TİN kaplama parametrelerinin aşınma davranışı üzerindeki etkisi
The Effect of coating parameters on the wear behaviour of TİN
- Tez No: 75620
- Danışmanlar: PROF. DR. E. SABRİ KAYALI
- Tez Türü: Yüksek Lisans
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Malzeme Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 223
Özet
ÖZET Malzemeye uygun bir kaplama yapılmasıyla, sürtünme ve aşınma davranışında önemli oranda bir düşüş gözlenir. Fakat bunun için, kaplanmış malzemenin yüzeyi, kaplama, ara yüzey ve taban malzemesinin özellikleri arasındaki ilişkiler iyi bilinmelidir. Kaplanmış bir malzemenin özellikleri, genel olarak bileşim, üretim parametreleri ve mikroyapı tarafından kontrol edilir. Aşınma, altı kısım halinde incelenebilir. Adhezif, abrazif, yorulma, korozif, erozif ve elektrik ark akımlı aşınma olarak sınıflandırılabilen aşınma proseslerinden en sık rastlananı adhezif ve abrazif aşınmadır. Relatif olarak hareket halinde bulunan bir temasın tüm tribolojik prosesi, mekanik sürtünme, aşınma ve deformasyon mekanizmalarını hem mikro düzeyde, hem de makro düzeyde içermesinin yanısıra ayrıca kimyasal etkileri ve malzeme transferini de kapsar. Sert seramik kaplamalar malzeme yüzeylerine, PVD (Fiziksel Buhar Biriktirme) tekniği ile başarılı bir şekilde uygulanabilir. Bu teknikte vakum altında bulunan malzemeler buharlaştırılır veya sıçratılarak atomlar yüzeyden kopartılır. Daha sonra da, kaplama yapılacak yüzey üzerine atomal veya iyonsal olarak biriktirilir. Yaygın bir şekilde kullanılan TİN kaplamaların aşınmasında, kaplamanın yapıldığı proses parametreleri önemli bir etkiye sahiptir. Taban malzemesine uygulanan bias voltajı, taban malzemesinin sıcaklığı, kısmi basınç gibi parametrelerin -kullanılan kaplama prosesi ve kaplama türüne göre optimize edilmesiyle, en düşük sürtünme ve aşınma davranışının elde edilebilmesi mümkündür. Bu çalışmada, HSS malzemesinden üretilmiş numuneler üzerine farklı proses parametrelerinde PVD katodik ark buharlaştırma tekniği ile TİN kaplanmış ve kaplama proses parametrelerinin aşınma davranışı üzerindeki etkisi incelenmiştir. İTÜ Kimya-Metalurji fakültesi kaplama karakterizasyon laboratuarında, kaplanmış numunelerin aşınma deneyleri yapılmış ve numunelerin kaplama kalınlıklarının, yüzey pürüzlülüklerinin, sertliklerinin ve taban malzemeye yapışmalarının belirlenmesi amacıyla karakterizasyon çalışmaları yapılmıştır. Aşınma deneylerinde 5 mm çapında alüminabilya kullanılarak, disk üzerinde bilya deney düzeneğinde TİN kaplanmış numunelerin aşınma davranışı incelenmiştir. Çalışmalar sonucunda, taban malzemesine bias voltajı uygulanmasının aşınma davranışı üzerinde önemli bir etkiye sahip olduğu ve uygulanan bias voltajının artmasıyla aşınma miktarının azaldığı gözlenmiştir. Daha düşük kaplama kalınlığına, daha yüksek sertliğe sahip olan ve taban malzemesine yapışması daha iyi olan kaplamaların, aşınma dirençlerinin daha iyi olduğu bulunmuştur. XVI
Özet (Çeviri)
SUMMARY The Effect of Coating Parameters on the Wear Behaviour of TiN Tribology can be defined as the study of the science and technology of interacting surfaces in relative motion. Tribology can be divided into subjects. These are friction, lubrication and wear. Friction is the resistance to relative motion of contacting bodies. Friction experienced during a sliding condition is known as sliding friction, and friction experienced during a rolling condition is known as rolling friction. Wear is a process of removal of material from one or both of two solid surfaces in solid-state contact. It occurs when solid surfaces are in sliding or rolling motion relative to each other. Lubrication is a process by which the friction and wear between two solid surfaces in relative motion is reduced significantly by interposing a lubricant between them. The classification of wear processes based on the type of wearing contacts, are single phase and multiple phase. In single phase wear, a solid, liquid or gas moving relative to a sliding surface causes material to be removed from the surface. The relative motion may be sliding or rolling. In multiple phase wear, wear also results from a solid, liquid, or gas moving across a surface; but in this case, solid, liquid or gas act as a carrier for a second phase (particle, asperity, liquid drop, and gas bubble) that actually produce the wear. Wear is classified into six categories as follows : 1. Adhesive, galling or scuffing wear 2. Abrasive and cutting wear 3. Fatigue wear 4. Corrosive wear 5. Erosive wear by a) solid particles b) fluid, c) cavitation 6. Electrical arc-induced wear Adhesive wear is often called galling or scuffung. Adhesive wear processes are initiated by the interfacial adhesive junctions that form if solid materials are in contact on an atomic scale. As a normal load is applied, local pressure at the asperities becomes extremely high. Continued sliding causes xviithe junctions to be sheared and new junctions to be formed. The chain of events that leads to the generation of wear particles includes the adhesion and fracture of the mating surfaces. Abrasive wear may be described as damage to a surface by a harder material. It is also someties called scratching, scoring, or gouging depending on the degree of severity. There are two general situations in which this type of wear occurs. In the first case, the hard surface is the harder of two rubbing surfaces (two-body abrasion). In the second case, the hard surface is a third body, generally a small particle of grit or abrasive, caught between the two other surfaces and sufficiently harder than they are to abrade either one or both of them (three-body abrasion). In fatigue wear, repeating stresses in a rolling or sliding contact can give rise to fatigue failure. In practice, all machines involve the periodic variations of stress. In corrosive wear, the dynamic interaction between environment and mating material surfaces plays a significant role. When components are subjected to very small relative vibratory movements at high frequency, an interactive form of wear, called fretting, takes place that is initiated by adhesion, is amplified by corrosion, and hits its main effect by abrasion. Erosion of materials arid components caused by the impingement of solid particles or small drops of liquid or gas can be a life-limiting phenomenon