Study on the development of ceramic cutting tool (ZTA I ZTA-MGO) and its machining performance in slot milling
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Date
2010
Authors
Hassan, Mohd Nor Hakim
Journal Title
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Abstract
From the various cutting insert materials available, ceramic materials have
the potential to be used as cutting insert due to the attractive properties such as high
hot hardness, abrasion resistance and chemical stability but the base material suffers
from the limitation of low fracture toughness and low thermal shock resistance
capability. Yttria stabilized zirconia (YSZ) and magnesia (MgO) were introduced
into the alumina (ceramic material) in order to toughen the brittle ceramics. Previous
studies found that an addition of 0.7 wt % of MgO into the Zirconia Toughened
Alumina (ZTA) matrix (80 wt % alumina + 20 wt % YSZ) as an insert in lathe
machining, produced minimum wear area. However, the potential of these cutting
insert compositions were not carefully investigated in lathe or milling operation.
Therefore, this research investigated the potential of these inserts from ZT A material,
ZT A reinforced with MgO and commercial available cutting insert in slot milling
operation and three objectives were indentified. Firstly, to design and fabricate die
used for pressing ceramic powder. Secondly, to investigate the performance of these
inserts and thirdly, to compare the performance of these inserts with chosen
Kennametal ceramic insert at the same slot milling operation. The die was designed
using Catia V5R17 software and fabricated using SKD 11 tool steel. Raw materials
consist of alumina, YSZ and magnesia were mixed with desired composition for
eight continuous hours in mixing bottle. Hydraulic pressed were carry out using
fabricated die to obtain the green body insert. These green bodies were sintered in
pressureless condition at 1600 °C for four hours soaking time. The samples were
subjec1ed to analysis such as Vickers hardness, fracture toughness and
microstructural observation. Slot mill operation was implemented to access insert
cutting tools performance. Milling operation was carefully designed to access the
performance of fabricated ceramic cutting inserts with various cutting speeds, feed
rates, axial depth of cut and radial depth of cut. The performance showed by ZTAMgO
insert at cutting speed of 84 and Ill m/min was slightly better than showed by
ZTA insert. ZTA-MgO was able to mill the \vorkpiece with longer time than ZTA ·
insert. The best performance obtained with ZTA-MgO insert at a cutting speed of
111 m/min and a feed rate of 0.20 mm/tooth which able to machine as many as 105
seconds of cutting time under the maximum flank wear of 0.3 mm. While the best
performance obtained with ZT A insert at a cutting speed of 84 wJmin and a feed rate
of 0.20 mm/tooth which able to machine up to 115 seconds of cutting time at the
maximum flank w>;:a:r of 0.3 mm. However, the results clearly indicated at all feed
rates and cutting speeds, the performance of Kennametal inserts outperformed the
performance showed by the other inserts. The best cutting performance acquired with
Kennametal insert was at a cutting of 84 m/min and a feed rate of 0.20 mmltooth
which able to machine the workpice as many as 3 750 seconds of cutting time at the
maximum flank wear value of 0.3 mm. Considerably good surface roughness values
were obtained with all of unworn inserts. The results obtained with the ZTA and
ZTA-MgO inserts were comparable to Kennametal inserts