CERAMICS INTERNATIONAL SEVIER Ceramics International 30(2004)2081-2086 www.elseviercom/locate/ceramint Development of Al2O3-SiC composite tool for machining application Young Mok Ko a, Won Tae Kwon,, Young-Wook Kim Received 6 October 2003; received in revised form 13 October 2003; accepted 17 November 2003 Abstract AlyO3-SiC composites containing up to 30 wt of dispersed SiC particles (280 nm)were fabricated via hot-pressing and machined as cutting tools. The Al2O3-SiC particulate composites exhibit higher hardness than their unreinforced matrix because of the inhibited grain growth by adding SiC and the presence of hard secondary phase (SiC). The fracture toughness of the composites remains constant up to 10 wt loading of SiC. For machining heat-treated AISI 4144140 steel, the Al2O3-1O wt SiC composite tool showed the longest tool lif seven times longer than a commercial tool made of Al2O3-TiC composite, while the composite tool with 5 wt SiC showed the longest tool life for machining gray cast iron. The improved performance of the Al2O3-SiC composite tools attributes to the transformation of fracture mode from intergranular fracture for Al2O3 to intragranular fracture for Al2O3-SiC composites C 2004 Elsevier Ltd and Techna S.r.l. All rights reserved Keywords: C Hardness; C Fracture; C. Toughness; D. AlO3; D SiC; E Cutting tools 1. Introduction dition of Sic whisker to Al2O3 matrix improves the fracture toughness and the thermal shock resistance of Al2O3[1, 2, 41 The need for cutting tool materials with improved me- and offers advantages with respect to fracture behavior chanical properties and chemical inertness capable of oper- Al2O3-SiC particulate composites exhibit higher strength ating at high cutting speeds is becoming critical Ceramic and slightly better hardness than their unreinforced matrix, materials are the prime candidates to fulfill these require- whereas the fracture toughness remains practically constant ments because of their excellent physical properties such as [11-13]. The improvement in strength is mainly due to a re thermal stability, high hardness, and good corrosion resis- duction in the size of the surface defects [13, which some- tance. One of most widely used material for the ceramic cut- times may be favored by compressive residual stresses that ting tool is alumina(Al2O3). The addition of hard secondary are induced during machining. If the composite strengthen- phases such as TiC, TiB2, Ti(C, N), ZrO2 particles, and Si ing is mainly a surface phenomenon, it also should modify whiskers to alumina matrix provides great improvement in the wear properties and cutting performance. However, very mechanical properties [1-8]. For example, the additions of few investigations of the wear and cutting performance of TiC and TiB2 particles to Al2O3 matrix improves the frac- Al2O3-SiC composites have been published, and those are ture toughness, the hardness, and the strength over those of focused on the erosive and sliding wear of the composites monolithic Al2O3 and offers advantages to wear and fracture [14, 15]. This paper presents the preliminary results of an behavior when used as cutting tool materials [9, 10). The ad- investigation of the cutting performance of Al2O3-SiC par- ticulate composites in machining a heat-treated AISI 4140 author.Tel:+82-2-2210-2403 steel and a gray cast iron. In this study, we have particularly fax:+82-2-2248-5110. focused on studying the effect of SiC content on tool life of E-mail address: kwon uos ac kr(WT. Kwon) the composite tools 0272-8842/$30.00@ 2004 Elsevier Ltd and Techna S.r. I. All reserved doi:10.1016/ ceramist2003.11.011
Ceramics International 30 (2004) 2081–2086 Development of Al2O3–SiC composite tool for machining application Young Mok Ko a, Won Tae Kwon a,∗, Young-Wook Kimb a Department of Mechanical and Information Engineering, University of Seoul, Seoul 130-743, South Korea b Department of Materials Science and Engineering, University of Seoul, Seoul 130-743, South Korea Received 6 October 2003; received in revised form 13 October 2003; accepted 17 November 2003 Abstract Al2O3–SiC composites containing up to 30 wt.% of dispersed SiC particles (∼280 nm) were fabricated via hot-pressing and machined as cutting tools. The Al2O3–SiC particulate composites exhibit higher hardness than their unreinforced matrix because of the inhibited grain growth by adding SiC and the presence of hard secondary phase (SiC). The fracture toughness of the composites remains constant up to 10 wt.