Study on the development of ceramic cutting tool (ZTA I ZTA-MGO) and its machining performance in slot milling

Loading...
Thumbnail Image
Date
2010
Authors
Hassan, Mohd Nor Hakim
Journal Title
Journal ISSN
Volume Title
Publisher
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
Description
Keywords
Citation