WO2012091535A1

WO2012091535A1 - Zirconia-toughened-alumina ceramic inserts with the addition of nano particle metal oxides as additives

Info

Publication number: WO2012091535A1
Application number: PCT/MY2010/000330
Authority: WO
Inventors: Arifin Ahmad ZAINAL; Maran Ratnam MANI; Mohamad HASMALIZA; Zahirani Ahmad Azhar AHMAD
Original assignee: Universiti Sains Malaysia
Priority date: 2010-12-27
Filing date: 2010-12-27
Publication date: 2012-07-05
Also published as: MY158139A

Abstract

The present invention provides cutting insert for cutting machinery comprising a Zirconia Toughened Alumina (ZTA) having a nano metal oxide additive. A method method of fabricating cutting insert is also provided. The method comprises mixing alumina together with Yttria Stabilized Zirconia (YSZ) and nano metal oxide additives; compacting the mixture in a compaction mold of a desired shape; sintering the compacted mixture for a predetermined period; and machining the sintered mixture to form the cutting insert.

Description

Zirconia-toughened-alumina Ceramic Cutting Inserts With The Addition of Nano Particle Metal Oxides As Additives

Field of the Invention

[0001] The present invention relates to ceramic cutting inserts. In particular, the present invention relates to ceramic cutting inserts having Zirconia-Toughened- Alumina (ZTA) and method of fabricating the same.

Background

[0002] Ceramic tools have a high resistant to heat and wear. It can be used as a cutting tool for machineries, especially as a tool to cut metal that are extremely hard. Such cutting tools are often used in lathe machineries, whereby it is a machine tool that spins a workpiece. The cutting tool, better known as a cutting insert in the lathe machineries, functions as a tool that removes material from the workpiece. The capability of the machine and the finishing of the workpiece rely strongly on the performance of the cutting insert. Cutting inserts with superior mechanical properties operates longer and are capable of cutting harder materials.

[0003] Zirconia Toughened Alumina (ZTA) is a type of ceramic composite consisting primarily Aluminum Oxide (AI2O3), commonly known as alumina and Yttria stabilized zirconia (YSZ or Y^Os-ZrOa),. ZTA has an improved hardness and toughness making it a suitable material for cutting inserts, as hardness and toughness are imperative in the cutting inserts application. [0004] The making of ceramic materials and manufacturing of the product goes through a series of processes that may vary due to the type of application needed. One basic process required in producing ceramic composites is the sintering process.

[0005] Sintering is a method used for making objects from powder. It is generally used to manufacture ceramic products. The materials are heated in a sintering furnace below its melting point till all the particles adhere together. The main purpose of sintering is to increase the strength of the material by bonding the particles together. Sintering of ceramic materials reduces the pores that occur when the particles are bonded together. One such sintering additive is the Magnesium Oxide (MgO), as it greatly affects the ceramic material by addition in a very small amount MgO reduces the sintering temperature and grain size of alumina. The addition of small amounts of the MgO together with alumina allows the alumina to sinter to near theoretical density. Sintering is an important step in the manufacturing of ceramic tools as high density and low porosity cutting insert are the requirements for a wear-resistant application. [0006] Currently, the manufacturing of ceramic cutting inserts with ZTA is proven to be superior in its resistance and wear. This is with the aid of alumina or MgO additions. However, as the world continues to progress and advance in our manufacturing industry, it is important to have machineries that are able to keep up with the increasing needs. Although ZTA cutting inserts have been proven to offer improved hardness and toughness, it should not be limited to continual improvements in its properties. Summary

[0007] In one aspect of the present invention, there is provided a cutting insert for cutting machinery comprising a Zirconia Toughened Alumina (ZTA) having a nano metal oxide additive. [0008] In one embodiment, the ZTA comprises of 99.99 wt% - 97.0 wt% and

0.01 wt% - 3.0wt% of nano metal oxide additive. The additive may also be nano-sized Magnesium Oxide.

[0009] In another embodiment, the ZTA comprises a mixture of 80 wt % of alumina and 20 wt % of Yttria Stabilized Zirconia. [0010] Desirably, the cutting insert may be shaped into a square shape, an orthogonal shape, a triangle shape or a semi-orthogonal shape.

[0011] In another aspect of the present invention, there is provided a method of fabricating cutting insert. The method comprises mixing alumina together with Yttria Stabilized Zirconia (YSZ) and nano metal oxide additives; compacting the mixture in a compaction mold of a desired shape; sintering the compacted mixture for a predetermined period; and machining the sintered mixture to form the cutting insert.

