume fraction of the elongated grains. Unlike for the aspect ratio and
volume fraction of the elongated grains, no definite relationship exists between fracture
toughness and grain diameter (grain width). However the SNYA1 sample has shown a
fracture toughness of 5.92 MPa m1/2 and the SNYA2 sample a fracture toughness of
5.45 MPa m1/2. Fig. 3 and Fig. 4 shows the measured change of fracture toughness as a
function of average grain diameter (grain width). The high fracture toughness caused by a
high degree of crack deflection is consistent with the large grains and high aspect ratios.
Despite the clear difference in grain morphology and toughness values, the SNYA2
sample has a high hardness of over 21 GPa. This is because the high hardness of α-SiAlON
ceramics is an intrinsic property and is derived from the crystal structure. The longer
atomic stacking sequence (ABCD) in α-SiAlON increases the slip resistance of the
dislocations, offering a higher hardness compared to β-Si3N4 or β-SiAlON, which have a
relatively lower hardness (15–16 GPa) due to the shorter atomic stacking sequence (AB).
7.4. Machining performance of α-SiAlON new cutting tool
The effect of various types of tool wear on tool life time at different cutting speeds is
analyzed. The tool wear affects tool life time, quality of the machine is surface, its
dimensional accuracy and consequently the economics of the cutting operations [26, 2]. In
this paper we discuss some types of tools wear at different cutting speeds. During the test
one can observe the decisive advantage of high cutting speeds. This is made possible by the
layer of graphite coating the surface of the tool, giving an extremely low value of the
friction coefficient leading to better stability between the cutting tool and the workpiece. It
is known that one of the major ways to improve tool life time and wear behavior during
cutting is to reduce cutting forces. In the machining of gray cast iron, the low friction
coefficient values start at elevated temperatures, they do not affect the microstructure of the
α-SiAlON cutting tool due to the dissolution of the graphite phase which is uniformly
distributed throughout the matrix, as can be seen in Fig. 5 (micrographic), providing
improvements in the service characteristics and resulting in prolonged tool life time. During
the cutting process the chip slides against the tool rake face at high speed, inducing a high
cutting temperature and showing high wear resistance of the α-SiAlON cutting tool. Under
such high cutting temperature conditions, the graphite solid lubricant may be released and
smeared, presenting high performance machining. Just as was conclude by Sliney, H.E.
(1982), graphite is a high-temperature lubricant due to its low shear strength, therefore
when there is a lubricant film on the wear surface the matrix endures the load and friction
occurs on the lubricant film [27]. However the friction coefficient value drops, decreasing
the cutting forces and stabilizing heat generation at the tool/workpiece interface which
ultimately results in an overall wear intensity reduction. This is an example of friction
control with a positive feedback of machining conditions. In synergy with the others
coolants, which are used during some machining process in the formation of the lubricant
layer, this leads to a significant increase in tool life time. Combining this data with that of
the tool life time, we can conclude that the lubricant/protective graphite film that is formed
on the tool surface during cutting predominantly isolates the workpiece from the cutting
tool surface. That is why dry machining of the gray cast iron becomes quite efficient if it is
applied at a higher cutting speed. It is possible that the layer-structured coated tool surface
enhances the main beneficial phenomena, a mass transfer at the start of the running-in stage
that results in the quick generation of a tribo-layer with suitable composition and
microstructure. It seems that these self-adaptive, synergistically-alloyed features are
preparing the α-SiAlON ceramic tool for severe applications associated with hightemperature. According to Fig. 6 and 7 (Surface roughness) the cutting speed was found to
have an obvious effect on the friction coefficient at the tool/chip interface. It is indicated
that the friction coefficient show a downward trend with an increase of the cutting speed for
the α-SiAlON ceramic tool due to the presence of graphite as a solid lubricant. The cutting
tool used for applications on gray cast iron should be based on the understanding of the
synergistic action during the friction of alloying elements that are present in the workpiece.
However the direction of research that deals with the complexity of friction, including in-
depth understanding of the self-organization process and the improvement of performance
in machining process, might be a trend for future dry machining.