% loading of SiC. For machining heat-treated AISI 4144140 steel, the Al2O3–10 wt.% SiC composite tool showed the longest tool life, seven times longer than a commercial tool made of Al2O3–TiC composite, while the composite tool with 5 wt.% SiC showed the longest tool life for machining gray cast iron. The improved performance of the Al2O3–SiC composite tools attributes to the transformation of fracture mode from intergranular fracture for Al2O3 to intragranular fracture for Al2O3–SiC composites. © 2004 Elsevier Ltd and Techna S.r.l. All rights reserved. Keywords: C. Hardness; C. Fracture; C. Toughness; D. Al2O3; D. SiC; E. Cutting tools 1. Introduction The need for cutting tool materials with improved mechanical properties and chemical inertness capable of operating at high cutting speeds is becoming critical. Ceramic materials are the prime candidates to fulfill these requirements because of their excellent physical properties such as thermal stability, high hardness, and good corrosion resistance. One of most widely used material for the ceramic cutting tool is alumina (Al2O3). The addition of hard secondary phases such as TiC, TiB2, Ti(C,N), ZrO2 particles, and SiC whiskers to alumina matrix provides great improvement in mechanical properties [1–8]. For example, the additions of TiC and TiB2 particles to Al2O3 matrix improves the fracture toughness, the hardness, and the strength over those of monolithic Al2O3 and offers advantages to wear and fracture behavior when used as cutting tool materials [9,10]. The ad- ∗ Corresponding author. Tel.: +82-2-2210-2403; fax: +82-2-2248-5110. E-mail address: kwon@uos.ac.kr (W.T. Kwon). dition of SiC whisker to Al2O3 matrix improves the fracture toughness and the thermal shock resistance of Al2O3 [1,2,4] and offers advantages with respect to fracture behavior. Al2O3–SiC particulate composites exhibit higher strength and slightly better hardness than their unreinforced matrix, whereas the fracture toughness remains practically constant [11–13]. The improvement in strength is mainly due to a reduction in the size of the surface defects [13], which sometimes may be favored by compressive residual stresses that are induced during machining. If the composite strengthening is mainly a surface phenomenon, it also should modify the wear properties and cutting performance. However, very few investigations of the wear and cutting performance of Al2O3–SiC composites have been published, and those are focused on the erosive and sliding wear of the composites [14,15]. This paper presents the preliminary results of an investigation of the cutting performance of Al2O3–SiC particulate composites in machining a heat-treated AISI 4140 steel and a gray cast iron. In this study, we have particularly focused on studying the effect of SiC content on tool life of the composite tools. 0272-8842/$30.00 © 2004 Elsevier Ltd and Techna S.r.l. All rights reserved. doi:10.1016/j.ceramint.2003.11.011
Y M. Ko et al./Ceramics International 30 (2004)2081-2086 Table I Batch composition and sintering condition of ceramic tools Designation Batch composition(wt %) Sintering condition B-Sicb Temperature(°C) Time (h) Pressure(MPa) Atmosphere AOSI AOS4 1700 a.3 um, AKP30, Sumitomo Chemical Co., Osaka, Japan b -280nm, Ultrafine, Ibiden Co., Nagoya, Japan 2. Experimental procedure Chemical composition and mechanical properties of gray cast iron and 2.. Materials AISI 4140 steel used for cutting test Gray cast iron AISI 4140 Commercially available a-Al2O3(0.3 um, AKP30, Chemical composition(wt%/93.0-940 Sumitomo Chemical Co., Osaka, Japan)and B-SIC (280 nm Ultrafine, Ibiden Co., Nagoya, Japan)were used as starting 3.25-3.5 0.380.43 powders. Batch composition and sintering conditions of cr 0.05-0.45 0.8-1.1 each homemade ceramic tool were given in Table 1. AO was 0.15-04 0.5-0.9 fabricated from pure a-Al2O3 for comparison. For investi- 0.05-0.1 gating the effect of Sic addition on mechanical properties 0.05-0.2 and cutting performance of the composites, 5-30 wt. of Max.0.12 Max.0.035 SiC were added to Al2O3. Each batch was ball-milled in Max.0.15 Max.0.04 ethanol for 24 h using Sic balls and a polyethylene jar 1.8-1.3 0.15-0.3 The mixed slurry was dried, subsequently sieved through a Mechanical property 60 mesh screen and hot-pressed at 