Kesici takımların performansına takım malzemesinin ve tin kaplamanın etkisi
The Effect of tool materials and tin coating on the performance of cutting tools
Yazar: HAYRETTİN AHLATCI
Danışman: DOÇ. DR. HÜSEYİN ÇİMENOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji Mühendisliği Ana Bilim Dalı / Malzeme Bilim Dalı
Derece: Yüksek Lisans, 1997
Konu: Metalurji Mühendisliği = Metallurgical Engineering
Dizin: Kalay = Tin ; Kaplama = Coating ; Kesici takımlar = Cutting tools

Özet:
ÖZET Bu çalışmada Türk Elektrik Endüstrisi Eskişehir tesislerinde ARÇELİK buzdolaplarının GG 25 kalite dökme demirden imal edilen kompresör motor bloklarının talaşlı imalatının yapıldığı takım tezgahlarında farklı özelliklerdeki kesici takımların (matkap, kılavuz ve rayba) kaplamasız ve TiN sert seramik film ile kaplı olarak kullanılması ile kesici takımların ömürlerinde meydana gelen değişimlerin belirlenmesi amaçlanmıştır. Kompresör motor bloklarının talaşlı imalatında kullanılan takımlar, DÎN 1,3343 ve DÎN 1,3243 kalite Yüksek Hız Takım Çeliklerinden imal edilmiştir. DÎN 1,3243 kalite Yüksek Hız Takım Çeliklerinden imal edilen matkaplar, NATO-TU PVD (Fiziksel Buhar Biriktirme) kaplamaları projesi kapsamında Ark PVD yöntemi ileTiN kaplanmıştır. Bu çalışmada DÎN 1,3243 kalite Yüksek Hız Takım Çeliklerinden imal edilen kesici takımlar 400 °C'de 10 dakika, 1000 V bias voltajında ve 8. l O"6 mbar basınçta yapılan sıçratma+ısıtma işleminden sonra 400 °C 'de l saat, 100-400 V bias voltajında ve 1,6.10"" mbar azot kısmi basıncında TiN ile kaplanmışlardır. TiN kaplanmış kesici takımlar üzerinde, kaplama kalınlıklarının, yüzey pürüzlülüklerinin, sertliklerinin ve taban malzemeye olan yapışmalarının belirlenmesi için çeşitli karakterizasyon çalışmaları yapılmıştır. TiN kaplanmış takımlar üzerinde yapılan karakterizasyon çalışmaları sonucunda, kaplama sertliğinin ve kaplama / taban malzeme arayüzeyindeki bağ mukavemetinin kaplama kalınlığına bağımlı olduğu anlaşılmıştır. Kaplamasız ve TiN kaplı kesici takımların takım ömürlerinin belirlenmesi amacıyla yapılan performans deneylerinde kesici takımların serbest yüzeylerinde meydana gelen serbest yüzey aşınması kriter olarak seçilmiştir. Kesici takımların serbest yüzeylerinde meydana gelen serbest yüzey aşınma şerit genişliği 0,4 mm'ye ulaşan takım aşınmış olarak kabul edilmiş ve kesici takımların aşınıncaya kadar işlemiş olduklarıda sayısı veya toplam derinlik (delik sayısı x delik derinliği) takım ömrü olarak alınmıştır. Performans deneyleri sonucunda DÎN 1,3243 kalite Yüksek Hız Takım Çeliklerinden imal edilmiş kesici takımlar, DÎN 1,3343 kesici takımlara göre kesme kuvveti ve hızına bağlı olarak % 15 ile % 495 oranında takım ömürlerinde artış gösterirken TiN ile kaplanmış DÎN 1,3243 takımları ise % 76 ile % 932 oranında takım ömürlerinde artış göstermişlerdir. Kesici takımların GG 25 kalite dökme demirde delik delme işlemleri sırasında sürtünme ile oluşan hasar, kaplamanın kalkması ile başlamakta ve daha sonra açığa çıkan takım malzemesinin aşınması ile devam etmektedir. Takım malzemesinin açığa çıkmış olan bölgelerine yer yer malzeme transferi de olmaktadır. xxıv

Abstract:
1200 800 400 HARDENING 12QQ.C 1. TEMPERING 2. TEMPERING 3. TEMPERING 4. TEMPERING 550 C 550-560 C 540-570 C 540 C 90 minute 90 minute 60 minute 60 minute TIME Fig. 1 In the performance tests heat treatment cycle which applied to cutting tools. Table 3. TiN deposition conditions DIN 1,3243 cutting tools. The characterisation of the uncoated and TiN coated-tools were examined by surface roughness, hardness, coating thickness measurements and scratch tests. Surface roughness at the tools were determined by the stylus profilometer, PEERTHOMETER S8P. Surface roughness values were obtained as the centre line average value, Ra, which is the arithmetic mean value of the vertical deviation of the profile from the centre line. Although the roughness of the twist drills were measured on the flank face, the measurements were carried out on the rake faces of tabs and reamers. XXVI 1Table 1. The geometry of the cutting tools used. Table 2 Contents and Standards of the cutting tools employed. After heat treatments, DIN 1,3243 quality Cutting Tools were coated with TiN by ARC PVD technique. Before coating the tools were heated and cleaned by using titanium ion bombardment with - 1 000 V of a bias voltage under 8.10" mbar of a pressure at 400 ° C for 10 minutes. The conditions of the deposition explored were 50-63 A of arc current, 60 minutes of deposition time, 1,6. 