7.5. Wear behaviour
The fracture of Fig 8 and Fig 9 is related to low speed and cutting depth, which
permit a variety of thermal events of thermomechanical and themochemical nature. These
events take place during turning, resulting in the long run in the transfer of many microconstituents on the contacting surfaces. During low speed operation a high slope of the
wear rate versus machining time indicates a marginal influence of the cutting speed on the
wear rate in dry conditions due to a severe cracking tendency, a situation that resulted in the
loss of proper contact of the cutting tool with the workpiece material. In Fig. 10 (Vb x Lc)
one can observe that during the turning of the gray cast iron at low speeds the stability of
the α-SiAlON ceramic cutting tool is not favoured. This fact can be related to the cutting
temperature which is relatively low when cutting at low speed (as seen in Fig. 11). In these
conditions the graphite material may not be softened and released at low-speed cutting
conditions. Thus, the reduction in friction coefficient at the tool/chip interface is not notable
at low cutting speed. Therefore, lower cutting speeds provide minor adhering capability to
the lubricant particles on the sliding surfaces required for smearing and lubricating film
formation is slowed, causing increasing wear rate and possible vibrations that could be
attributed to the increased severity of evident surface damage. The opposite facts were
observed in Fig. 12 (v=400 m/min, ap=2.0 mm) and Fig 13 (v=400, ap=3.0 mm) and
confirmed in Fig. 10 (Vb x Lc), where the cutting speed increases and the cutting
temperature increases monotonically, as seen in Fig. 11 (temperature). Under high cutting
temperatures, the graphite material may be softened, released and smeared on the tool rake
and flank face, and results in a decrease in the friction coefficient due to more effective film
formation. Reduction in the wear rate in presence of high cutting speeds, suppressing the
cracking tendency of the cutting tool, therefore provides better opportunities for the
lubricating phase (graphite flakes) present within the workpiece to smear and form a stable
lubricant film along the machining process. However as seen in Fig. 8, Fig. 9 and Fig. 13, it
is possible to observe the formation of dark patches on the rake face surface of the αSiAlON ceramic cutting tool. The tribo-induced layer formed in such cases also becomes
stable and contributes more effectively to improve wear performance. Consequently, it is a
further improvement in the wear performance, causing the wear rate to be a minimum
noticed in the graphite-lubricating environment. In accordance with the test above, graphite
lubricants at high speeds provide longer times and suppress the cracking tendency. In Fig.
12 and Fig. 13 no chipping is shown whilst fracture and only a slight flank wear is
observed, presenting abrasive wear as the dominant mechanism. In Fig. 12 we show the
development of grooves and ridges in the direction of the tool sliding against a newly
machined surface of the work piece, the high severity of this situation is seen then in Fig.
13. The abrasive wear is due to crack development and intersection caused by wear
particles acting as small indenters on the tool face. Therefore, the same cutting speed
(v=400 m/min) measured on the flank surface, VB, as a function of total machined time
exhibits similar behavior for both cutting speeds which might indicate that there were no
wear transitions and the wear mechanism is the same throughout the cutting process, as
seen in Fig. 10. In agreement with other papers the results presented in this work using αSiAlON new cutting tools are unique for machining gray cast iron in these conditions.
7.6. Surface finish
Similar behavior was observed during the machining tests, which showed a change
in average surface roughness using α-SiAlON ceramic tools in different cutting conditions.
The Ra and Ry values record only a short increase at the beginning of the cut (first 1,44 min
parts to Vc=150 m/min), then start to decrease evenly below the initial value recorded with
a new tool. Fig. 6 and Fig. 7 present a change of the average surface roughness for wear
trials in different conditions. The analysis of a micrometer (Mitutoyo Surftest 402 series
178) used in the wear trials revealed a difference in slope versus the machined time, and
this is explained by the fact that during machining time there is a layer of graphite coating
the surface of the tool that gives an extremely low value of the friction coefficient. When
higher cutting speeds were used, the wear did not grow so fast and steeply as for the
Vc=150 m/min test. This phenomenon is attributed to the temperature of the chips, which
was higher for higher speeds leading to the softening of the chip-edge sawing action. The
four types of cutting conditions displayed different effects on the workpiece relative to the
surface roughness. It was noted that Ra and Ry decrease almost constantly with the increase
of machining time with a tendency to reach the plateau stage towards the end of the tool
life, mainly due to higher cutting speeds. In a special case an irregular behavior was
observed in the Vc=150 m/min. In Fig. 6 and Fig. 7 irregular changes of the roughness in
machining time 14.33 min are presented. It was noted that the tool broke on the rake face,
proving the increases of the values of Ra and Ry and due to the possible adhesion of microparticles of the α-SiAlON ceramic tool, which have different roles to play during the sliding
movement. It is possible that after the breakage of the tool the cutting edge is still fresh, the
topography of the machined surface is close to the less appropriate geometrical shape of the
turning process. In a second stage, after few minutes of cutting, a rapid decrease of Ra and
Ry was recorded. This decrease is explained through the new accommodation of the flank
face and rake face. Therefore the irregularities of the cutting edge lead to a not even
distribution of peaks and valleys over the surface profile. Moreover, this behavior was
confirmed by the replicated test at Vc= 400 m/min; ap=2.00 mm and Vc= 400 m/min;
ap=3.00 mm which presented lower surface roughness.