1550-1700C under HB183-234 HB285-352 RC 20 HRC30-38 pressure of 25 MPa in an argon atmosphere. Sintering time Min. 276 MPa Min 655 MPa was I h for pure Al2O3 and 2 h for the Al2O3-SiC compos- tes Sintered density was measured using the Archimedes method. The sintered specimens were cut and polished up was heat treated again to keep the hardness of the material to I um finish, then etched thermally. The microstructure was observed by inspecting both thermally etched and constant after cutting 3 mm in the depth of cut direction fractured surfaces of the manufactured tool using scanning The cutting tests for machining of heat-treated AISI 4140 electron microscopy (SEM). The hardness was measured were performed at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.25 mm. The tests using a Vickers indenter with a load of 500 g. The fracture for gray cast iron were performed at a cutting speed of toughness was measured by indentation method with a load 330 m/min with a feed rate of 0. 2 mm/rev and a depth of cut of49N[16 of 0.5 mm The dimension of work material was 110 mm in diameter and 350 mm in length. The wear of the tools was 2. 2. Cutting performance determined by measuring the wear depth on the flank face The wear depth was measured by using a tool microscope All experiments were carried out on a computer numer- (Hanra Engineering, Micro Vision System SV-2000, Ulsan, ical control(CNC) lathe(HyundaI HiT-15,Ulsan, Korea) Korea)at more than four points of flank face and the average under dry cutting condition. The sintered composites were of them was taken as a nominal flank wear depth. The tool cut and ground to make SNGN120408(12.7 mm x 12.7 mm, life was considered to be finished when the wear depth on 4.76 mm thickness. 0.8 mm nose radius and 0.2 mm x 200 the flank face reached 0.3 mm. For comparison, three kinds chamfer). A tool holder of CSRNr 2525 M 12CEA type offset shank with 15°[75°] side cutting edge angle,0°in Table 3 ert normal clearance and 25 mm x 25 mm x 150 mm)was Typical composition of commercial tools used for the cutting experiments. The cutting performance Tool material the composite tools was tested by machining heat-treated AISI 4140(HRC: 58)and gray cast iron. Chemical com- AlO3 position and mechanical properties of the AISI 4140 steel C2 Al2O3+ TiC and gray cast iron were given in Table 2. The AISI 4140 Al2O3+ SiC whisker
2082 Y.M. Ko et al. / Ceramics International 30 (2004) 2081–2086 Table 1 Batch composition and sintering condition of ceramic tools Designation Batch composition (wt.%) Sintering condition -Al2O3 a -SiCb Temperature (◦C) Time (h) Pressure (MPa) Atmosphere AO 100a 0 1550 1 AOS1 95b 5 1650 2 AOS2 90b 10 1650 2 25 Ar AOS3 80b 20 1650 2 AOS4 70b 30 1700 2 a ∼0.3m, AKP30, Sumitomo Chemical Co., Osaka, Japan. b ∼280 nm, Ultrafine, Ibiden Co., Nagoya, Japan. 2. Experimental procedure 2.1. Materials Commercially available -Al2O3 (∼0.3m, AKP30, Sumitomo Chemical Co., Osaka, Japan) and -SiC (280 nm, Ultrafine, Ibiden Co., Nagoya, Japan) were used as starting powders. Batch composition and sintering conditions of each homemade ceramic tool were given in Table 1. AO was fabricated from pure -Al2O3 for comparison. For investigating the effect of SiC addition on mechanical properties and cutting performance of the composites, 5–30 wt.% of SiC were added to Al2O3. Each batch was ball-milled in ethanol for 24 h using SiC balls and a polyethylene jar. The mixed slurry was dried, subsequently sieved through a 60 mesh screen and hot-pressed at 1550–1700 ◦C under a pressure of 25 MPa in an argon atmosphere. Sintering time was 1 h for pure Al2O3 and 2 h for the Al2O3–SiC composites. Sintered density was measured using the Archimedes method. The sintered specimens were cut and polished up to 1m finish, then etched thermally. The microstructure was observed by inspecting both thermally etched and fractured surfaces of the manufactured tool using scanning electron microscopy (SEM). The hardness was measured using a Vickers indenter with a load of 500 g. The fracture toughness was measured by indentation method with a load of 49 N [16]. 