10"2 mbar of nitrogen partial pressure, -100 to -400 V of substrate bias voltage and 400 ° C temperature. Table 3 shows the Arc PVD conditions used in this experiment. XXVI1200 800 400 HARDENING 12QQ.C 1. TEMPERING 2. TEMPERING 3. TEMPERING 4. TEMPERING 550 C 550-560 C 540-570 C 540 C 90 minute 90 minute 60 minute 60 minute TIME Fig. 1 In the performance tests heat treatment cycle which applied to cutting tools. Table 3. TiN deposition conditions DIN 1,3243 cutting tools. The characterisation of the uncoated and TiN coated-tools were examined by surface roughness, hardness, coating thickness measurements and scratch tests. Surface roughness at the tools were determined by the stylus profilometer, PEERTHOMETER S8P. Surface roughness values were obtained as the centre line average value, Ra, which is the arithmetic mean value of the vertical deviation of the profile from the centre line. Although the roughness of the twist drills were measured on the flank face, the measurements were carried out on the rake faces of tabs and reamers. XXVI 1Bulk hardnesses of the uncoated Cutting Tools were measured as Vickers Hardness Number with 10 kg load. The hardness of the TiN coating was accomplished by the FISCHERSCOPE HP 100 XYPROG dynamic ultramicrohardness tester which employed Vickers Indentation Stylus. The load of the microhardness tester were selected as the load which cause indentation depth of 1/10 of the coating thickness. Coating thickness measurements were carried out using the ball crater method by Wirtz Buehler calotest tester. The 10 mm diameter ball rotating at 30 rps (revolutions per second) applied to the coating surface for 20 second. A kerosene diamond suspension was used as the abrasive medium and coating thickness was calculated by a standard formula based on measurement of the crater dimensions and the ball diameter. The coating thickness measurements were performed on the neck of the cutting tools. IPA Scratch Tester was used for the determination of coating adhesion. In this test, a Rockwell C diamond indenter (tip radius 0,2 mm, cone agle 1 20°, loading rate 1 0 N.mm"1, maximum load 130-150 N, scratching speed 10 mm.min." and scratching length 10 mm) was drawn over the surface until the delamination of the coating. The coating surface of the samples were continiously monitored to determine the critical loads and the results were verified by optical microscopy and acustic emission. The results of characterisation tests are given in Table 3. It is found that, the surface roughness of the cutting tools were increased by TiN coating. Although the hardness of DIN 1,3243 quality High Speed Cutting Tools was about 882-920 HV, the ultramicrohardness values of TiN coatings are between 1879 and 2578 HU, depending mainly on the coating thickness. Vickers Hardness Values of the uncoated DIN 1,3343 quality High Speed Cutting Tools were about 700-820 HV. Coating thickness were found in the range 2,3-3,3 p.m. In the Arc PVD processes, the flux of deposition particles moves from the evaporation source towards the substrates. It was therefore not suprising that on the cutting tools the thickness varies on the flank face and rake face since they were facing a different particle flux. One another result is that, the coating thickness on the coated surfaces varies owing to geometrical effects during deposition. The lower (LcO and the upper (LC2) critical loads obtained from scratch tests were utilised for adhesion assessment. Cracking within the coating and the delamination of the coating were used asfailure criteria. As showed in Table 3, the values of Lei for TiN-coated drills change between 16 and 33 N the Lc? values are between 72 and 139 N. It is found that the critical normal force decreased with increasing coating thickness. Table 3. Characteristics of TiN coating. The performance of the uncoated and TiN-coated cutting tools were examined at ESKİŞEHİR Installation of Turkish Electric Industry. The cutting conditions are given in Table 4. % 5 emulsion Bortex Super cutting fluid was used during cutting operation. Table 4. Cutting condition. The performance of the cutting tools during the manufacture of GG 25 quality ( % 3,2-3,5 C, % 2,1-2,4 Si, % 0,6-0,9 Mn, % 