8. Conclusion
A new ceramic cutting tool insert has been developed in our laboratory and its
machining performance on grey cast iron workpiece has been rather promising:
1- The α-SiAlON ceramic tool presented a decisive advantage at high cutting speeds
with a reduction in the wear rate in the presence of high cutting speeds in view of the
suppressed cracking tendency of the cutting tool due to the layer of graphite coating the
surface of the tool and giving an extremely low value of the friction coefficient, leading to a
better stability between the cutting tool and the workpiece.
2- The performance of the α-SiAlON ceramic tool used for machining gray cast iron
should be based on the understanding of the synergistic action during friction of alloying
elements that are present in the workpiece.
3- When machining at low speed a high slope of the wear rate was observed,
indicating severe cracking tendency, situation that resulted into a loss of proper contact of
the cutting tool with the workpiece material, resulting in the irregular behavior of Ra and Ry
due to the breakage of the tool on the rake face which made possible the adhesion of micro
particles at the tool/workpiece interface.
4- The results reached were attributed to properties of the α-SiAlON ceramic cutting
tool insert and to the machining conditions.
Acknowledgement
The authors would like to thank CAPES and FAPESP for their financial support.
References
[1] W. Grzesik and T. Wanat, Surface finish generated in hard turning of quenched alloy
steel parts using conventional and wiper ceramic inserts, International Journal of Machine
Tools and Manufacture, 46, (2006), PP. 1988-1995.
[2] T. Sornakumar, Advanced ceramic–ceramic composite tool materials for metal cutting
applications, Key Eng Mater 114 (1996), pp. 173–188.
[3] S.K. Bhattacharyya, E.O. Ezugwu and A. Jawaid, The performance of ceramic tool
materials for the machining cast iron, Wear 135 (1989), pp. 147–159.
[4] A. Senthil Kumar, A. Rajadurai and T. Sornakumar, Development of alumina–ceria
ceramic composite cutting tool, Int J Refract Metals Hard Mater 22 (2004), pp. 17–20.
[5] Mitomo, M. and Petzow, G., (Guest Editors), Recent progress in silicon nitride and
silicon carbide ceramics. MRS Bull., 1995, 2, 19-41.
[6] T. Sornakumar, M.V. Gopalakrishnan, R. Krishnamurthy and C.V. Gokularathnam,
Development of alumina and Ce-TTZ ceramic–ceramic composite (ZTA) cutting tool, Int J
Refract Metals Hard Mater 13 (1995) (6), pp. 375–378
[7] I.-W. Chen and A. Rosenflanz, A tough SiAlON ceramics based on α-Si3N4 with a
wisker-like microstructure. Nature 389 16 (1997), pp. 701–704.
[8]T. Sornakumar, R. Krishnamurthy and C.V. Gokularathnam, Machining performance of
phase transformation toughened alumina and partially stabilized zirconia composite cutting
tools. J. Eur. Ceram. Soc. 12 6 (1993), pp. 455–460.
[9] C. Santos, K. Strecker, S. Ribeiro, J.V.C. Souza, O.M.M. Silva and C.R.M. Silva,
Mater. Lett. 58 (2004), pp. 1794–1796.
[10] An Kyongjun, S. Kakkaveri Ravichandran, Rollie E. Dutton and S.L. Semiatin,
Microstructure, texture, and thermal conductivity of single-layer and multilayer thermal
barrier coatings of Y2O3-stabilized ZrO2 and Al2O3 made by physical vapour deposition, J
Am Ceram Soc 82 (1999) (2), pp. 399–406.
[11] Hongzhi Wang, Lian Gao, Zhijian Shen and Mats Nygren, Mechanical properties and
microstructures of Al2O3–5 vol.% YAG composites, J Eur Ceram Soc 21 (2001) (6), pp.
779–783.