2.2. Cutting performance All experiments were carried out on a computer numerical control (CNC) lathe (Hyundai HiT-15, Ulsan, Korea) under dry cutting condition. The sintered composites 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 composite tools was tested by machining heat-treated AISI 4140 (HRC: 58) and gray cast iron. Chemical composition and mechanical properties of the AISI 4140 steel and gray cast iron were given in Table 2. The AISI 4140 Table 2 Chemical composition and mechanical properties of gray cast iron and AISI 4140 steel used for cutting test Element Gray cast iron AISI 4140 Chemical composition (wt.%) Fe 93.0–94.0 96.78–97.84 C 3.25–3.5 0.38–0.43 Cr 0.05–0.45 0.8–1.1 Cu 0.15–0.4 – Mn 0.5–0.9 0.7–1.0 Mo 0.05–0.1 0.15–0.25 Ni 0.05–0.2 – P Max. 0.12 Max. 0.035 S Max. 0.15 Max. 0.04 Si 1.8–1.3 0.15–0.3 Mechanical property Hardness HB 183–234 HRC 20 HB 285–352 HRC 30–38 Ultimate tensile strength Min. 276 MPa Min. 655 MPa was heat treated again to keep the hardness of the material constant after cutting 3 mm in the depth of cut direction. The cutting tests for machining of heat-treated AISI 4140 were performed at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.25 mm. The tests for gray cast iron were performed at a cutting speed of 330 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.5 mm. The dimension of work material was 110 mm in diameter and 350 mm in length. The wear of the tools was determined by measuring the wear depth on the flank face. The wear depth was measured by using a tool microscope (Hanra Engineering, Micro Vision System SV-2000, Ulsan, Korea) at more than four points of flank face and the average of them was taken as a nominal flank wear depth. The tool life was considered to be finished when the wear depth on the flank face reached 0.3 mm. For comparison, three kinds Table 3 Typical composition of commercial tools Tool material Typical composition C1 Al2O3 C2 Al2O3 + TiC C3 Al2O3 + SiC whisker
Y.M. Ko et al. /Ceramics International 30(2004)2081-2086 of commercial ceramic tools, made of Al2O3, Al2O3-TiC Table 4 composites, and Al2O3-SiC whisker composites(Table 3), Properties of monolithic AlO3 and Alzo3-SiC composites were selected and tested under the same cutting conditions Designation with the homemade cutting tools (MPan AOS I 3.0±0.3 3.7±0.4 3. Results and discussion AOS3 2.2±0.6 3.4±1.3 4.5±0.3 3..M aerials The sintered densities of the materials are given in Table 4. the composites of Al2O3 and SiC. The facture mode of Ao The density of the materials decreased with increasing Sic was mainly intergranular whereas that of AoSI and AOS2 content because of the theoretical density(3.218 g/cm)of was intragranular. The addition of Sic particles made the C is lower than that(3.987 g/cm)of a-Al2O3 fracture mode changed from intergranular to intragranular Fig. I shows the SEM micrographs of the monolithic fracture. Thermal expansion coefficient mismatch between Al2O3 (designated as AO)and the composites of Al2O3 and Al2O3 and Sic generates large tensile residual stresses in SiC (designated as AOS)after thermal etching at 1500C the matrix grains around intragranular SiC particles [6, 171 for I h in an argon atmosphere. As shown in Fig. 1, the ad- An intergranular crack that encounters an intergranular par- dition of Sic particles inhibited the grain growth of Al2O3 ticle may deflect into the matrix, because of the high inter- and resulted with the smaller grain size. Generally, small facial fracture energy of the Al2O3/SiC interface, promoting Sic particles are distributed throughout the Al2O3 matri- intragranular fract ces, and large Sic particles are located on the boundaries As shown in Table 4. the addition of sic or junctions of Al2O3 grains. Fig. 2 shows the SEM mi- hardness of the composites, but the hardness value of the crographs of the fracture surfaces of monolithic Al2O3 and composites was not dependent on the content of Sic added 25-mn08 GE 25-un-oS s85m03 Fig. 1 SEM micro hermally etched surfaces of monolithic Al2O3 and Al2O3-SiC composites: (a)AO, (b)AOSl, and (c)AoS2(refer to Table 1)