0,074 S, % 0,042 P) cast iron compressor motor blocks for ARÇELİK refrigerators were examined with respect to flank wear. The hardness of the compressor motor blocks which were cast by DÖKTAŞ were 1 80-240 HB. The cutting depth of the tools used in each cutting machine is given in Table 5. XXIXTable 5. The cutting depth and the duty of the cutting tools used. Different number of the cutting tools were used at each machining tool in tandem cutting process. The flank wear land width of the cutting tools were measured at regular interval for each machining tool. The maximum value of the flank wear land width of the cutting tool used in each machining tools was recorded. It was assumed that when the flank wear land width reaches to 0,4 mm the cutting tool is worn away and the number of the drilling holes (or maximum drilling distance) until 0,4 mm of the flank wear land witdh, was considered to be the "the tool life". Optic and Scanning Electron Microscopy examination on worn surfaces were carried out to determine the effective wear mechanisms. Scanning electron microscopy examination after ultrasonic cleaning of surfaces was carried out by JSM-5410 Scanning Electron Microscobe. The performance tests of the cutting tools were accomplished by measuring the flank wear land width and the number of the drilling holes. Since the cutting depth of each cutting tool was different, the maximum cutting distance was calculated to prove similar conditions for discussing the test results. The cutting tools were classified into four groups as % 1 1,05 ± % 8 m/min. (for KT 6003 ve KT 6004), 15,15 m/min. (for KT 8037), 26,17 ± % 15 m/min. (for KT 1023, KT 1020, KT 1022 and KT 1003) and 36,47 ± % 11 m/min. (for KT 1057 and KT 1006) with respect to cutting speeds (Table 4). The results XXXof the performance tests were discussed according to (i) tool life (the maximum drilling distance reaching to 0,4 mm of the flank wear land width), (ii) the wear rate (the slope of the flank wear land width vs the maximum drilling distance graphics). Furthermore cutting forces for each cutting tool group were calculated to normalise the cutting parameters such as feed rate and tool geometry which effects tool life. The effect of the maximum drilling distance on the flank wear land width was determined for four different cutting speeds. In Fig. 2, the tool flank wear is plotted against the maximum cutting distance for TiN coated DIN 1,3243 quality High Speed Cutting Tools, uncoated DIN 1,3343 and DIN 1,3243 quality High Speed Cutting Tools for 26,17 ± % 1 5 m/min. of the cutting speed and 27 N of the cutting force. The uncoated DIN 1,3343 suffered severe flank wear in drilling tests and the 0,4 mm flank wear criterion was rapidly reached. The flank wear of TiN coated tools occurs more slowly compared with that of the uncoated DIN 1,3343 and DIN 1,3243, despite the higher cutting force employed. Table 6 shows the tool life which corresponds to the maximum drilling distance in 0,4 mm of the flank wear land width as a function of cutting speeds and cutting forces. 0.60 -| £ 0.50 S X Q H 0.40 0.30 0.20 0.10 T 40000 80000 120000 MAXIMUM DISTANCE (mm) 160000 Fig. 2. In 26. 1 7 ± %1 5 m/min. cutting speed Flank wear land width-maximum drilling distance for KT1023 (O uncoated DIN 1,3343;. uncoated DIN 1,3243; * TiN coated DIN 1,3243). XX\1As seen in Table 6, for 26.17 ± %15 m/min. cutting speed, tool life generally decreases with increasing cutting force and the tool lives of the the uncoated and TiN coated DIN 1,3243 quality High Speed Cutting Steels are higher than DIN 1,3343 quality High Speed Cutting Steels. Although for 26.17 ± %15 m/min. cutting speed and low cutting force, the tool life oLthe uncoated DIN 1,3243 quality High Speed Cutting Steels increase 1,67-fold and that of TiN coated DIN 1,3243 quality High Speed Cutting Steels increase 2, 13 -fold, in higher cutting forces the tool life of the uncoated DIN 1,3243 quality High Speed Cutting Steels increased 2,15-fold and that of TiN coated DIN 1,3243 quality High Speed Cutting Steels increase 4,5-fold with respect to DIN 1,3343 quality High Speed Cutting Steels. Therefore under heavy cutting conditions the use of TiN coated cutting tools was much higher advantage than these of uncoated cutting tools. The general results of the present investigation are summarised below. 