[0012] In one embodiment, the alumina is mixed with YSZ in ethanol for round eight hours. The method may further comprises drying up ethanol. Preferably, the sintering process is taken place under about 1600 degree Celsius for around four hours. Brief Description of the Drawings

[0013] This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

[0014] FIG. 1 is a flow chart of the method to fabricate ZTA-nano metal oxides ceramic cutting inserts;

[0015] FIG. 2 is a graph that shows a sintering profile for the ZTA-nano metal oxides ceramic cutting inserts;

[0016] FIG. 3 illustrates the various types of shapes available to fabricate the

ZTA-nano metal oxides ceramic cutting insert;

[0017] FIG. 4 shows the parameters and values of a cutting condition of a test taking place as illustrated in FIG. 5;

[0018] FIG. 5 is a graph of the test that compares the flank wear limit of the present invention and its prior art;

[0019] FIG. 6 illustrates the dimensions of the ZTA-nano metal oxides ceramic cutting insert; and

[0020] FIG. 7 shows the various mechanical properties and values of the newly fabricated ZTA-nano metal oxides ceramic cutting insert. Detailed Description

[0021] The following descriptions of a number of specific and alternative embodiments are provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details. Some of the details may not be described in length so as to not obscure the invention. For ease of reference, common reference numerals will be used throughout the figures when referring to same or similar features common to the figures.

[0022] FIG. 1 shows a process 100 for fabricating a ZTA-nano metal oxides ceramic cutting insert 150 in accordance with an embodiment of the present invention. The fabrication of the ZTA-nano metal oxides ceramic cutting insert 150 includes mixing compositions at step 102; compacting the mixture at step 104; sintering the particles at step 106, and fabricating the sintered material to at step 108. The process 100 is carried out to form the cutting insert 150 comprises aluminum oxide (also referred to as "Alumina") 152, Yttria Stabilized Zirconia (YSZ or Y₂0₃-Zr0₂) 154 and nano metal oxides 156. Briefly, at the step 102, the alumina 152, YSZ 154 and nano metal oxides 156 are mixed at a desired amount. Subsequently, at step 104, the mixture is being pressed into a desired shape of the cutting insert 150 through a compaction mold (not shown). At step 106, the compacted mixture is undergone the sintering process. MgO, for example, can be used as an additive, but others additives may also be desired. The selection of additives is well known in the art, and is therefore not discussed herewith. [0023] Still referring to FIG. 1, the alumina 152 is the main material involved in the fabrication of the ZTA-nano metal oxides ceramic cutting insert 150. It has a chemical formula of AI2O3 and has excellent electrical properties along with high hardness and wear resistant. YSZ 154 is a zirconium oxide based ceramic with an addition of yttrium oxide. It has a chemical formula of Y₂C>3-Zr0₂ and is added to the alumina 152 as reinforcement. YSZ 154 also has properties that demonstrate hardness. When the YSZ 154 is mixed with alumina 152, the material offers improved mechanical properties, namely hardness and toughness, as compared to a pure YSZ cutting insert or a pure alumina cutting insert. For example, the ZTA may consists of 80 wt % of AI2O3 and 20 wt % of YSZ. The weight percentage of the ZTA in the ZTA- nano metal oxides ceramic cutting insert is desired to be in the range of 97.0 wt% - 99.99 wt%. The weight percentage of the nano metal oxides in the ZTA-nano metal oxides ceramic cutting insert 150 is in the range of 0.01wt% - 3.0wt%. The nano metal oxide 156 is used as an additive in the present invention to further improve the properties of the cutting insert 150.

[0024] Still referring to FIG. 1 wherein the process 100 is illustrated in a greater detail. The process 100 aims to fabricate the ZTA-nano metal oxides ceramic cutting insert 150 that comprise the alumina 152, the YSZ 154 and the nano metal oxides 156. At the step 102, the alumina 152, the YSZ 154 and the nano metal oxides 156 are wet mixed in ethanol for a period of around eight (8) hours. This ensures that the mixture is homogenous, i.e. the substance will be uniform in composition even when its volume has been divided. Subsequently, the mixture is dried up in an oven at around 80°C to remove the ethanol. At the step 104, the mixture goes through the compaction process, whereby it is pressed into a desire shape of the cutting insert 150 with an aid of a compaction mould and a hydraulic hand press. FIG. 3(a)-(d) exemplifies various desired shapes of the cutting insert 150. The pressure used in the compaction process is around 200MPa to form the desired shape. At the step 106, the compacted mixture is sintered in an electric furnace at about 1600°C for a period of around four (4) hours. At the step 108, the sintered mixture is under through the machining process to form the ZTA-nano metal oxides ceramic cutting insert 150.

[0025] The sintering process 106 is catered for decreasing the pores between the various materials. The additions of the nano metal oxides 156 further fills up the porous found in ZTA composites resulting a far superior type of ceramic cutting insert 150.

[0026] FIG. 2 is a graph that shows a sintering profile 200 of the sintering process at step 106 of FIG. 1 for fabricating the ZTA-nano metal oxides ceramic cutting inserts 150 in accordance with one embodiment of the present invention. As mentioned, the sintering process is carried out on the compacted mixture in an electric furnace. The electric furnace first increases the heat at a rate 5°C/minute until the temperature reaches about 1600°C. Then the compacted mixture is being soaked under 1600°C for about 4 hours. Thereafter, the electric furnace is being cooled down at a 5°C/minute to complete the sintering process.