Y.M. Ko et al. / Ceramics International 30 (2004) 2081–2086 2083 of commercial ceramic tools, made of Al2O3, Al2O3–TiC composites, and Al2O3–SiC whisker composites (Table 3), were selected and tested under the same cutting conditions with the homemade cutting tools. 3. Results and discussion 3.1. Materials The sintered densities of the materials are given in Table 4. The density of the materials decreased with increasing SiC content because of the theoretical density (3.218 g/cm3) of -SiC is lower than that (3.987 g/cm3) of -Al2O3. Fig. 1 shows the SEM micrographs of the monolithic Al2O3 (designated as AO) and the composites of Al2O3 and SiC (designated as AOS) after thermal etching at 1500 ◦C for 1 h in an argon atmosphere. As shown in Fig. 1, the addition of SiC particles inhibited the grain growth of Al2O3 and resulted with the smaller grain size. Generally, small SiC particles are distributed throughout the Al2O3 matrices, and large SiC particles are located on the boundaries or junctions of Al2O3 grains. Fig. 2 shows the SEM micrographs of the fracture surfaces of monolithic Al2O3 and Fig. 1. SEM micrographs of thermally etched surfaces of monolithic Al2O3 and Al2O3–SiC composites: (a) AO, (b) AOS1, and (c) AOS2 (refer to Table 1). Table 4 Properties of monolithic Al2O3 and Al2O3–SiC composites Designation Density (g/cm3) Hardness (GPa) Fracture toughness (MPa m1/2) AO 3.96 19.6 ± 2.3 3.8 ± 0.5 AOS1 3.90 22.5 ± 0.8 3.8 ± 0.1 AOS2 3.85 23.0 ± 0.3 3.7 ± 0.4 AOS3 3.71 22.2 ± 0.6 5.2 ± 0.4 AOS4 3.66 23.4 ± 1.3 4.5 ± 0.3 the composites of Al2O3 and SiC. The facture mode of AO was mainly intergranular whereas that of AOS1 and AOS2 was intragranular. The addition of SiC particles made the fracture mode changed from intergranular to intragranular fracture. Thermal expansion coefficient mismatch between Al2O3 and SiC generates large tensile residual stresses in the matrix grains around intragranular SiC particles [6,17]. An intergranular crack that encounters an intergranular particle may deflect into the matrix, because of the high interfacial fracture energy of the Al2O3/SiC interface, promoting intragranular fracture [18]. As shown in Table 4, the addition of SiC increased the hardness of the composites, but the hardness value of the composites was not dependent on the content of SiC added.
Y M. Ko et al./Ceramics International 30 (2004)2081-2086 WD142mm 15.0kv x3 0k 10um ND10.77m 15.0kv x3 0k 10um Fig. 2. Fracture surfaces of monolithic Al2O3 and Al2O3-SiC composites: (a)AO,(b)AoSI, and (c)AOS2(refer to Table 1) The improvement of hardness of Al2O3-Sic particulate rapidly developed right after the interaction of the tool to the composites attributes to both the smaller grain size of the work-material. Microfracture was observed in the material composites and the presence of hard secondary phase(Sic). and seemed to attribute to the rapid development of the flank The toughness remained constant up to 10 wt. loading of wear. Almost similar fast tool wear was observed in com- SiC and increased slightly for 20 and 30 wt. addition (Table 4). The large SiC particles on the grain boundary believed to contribute to the increment of the toughness at high(20 wt %)SiC loadings. The reduced grain size and the transformation of the fracture mode from intergranular to intragranular of the composites may lead to the reduc tion of the fracture toughness whereas crack deflection by Sic particles is expected to contribute the increase in toughness. Thus, these two competing effects seemed to result in the small change of the fracture toughness in the composites. 3. 2. Cutting performance The variation of the flank wear of the homemade and com- mercial tools during machining heat-treated AISI 4140 as a Cutting Time(sec) function of the machining time is shown in Fig. 3. The cut ting tests were performed at a cutting speed of 160 m/min ar of various cutting tools as a function of cutting time during heat-treated AIsI 4140 at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0. 25 mm. with a of 0. 2 mm/rev and a depth of cut of 0. 25 mm(asterisk In the monolithic Al, O3 tool (AO), the flank wear was ()denotes tools broken during machining)
2084 Y.M. Ko et al. / Ceramics International 30 (2004) 2081–2086 Fig. 2. Fracture surfaces of monolithic Al2O3 and Al2O3–SiC composites: (a) AO, (b) AOS1, and (c) AOS2 (refer to Table 1). The improvement of hardness of Al2O3–SiC particulate composites attributes to both the smaller grain size of the composites and the presence of hard secondary phase (SiC). The toughness remained constant up to 10 wt.% loading of SiC and increased slightly for 20 and 30 wt.% additions (Table 4). The large SiC particles on the grain boundary is believed to contribute to the increment of the toughness at high (≥20 wt.%) SiC loadings. The reduced grain size and the transformation of the fracture mode from intergranular to intragranular of the composites may lead to the reduction of the fracture toughness whereas crack deflection by SiC particles is expected to contribute the increase in toughness. Thus, these two competing effects seemed to result in the small change of the fracture toughness in the composites. 