1) The tool life and wear resistance of DIN 1,3243 quality high speed tool steels which contain about 5% cobalt in its composition are higher than that of DIN 1,3343 quality cutting tools. The main effect of cobalt in high speed tool steel is to increase the hot hardness. The increase of the cutting efficiency of DIN 1,3243 can be attributed to the high softening resistance of the tools during the cutting operation. The increment observed xxxnin tool life of DIN 1,3243 quality high speed tool steels is about 15 % -495 % with respect to DIN 1,3343 as a function of tool type and cutting parameters ( cutting speeds and cutting forces). 2) DIN 1,3243 quality cutting tools were coated by TiN layer under the following condition. Cleaning and heating Cleaning time: 10 minute Cleaning bias. 1000 volt Cleaning temperature: 400° Cleaning pressure: 8. 10"6 mbar Coating condition Coating time : 1 hours Coating bias : 100-400 volt Coating temperature : 400° Nitrogen partial pressure : 1,6. 10"" mbar The characterisation of TiN coated tools exhibited that: Thickness: 2,3-3,3 u.m Hardness: 1879-3132 HV Roughness: 0,1 1-0,50 m Critical Load: 16-24 N It is concluded that the hardness and the critical load which is the measure of adhesion strength between substrate and coating decrease with increasing thickness. 3) TiN coating of DIN 1,3243 quality high steel tool steels increased the tool lives and wear resistances of cutting tools significantly with respect to uncoated DIN 1,3243 and DIN 1,3343 quality high speed tool steels. TiN coating of DIN 1,3243 quality high steel tool steels increased the tool lives about 76 % - 932 % with respect to DIN 1,3343 quality high speed tool steels as a function of tool type and cutting parameters ( cutting speeds and cutting forces). XXXU14) Microscopic examination on the worn TiN coated cutting tools reveal the failure mechanism in order of coating spallation at many locations and the transfer of the work material to the tool surface where TiN coating was removed. Plastic deformation at tool edges occurs after extensive wear at flank faces. XXXIVBÖLÜM 1 GİRİŞ İnsanlar eski çağlardan bu yana kullandıkları malzemeleri geliştirip amaçlarına daha uygun hale getirmeye çalışmışlardır. Gelişen teknoloji ile beraber insanların kullandıkları malzemelerden beklentileri daha da çeşitlenmiştir. Bu amaçla geliştirilen uygulamaların ekonomikliği de malzemeye kazandırılan özellikler kadar önemlidir. İmalat sanayi, Türkiye'de Gayri Safı Milli hasılat içerisinde katma değeri en büyük olan endüstri sektörüdür. İmalat sanayinin başlıca girdileri arasında kesici takımlar gelmektedir. Kesici takımların performanslarının geliştirilmesi imalat hızının artırılmasını, işlenmiş parçaların yüzey kalitesinin iyileştirilmesini, birim parça başına işleme maliyetinin, kesici takım ve kesici takım stok maliyetinin azalmasını sağlar. Kesici takımların performansını geliştirmede kullanılan başlıca tekniklerden biri malzemelerin yüzey özelliklerini değiştirmektir. Aşınma ve korozyonun zararlı etkileri azaltılarak malzemelerin yüzey özellikleri iyileştirilebilir. Aşınmayı azaltarak takım ömürlerini ve prodüktiviteyi artırmasından dolayı sert kaplamalar, talaşlı üretim proseslerinde bütün ilgiyi üzerlerinde toplamışlardır. Takım performansını artırma amacıyla uygulanan kaplamalardan beklenen özellikler şunlardır: - Yüksek sertlik, - İş parçasına düşük, takım malzemesine yüksek yapışma, - Yüksek aşınma direnci, - Yüksek kimyasal kararlılık ve tokluk, - Düşük çözünürlük, - Yüksek yük taşıma kapasitesi, - Düşük kesme kuvvetleri, - Düşük ısıl yayınma katsayısı.İnce sert nitrür ve karbür kaplamaları bu özelliklere sahip olup, kesici takımlarda başarılı bir şekilde kullanılmaktadır. Günümüzde yaygın olarak kullanılan 4 kaplama vardır: TİN, Tİ(C,N), (Tİ,A1)N ve CrN. Malzeme yüzeylerine ince sert seramik filmlerle kaplanmasında kimyasal ve fiziksel buhar biriktirme (PVD, CVD) teknikleri kullanılmaktadır. Özellikle PVD (fiziksel buhar biriktirme) tekniğinde düşük sıcaklıklarda kaplama yapılabildiğinden daha geniş bir uygulama alanı vardır. Bu çalışmada, bileşiminde kobalt içermeyen ve içeren HSS kalite takım çeliğinden imal edilmiş kesici takımların, kaplamasız ve TİN kaplamalı olarak GG 25 dökme demir iş parçasına karşı göstermiş oldukları performanslarının incelenmesi amaçlanmıştır. Kesici takımlar Ark PVD tekniği ile TİN kaplanmışlardır.