[0027] FIGs. 3(a)-(d) illustrate the various embodiments of the fabricated ZTA-nano metal oxides ceramic cutting insert 150 of the present invention. The respective shapes of the ZTA-nano metal oxides ceramic cutting inserts 150 includes: (a) an orthogonal shaped cutting insert, (b) a square shaped cutting insert, (c) a triangle shaped cutting insert and (d) a semi-orthogonal shaped cutting insert. The exemplified cutting inserts are suitable for carrying out cutting operation for a lathe machine for example.

[0028] FIG. 4 shows table listing out various parameters and values of a cutting test with one of the aforesaid ZTA-nano metal oxides ceramic cutting insert cutting inserts 150 and cutting inserts that made by pure Alumina and conventional ZTA respectively. The cutting test aims to determine the performance of these material by measure their Flank wear (V_b, mm) in time. In this cutting test, the cutting speed is being set at 540RPM, the cutting depth is being set at 0.4mm, the feed rate is being set at 0.2mm/rev, the cutting length is being set at 40mm to cut a stainless steel 316L grade workpiece without any lubricant used. The cutting depth is the depth that the cutting insert is in contact with the workpiece. The feed rate is established to produce the surface finish required on the workpiece. The cutting test determines which material used would reach a Flank wear limit, which is set at around 0.3mm.

[0029] As shown in the FIG. 5, the ZTA-nano metal oxides ceramic cutting insert 150 out performed the pure alumina and conventional ZTA, where the pure alumina and the conventional ZTA took around one (1) minutes and around two (2) minutes respectively to reach the Flank wear limit, whilst the ZTA-nano metal oxides ceramic cutting insert 150 took around 4 minutes before reaching the Flank wear limit.

[0030] The flank wear limit denotes a maximum value determined for failure under the cutting test. Flank wear occurs when a portion of the cutting insert that is in contact with the workpiece wears down. Flank wear is the most desired form of tool wear, in which tool wear describes the gradual failure of the cutting insert 000 due to conventional applications. [0031] FIG. 6 is a table listed out dimensions of the ZTA-nano metal oxides ceramic cutting inserts 150 in accordance with one embodiment of the present invention. The ZTA-nano metal oxide ceramic cutting insert 150 is fabricated into a size with a length of 18.0mm, a width of 15.5mm, a thickness of 8.0 and a weight of 4.0g. It is important to recognize that the dimensions of a cutting insert is determined based on the required specification of a particular machine and the type of cutting required.

[0032] FIG. 7 shows various mechanical properties and values of the fabricated

ZTA-nano metal oxides ceramic cutting insert 150 illustrated in FIG. 6. The cutting insert 150 in this embodiment has a hardness of 1740 kg/mm², a fracture toughness of 4-8 MPa.m^{1 2}, an elastic modulus of 310GPa, a density of 4.1 g/cm³ and the maximum operating temperature of 1500°C.

[0033] The above description illustrates various embodiments of the present invention along with examples of how aspects of the present invention may be implemented. While specific embodiments have been described and illustrated it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the present invention. The above examples, embodiments, instructions semantics, and drawings should not be deemed to be the only embodiments, and are presented to illustrate the flexibility and advantages of the present invention as defined by the following claims:

Claims

A cutting insert for cutting machinery comprising a Zirconia Toughened Alumina (ZTA) having a nano metal oxide additive.

The cutting insert according to claim 1 , wherein the ZTA comprises of 99.99 wt% - 97.0 wt% and 0.01wt% - 3.0wt% of nano metal oxide additive.

The cutting insert according to claim 1, wherein the additive is nano-sized Magnesium Oxide.

The cutting insert according to claim 1 , wherein the ZTA comprises a mixture of 80 wt % of alumina and 20 wt % of Yttria Stabilized Zirconia.

The cutting insert according to claim 1, wherein the cutting insert is shaped into a square shaped.

The cutting insert according to claim 1 , wherein the cutting insert is shaped into an orthogonal shape.

The cutting insert according to claim 1 , wherein the cutting insert is shaped into a triangle shape.

The cutting insert according to claim 1 , wherein the cutting insert is shaped into a semi-orthogonal shape.

A method of fabricating cutting insert, the method comprising: mixing alumina together with Yttria Stabilized Zirconia (YSZ) and nano metal oxide additives; compacting the mixture in a compaction mold of a desired shape; sintering the compacted mixture for a predetermined period; and machining the sintered mixture to form the cutting insert.

10. The method of claim 9, wherein the alumina is mixed with YSZ in ethanol for round eight hours.

11. The method of claim 10, further comprising drying up ethanol.

12. The method of claim 9, wherein the sintering process is taken place under about 1600 degree Celsius.

13. The method of claim 12, wherein the sintering process is taken place for around four hours.