3.2. Cutting performance The variation of the flank wear of the homemade and commercial tools during machining heat-treated AISI 4140 as a function of the machining time is shown in Fig. 3. The cutting tests were performed at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.25 mm. In the monolithic Al2O3 tool (AO), the flank wear was rapidly developed right after the interaction of the tool to the work-material. Microfracture was observed in the material and seemed to attribute to the rapid development of the flank wear. Almost similar fast tool wear was observed in com- 0 200 400 600 800 1000 0 200 400 600 * * * * Flank Wear ( mm) Cutting Time (sec) AO AOS1 AOS2 AOS3 AOS4 C1 C2 C3 Fig. 3. Flank wear of various cutting tools as a function of cutting time during machining heat-treated AISI 4140 at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.25 mm (asterisk (∗) denotes tools broken during machining)
8 AO AOS1 AOS2 AOS3 AOS4 C1 AO AOS1 AO Tool materals Tool Materals various cutting tools during machining heat-treated Fig. 6. Tool life of various cutting tools during machining gray cast iron AlsI 4140 at a cutting speed of 160 m/min with a feed rate of 0. 2 mm/rev at a cutting speed of 330 m/min with a feed rate of 0.2 mm/rev and a and a depth of cut of 0.25 mm(asterisk(*)denotes tools broken during depth of cut of 0. 5mm machining) The variation of the flank wear of the homemade and mercially tools(C1-C3). In contrast, the composite tool commercial tools during machining gray cast iron as a func (AOS1-AOS4)have very good wear resistance, as shown in tion of the machining time is shown in Fig. 5. The cutting Fig.3. AOS2 showed the longest tool life among the tools tests were performed at a cutting speed of 330 m/min with sted for machining heat-treated AISI 4140. The tool life a feed rate of 0.2 mm/rev and a depth of cut of 0.5mm of aos2 was seven times longer than that of a commer- The monolithic Al2O3 tool(Ao) was worn out rapidly as cial tool(C2)(see Fig 4). As shown in Fig. 2, the addition it did during machining heat-treated AISI 4140. AOSI with of sic made the transformation of fracture mode from in- tergranular fracture for Al2 O3 to intragranular fracture for tested for machining gray cast iron(Fig. 6). AOS4 showed Al2O3-SiC composites. The improved cutting performance the shortest tool life among the home-made composite tools, but it was still longer than those of commercial tools. The granular fracture mode of the composites. Generally, the tool tool life of AosI was 1.5 times longer than the longest life shortened with increasing the sic content in the com- tool life of selected commercial tool(C1). Generally, the posites. The microfracture was also observed in AOS4 and tool life shortened with increasing the Sic content in the it was considered to be the reason for the shorting of tool composites. This may attribute to the chemical reactions be life in Aos4 tween SiC and Fe in the work-material during machining 4 4. Conclusions The introduction of hard Sic grains into monolithic Al2O3 increased the hardness and decreased the grain size of the material, thereby greatly improving its cutting performance, compared to the commercial tools made of monolithic Al2O3, Al2O3-TiC composites, and Al2O3-SiC whisker composites. The Al2O3-5 wt SiC composites and the Al2O3-l0 wt. SiC composites showed the best cutting performance for machining gray cast iron and heat-treated AISI 4140 steel, respectively. The tool life of the Al2O3-5 wt %SiC and Al2O3-10 wt %SiC composite 0200400 tools was 1.5 times and 7 times longer than those of com- Cutting Time(sec) mercial tools in machining gray cast iron and heat-treated Fig. 5. Flank wear of various cutting tools as a function of cutting tir AISI 4140, respectively. The present results indicate that during machining gray cast iron at a cutting speed of 330 m/min with a the Al2O3-SiC composites are a promising material for feed rate of 0. 2 mm/rev and a depth of cut of 0.5mm machining applications