for systems in erosive environments. Cavitation erosion arises when a solid and a fluid are in relative motion and bubbles formed in the fluid become unstable and implode against the surface of the solid. When a high electrical potential is present across a thin air film in a sliding process, a dielectric breakdown results that leads to arcing. This results in considerable melting, corrosion, hardness changes and other phase changes and even in direct ablation of material. The tribological process takes place as the two surfaces are moving in relation to each other, and both physical and chemical changes occur in accordance with physical and chemical laws. As a function of time, the tribological process causes changes in both the geometry and material composition and results in friction, wear, velocity, temperature abd dynamic behaviour. xvuiThe complete tribological process in a contact in elative motion is very complex because it involves simultanously mechanichal friction, wear and deformation mechanisms both at a micro scale and a macro scale as well as chemical effects and material transfer. The macromechanical tribological mechanisms are related to the stress and strain distributions of the whole contact, the total plastic and elastic deformations they result in and the total wear particle formation process and its dynamics. These phenomena are typically of a size level of one micrometre or more, up to a milimetre size. The micromechanical tribological mechanisms are related to stress and strain at an asperity level, crack generation and propagation, material liberation and single particle formation. In typical engineering contacts these are phenomena of a size level of about one micrometre or less, down to a nanometre size. The chemical effects take place on a micro scale and are referred to as tribochemical mechanisms. Material transfer takes place on both a micro and macro level but it is mainly the macro material transfer that influences the friction and wear behaviour. Coating technology has advanced rapidly in the past twenty years and it has greatly assisted in meeting such complex demands placed on materials. Deposition processes can be divied into four categories :. gaseous state processes. solution state processes. molten or semi molten state processes. solid state processes The important coating methods for high technology applications are plasma and detonation gun spraying techniques, electro deposition, chemical vapour deposition (CVD) and physical vapour deposition (PVD). PVD technology consists of the techniques of evaporation, ion plating and sputtering. PVD involves the atomisation or vaporisation of material from a solid source and the deposition of that material on to the substrate to form a coating. Two important characteristic parameters for the coating processes are the thickness of the coatings that can be achieved and the deposition temperature. Titanium nitride (TIN) coating is mainly used on high speed tools for metal cutting but has also found other tribological applications, such as bearings, seals and as an erosion protection layer. One important attraction with titanium nitride is its xixgolden colour which has also encouraged its use in decorative applications. It has excellent tribological properties. Properties of the coatings can be determined by coating characterisation techniques. The main coating characterisation parameters for triboelements are :. Coating thickness. Coating surface roughness. Coating hardness. Coating adhesion to the substrates The adhesion is characterized by means of a newly developed scratch analyzer, equipped with a rockwell C diamond stylus of tip radius D=200 um. In a fully computer controlled experiment, the actual values of the normal load, the frictional force and the acustic emmission are recorded simultaneously. Coating thickness analyses are generally carried out using the ball crater method, where the coating thickness is determined from the dimension of the spherical crater produced on the coating surface. Also, ultra micro hardness testing is used for coating hardness measurements. In this study, the effects of TiN coating parameters on wear behaviour are investigated. The TiN coatings are produced by Arc PVD technique. The wear tests are made with a pin-on-disk wear apparatus, using an alumina pin with a radius of 5 mm. The sample which shows the least coefficient of friction value when a 5 N force applied is sample 1, with coefficient of friction value 0.34. The highest one is sample 3, with coefficient of friction value of 0.55. The sample which shows the least coefficient of friction value when a 7 N force applied is sample 1, with coefficient of friction value 0.34. The highest one is sample 3, with coefficient of friction value of 0.55. The sample which shows the least coefficient of friction value when a 10 N force applied is sample 1, with coefficient of friction value 0.62. The highest one is sample 3, with coefficient of friction value of 0.75. The result of the present investigations are summarized below : 1) Applying a bias voltage has important effects on the properties and wear of the TİN coating. As the applied bias voltage increases, coating thickness decreases. Because, coating becomes more dense. Also the hardness of the coating is increased. 2) As the applied bias voltage increases, the adhesion of the coating to the substrate decreases. The surface roughness decreases too. 3) As the applied bias voltage increases, friction coefficient decreases. Because the number of asperities on the coating decrease too. xx4) As the applied bias voltage increases, the wear scar diameter on the alumina pin decreases. 5) As the applied force used in the wear tests increases, friction and the wear of the coating, and the pin increases too. 6) As the hardness of the coating increases, friction coefficient increases. 7) As the roughness of the coating decreases, the friction coefficient decreases. The optimum process parameters and properties of the TiN coatings in which minimum coefficient of friction values obtained, are as follows :. Bias voltage : - 250 V. Arc current : 80 A. Coating thickness : 2.85 um. Coating hardness : > 30000 N/mm2. Adhesion values : Lci= 46 N, Lc2= 87 N XXI
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