[12] Daniel Casellas, Adrian Feder, Luis Llanes and Marc Anglada, Fracture toughness and
mechanical strength of Y-TZP/PSZ ceramics, Scripta Mater 45 (2001), pp. 213–220.
[13] T.T. Sudo et al., O Desgaste de Ferramentas na Usinagem de Fofo Cinzento a Alta
Velocidade, O Mundo da Usinagem. Sandvik Coromant do Brasil (first ed.) (2001).
[14] Y. Takeuchi, M. Sakamoto and T. Sata, Improvement in the working accuracy of an
NC lathe by compensating for thermal expansion, Precision Eng. 4 (1982) (1), pp. 19–24.
[15] Metals Handbook: Melting and Casting of Ferrous Metals, American Society for
Metals, 8th ed., vol. 5, 1970.
[16] S. Kantz, Trends in melting plant practice in the USA, in: BCIRA International
Conference on Progress in melting cast irons, Warmick, 1990.
[17] I. Minkotf, The Physical Metallurgy of Cast Iron, John Wiley & Sons, London, 1983.
[18] H.T. Angus, Cast Iron: Physical and Engineering Properties (2nd ed.), Butterworths
(1976).
[19] A. G. Evans, E. A. Charles, J. Ceram. Soc. 1976, 59 pp 7- 8.
[20] S.Y. Luo, Y.S. Liao and Y.Y. Tsai, Wear characteristics in turning high hardness alloy
steel by ceramic and CBN tools, J Mater Process Technol 88 (1999), pp. 114–121.
[21] Sunil Dutta, Fracture toughness and reliability in high-temperature structural ceramics
and composites: prospects and challenges for the 21st Century, Bull Mater Sci 24 (2001)
(2), pp. 117–120.
[22] Y.K. Jeong and K. Niihara, Microstructure and mechanical properties of pressureless
sintered Al2O3/SiC nanocomposites, Nano-struct Mater 9 (1997) (1–8), pp. 193–196.
[23] H. Mandal, New developments in α-SiAlON ceramics. J. Eur. Ceram. Soc. 19 (1999),
pp. 2349–2357.
[24] Z.J. Shen, L-O. Nordberg, M. Nygren and T. Ekström, α-SiAlON grains with high
aspect ratio — Utopia or Reality. In: G.N. Babini, M. Haviar and P. Sajgalik, Editors,
Engineering Ceramics‘96; Higher Reliability Trough Processing, Kluwer Academic, The
Netherland (1997), pp. 169–177.
[25] G. Woetting, B. Kanka and G. Ziegler, Microstructural characterization, and relation to
mechanical properties of dense silicon nitride. In: S. Hampshire, Editor, Non-Oxide
Technical and Engineering Ceramics, Elsevier, London (1986), pp. 83–96.
[26] C.W. Beeghly. In: J.A. SwartleyLoush, Editor, Tool Materials for High Speed
Machining, ASM International, USA (1987), p. 91.
[27] H.E. Sliney, Solid lubrication materials for high temperatures-a review, Tribology
International 15 (1982), pp. 303–314.
List of captions for illustrations
Fig. 1. X-ray diffraction patterns of SNYA1.
Fig. 2. X-ray diffraction patterns of SNYA2.
Fig. 3. SEM micrograph of the sintered SNYA1 sample.
Fig. 4. SEM micrograph of the sintered SNYA2 sample.
Fig. 5. TEM micrograph of grey cast iron.
Fig. 6. Surface roughness (Ra) vs. machining time (t).
Fig. 7. Surface roughness (Ry) vs. machining time (t).
Fig .8. SEM micrographs of the wear profile to cutting speed v=150 m/min, depth of cut
ap=1.0 mm, feed rates f=0.30 mm/r, cutting time t=17 min).
Fig .9. SEM micrographs of the wear profile to cutting speed v=230 m/min, depth of cut
ap=2.0 mm, feed rates f=0.30 mm/r, cutting time t=10 min).
Fig. 10. Flank wear (Vb vs machining time (t).
Fig. 11. Temperature (T) vs. machining time (t).
Fig .12. SEM micrographs of the wear profile to cutting speed v=400 m/min, depth of cut
ap=2.0 mm, feed rates f=0.30 mm/r, cutting time t=13 min.
Fig .13. SEM micrographs of the wear profile to cutting speed v=400 m/min, depth of cut
ap=3.0 mm, feed rates f=0.30 mm/r, cutting time t=17 min.
Table 1. Chemical composition and mechanical properties of gray cast iron.