Y.M. Ko et al. / Ceramics International 30 (2004) 2081–2086 2085 AO AOS1 AOS2 AOS3 AOS4 C1 C2 C3 0 200 400 600 800 * * * Tool Life (sec) Tool Materals Fig. 4. Tool life of various cutting tools during machining heat-treated AISI 4140 at a cutting speed of 160 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.25 mm (asterisk (∗) denotes tools broken during machining). mercially tools (C1–C3). In contrast, the composite tools (AOS1–AOS4) have very good wear resistance, as shown in Fig. 3. AOS2 showed the longest tool life among the tools tested for machining heat-treated AISI 4140. The tool life of AOS2 was seven times longer than that of a commercial tool (C2) (see Fig. 4). As shown in Fig. 2, the addition of SiC made the transformation of fracture mode from intergranular fracture for Al2O3 to intragranular fracture for Al2O3–SiC composites. The improved cutting performance of the Al2O3–SiC composite tools attributed to the intragranular fracture mode of the composites. Generally, the tool life shortened with increasing the SiC content in the composites. The microfracture was also observed in AOS4 and it was considered to be the reason for the shorting of tool life in AOS4. 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0 200 400 Flank wear ( mm) Cutting Time (sec) AO AOS1 AOS2 AOS3 AOS4 C1 C2 C3 Fig. 5. Flank wear of various cutting tools as a function of cutting time during machining gray cast iron at a cutting speed of 330 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.5 mm. AO AOS1 AOS2 AOS3 AOS4 C1 C2 C3 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Tool Life (sec) Tool Materals Fig. 6. Tool life of various cutting tools during machining gray cast iron at a cutting speed of 330 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.5 mm. The variation of the flank wear of the homemade and commercial tools during machining gray cast iron as a function of the machining time is shown in Fig. 5. The cutting tests were performed at a cutting speed of 330 m/min with a feed rate of 0.2 mm/rev and a depth of cut of 0.5 mm. The monolithic Al2O3 tool (AO) was worn out rapidly as it did during machining heat-treated AISI 4140. AOS1 with 5 wt.% SiC showed the longest tool life among the tools tested for machining gray cast iron (Fig. 6). AOS4 showed the shortest tool life among the home-made composite tools, but it was still longer than those of commercial tools. The tool life of AOS1 was 1.5 times longer than the longest tool life of selected commercial tool (C1). Generally, the tool life shortened with increasing the SiC content in the composites. This may attribute to the chemical reactions between SiC and Fe in the work-material during machining [2,4]. 4. Conclusions The introduction of hard SiC grains into monolithic Al2O3 increased the hardness and decreased the grain size of the material, thereby greatly improving its cutting performance, compared to the commercial tools made of monolithic Al2O3, Al2O3–TiC composites, and Al2O3–SiC whisker composites. The Al2O3–5 wt.% SiC composites and the Al2O3–10 wt.% SiC composites showed the best cutting performance for machining gray cast iron and heat-treated AISI 4140 steel, respectively. The tool life of the Al2O3–5 wt.%SiC and Al2O3–10 wt.%SiC composite tools was 1.5 times and 7 times longer than those of commercial tools in machining gray cast iron and heat-treated AISI 4140, respectively. The present results indicate that the Al2O3–SiC composites are a promising material for machining applications
Y M. Ko et al./Ceramics International 30 (2004)2081-2086 Acknowledgements [9D. Jianxin, A. Xing, Wear resistance of Al]O3/iB2 ceramic cutting tools in sliding wear tests and in machining processes, J. Mater. This work was supported by Korean Science and Engi Process.Tech.72(1997)249255 neering Foundation(KOsEF)under Grant No. RO1-2001 [10)Y.W. Kim, J.G. Lee, Pressureless sintering of alumina-titaniu 000-00255-0. carbide composites, J. Am. Ceram. Soc. 72(8)(1989)1333-1337 I1 K. Nihara, New design concept of structural ceramics-ceramic nanocomposites, J Ceram Soc. Jpn. 99(10)(1991)974-982 [12]C E. Borsa, S. Jiao, R.I. Todd, RJ. Brook, Processing and properties References 13] M. Sternitzke, B. Derby, RJ. Brook, Alumina/silicon carbide 1 PF. Becher, G.C. Wei, Toughening behavior in SiC-whiske nanocomposites by hybrid polymer/powder processing: microstruc- einforced alumina, J. Am. Ceram Soc. 67(12)(1984)C267-C269 tures and mechanical properties, J. Am. Ceram Soc. 81(1)(1998) 2] D. Jianxin, A. Xing, Wear behavior and mechanisms of alumina- 41-48 based ceramic tools in machining of ferrous and non-ferrous alloys, [14] M. Sternitzke, E. Dupas, P. Twigg, B. Derby, Surface mechanical Tribol.int.30(11)(1988)807-813 properties of alumina matrix nanocomposites, Acta Mater. 45(10) [3]ED. Whitney, P.N. Vaidyanathan, Microstructural engineering of (1997)3963-3973 ic cutting tools, Ceram. Bull. 67(6)(1988)1010-1014 [15]J. Rodriguez, A. Martin, J.Y. Pastor, J. Llorca, J.F. Bartolome, J.S. (4]SF. Wayne, S.T. Buljan, The role of thermal shock on tool life of Moya, Sliding wear of alumina/silicon carbide nanocomposites, J elected ceramic cutting tool material, J. Am. Ceram. Soc. 72 (5) Am. Ceram.Soc.82(8)(1999)2252-2254 1989)754-760 [16] G.R. Anstis, P. Chantikul, B R. Lawn, D B. Marshall, A critical eval- 5]T. Sornakumar, Advanced ceramic-ceramic composite tool materials uation of indentation techniques for measuring fracture toughness: I for metal cutting application, Key Eng. Mater. 114(1996)173-188. Direct crack measurements, J. Am. Ceram Soc. 64(1981)533-534 6] M. Stermitzke, Review: structural ceramic nanocomposites, J.Eur [17]I Levin, W.D. Kaplan, D.G. Brabdon, A.A. Layyous, Effect of Sic 知为(m购 Cera.Soc.17(1998)1061-1082 [7A. Krell, P. Blank, L M. Berger, V. Richter, Alumina tools for machining chilled cast iron, hardened steel, Am. Ceram. Soc. Bull 78(12)(1999)65-73. .L. Jenkins, A quantitative analysis of crack-interface inter- ction in alumina-based nanocomposites, Philos. Mag. A 78(1998) 07-522
2086 Y.M. Ko et al. / Ceramics International 30 (2004) 2081–2086 Acknowledgements This work was supported by Korean Science and Engineering Foundation (KOSEF) under Grant No. R01-2001- 000-00255-0. References [1] P.F. Becher, G.C. Wei, Toughening behavior in SiC-whiskerreinforced alumina, J. Am. Ceram. Soc. 67 (12) (1984) C267–C269. [2] D. Jianxin, A. Xing, Wear behavior and mechanisms of aluminabased ceramic tools in machining of ferrous and non-ferrous alloys, Tribol. Int. 30 (11) (1988) 807–813. [3] E.D. Whitney, P.N. Vaidyanathan, Microstructural engineering of ceramic cutting tools, Ceram. Bull. 67 (6) (1988) 1010–1014. [4] S.F. Wayne, S.T. Buljan, The role of thermal shock on tool life of selected ceramic cutting tool material, J. Am. Ceram. Soc. 72 (5) (1989) 754–760. [5] T. Sornakumar, Advanced ceramic–ceramic composite tool materials for metal cutting application, Key Eng. Mater. 114 (1996) 173–188. [6] M. Sternitzke, Review: structural ceramic nanocomposites, J. Eur. Ceram. Soc. 17 (1998) 1061–1082. [7] A. Krell, P. Blank, L.M. Berger, V. Richter, Alumina tools for machining chilled cast iron, hardened steel, Am. Ceram. Soc. Bull. 78 (12) (1999) 65–73. [8] B. Kerkwijk, J.J.C. Buizert, H. Verweij, Tribological tests verify wear resistance, Am. Ceram. Soc. Bull. 79 (1) (2000) 49–53. [9] D. Jianxin, A. Xing, Wear resistance of Al2O3/TiB2 ceramic cutting tools in sliding wear tests and in machining processes, J. Mater. Process. Tech. 72 (1997) 249–255. [10] Y.-W. Kim, J.G. Lee, Pressureless sintering of alumina–titanium carbide composites, J. Am. Ceram. Soc. 72 (8) (1989) 1333–1337. [11] K. Niihara, New design concept of structural ceramics-ceramic nanocomposites, J. Ceram. Soc. Jpn. 99 (10) (1991) 974–982. [12] C.E. Borsa, S. Jiao, R.I. Todd, R.J. Brook, Processing and properties of Al2O3/SiC nanocomposites, J. Microsc. 177 (3) (1995) 305– 312. [13] M. Sternitzke, B. Derby, R.J. Brook, Alumina/silicon carbide nanocomposites by hybrid polymer/powder processing: microstructures and mechanical properties, J. Am. Ceram. Soc. 81 (1) (1998) 41–48. [14] M. Sternitzke, E. Dupas, P. Twigg, B. Derby, Surface mechanical properties of alumina matrix nanocomposites, Acta Mater. 45 (10) (1997) 3963–3973. [15] J. Rodriguez, A. Martin, J.Y. Pastor, J. Llorca, J.F. Bartolome, J.S. Moya, Sliding wear of alumina/silicon carbide nanocomposites, J. Am. Ceram. Soc. 82 (8) (1999) 2252–2254. [16] G.R. Anstis, P. Chantikul, B.R. Lawn, D.B. Marshall, A critical evaluation of indentation techniques for measuring fracture toughness: I. Direct crack measurements, J. Am. Ceram. Soc. 64 (1981) 533–538. [17] I. Levin, W.D. Kaplan, D.G. Brabdon, A.A. Layyous, Effect of SiC submicrometer particle size and content on fracture toughness of alumina–SiC nanocomposites, J. Am. Ceram. Soc. 78 (1) (1995) 254–256. [18] S. Jiao, M.L. Jenkins, A quantitative analysis of crack–interface interaction in alumina-based nanocomposites, Philos. Mag. A 78 (1998) 507–522
