Recrystallization and oxidation behavior of commercial purity titanium
Recrystallization and oxidation behavior of commercial purity titanium
Dosyalar
Tarih
2004
Yazarlar
Güçlü, Mehmet
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Institute of Science and Technology
Özet
Titanyum ve alaşımları biomedikal uygulamalarda mükemmel özelliklerinden dolayı kullanılmaktadır. Ancak zayıf tribolojik performansları, servis koşullarında uzun dönem kullanımlarını sınırlamaktadır. Tİ-6A1-4V alaşımından üretilen implantlarda oluşan aşınma ürünleri çevredeki dokuyla zararlı reaksiyonlara girmektedir. Ticari saflıkta titanium üstün korozyon direnci nedeniyle dişçilik uygulamaları için mükemmel bir malzemedir. Titanyumun zayıf aşınma özellikleri yüzey mühendisliği yoluyla arttırılabilir. Yüzey sertleştirme mekanizmalarından biri oksit tabakası ve onun altında oksijen difüzyon zonu oluşturan termal oksidasyondur. Termal oksidasyon korozyon ve aşınma dayanımını artırması gibi avantajları olsa da soğuk işlemle sertleştirilmiş malzemelerde kütlesel sertliğin kaybına sebep olur. Bu çalışmada, ticari saflıkta titanyumun soğuk haddeleme ile deformasyon sertleşmesi ve termal oksidasyon ile yüzey sertleşmesi davranışı incelenmiştir. Ticari saflıkta titanyumun oda sıcaklığında haddelemesiyle yoluyla sertleşmesi HV=284.6 E0108 bağıntısı ile ifade edilebilir. Ancak, soğuk deformasyona uğramış titanyumun termal oksidasy onu esnasında yeniden kristalleşmeye bağb olarak kütlesel sertliği düşmektedir. Yeniden kristalleşme çalışmaları, Grade 2 CP titanyumun yeniden kristalleşme aktivasyon enerjisinin 57 ve 83 kJ/mol aralığında olduğunu göstermiştir. Termal oksidasyon sonucunda yüzeyde oksit tabakası ve onun altında oksijen difüzyon zonu oluşumu ile birlikte incelenen Grade 2 titanyumun yüzey sertliği artmıştır. Termal olarak oksitlenmiş numuneler üzerinde yapılan kinetik çalışmaları titanyumda, termal oksidasyon öncesinde uygulanan soğuk haddelemeye bağlı olarak oksit tabakası kalınlaşması ve oksijen difüzyon aktivasyon enerjisinin sırası ile 75-225 ve 122-204 kJ/mol olduğunu ortaya çıkarmıştır.
Titanium and its alloys are employed in biomedical applications due to their excellent properties; however poor tribological performance limits their long term use in the service conditions. Tİ-6AI-4V alloy, which is used for orthopedic implants, suffers much from wear. Wear of implants causes eventual adverse tissue reactions by producing wear debris resulting with the loosing of the implant. Commercial purity Grade 2 titanium is a suitable material for dental applications, fixation screws and bone plates which exhibits excellent corrosion resistance. Poor wear properties of titanium and its alloys can be improved by means of surface engineering. Thermal oxidation is one of the surface hardening method which consists of the formation of oxide layer and oxygen diffusion zone beneath it. Thermal oxidation of cold worked titanium and its alloys results in loss of bulk hardness. In the present study, bulk hardening by cold rolling and surface hardening by thermal oxidation behaviors of commercial purity titanium were examined. Hardening of commercial purity titanium during room temperature rolling can be expressed as HV = 284.6 e0108. However, during thermal oxidation cold worked titanium significantly lost its bulk hardness due to recrystalization. Recrystalization studies revealed that recrystallization activation energy of Grade 2 CP titanium is in between 57 and 83 kJ/moI. Thermal oxidation resulted in formation of oxide layer with an oxygen diffusion zone beneath and leaded surface hardening. Kinetic studies conducted on thermally oxidized samples resulted in calculation of the activation energies for oxide layer thickening and oxygen diffusion in titanium as 75-225 and 122-204 kJ/mol, respectively, depending on the amount of cold work prior to thermal oxidation.
Titanium and its alloys are employed in biomedical applications due to their excellent properties; however poor tribological performance limits their long term use in the service conditions. Tİ-6AI-4V alloy, which is used for orthopedic implants, suffers much from wear. Wear of implants causes eventual adverse tissue reactions by producing wear debris resulting with the loosing of the implant. Commercial purity Grade 2 titanium is a suitable material for dental applications, fixation screws and bone plates which exhibits excellent corrosion resistance. Poor wear properties of titanium and its alloys can be improved by means of surface engineering. Thermal oxidation is one of the surface hardening method which consists of the formation of oxide layer and oxygen diffusion zone beneath it. Thermal oxidation of cold worked titanium and its alloys results in loss of bulk hardness. In the present study, bulk hardening by cold rolling and surface hardening by thermal oxidation behaviors of commercial purity titanium were examined. Hardening of commercial purity titanium during room temperature rolling can be expressed as HV = 284.6 e0108. However, during thermal oxidation cold worked titanium significantly lost its bulk hardness due to recrystalization. Recrystalization studies revealed that recrystallization activation energy of Grade 2 CP titanium is in between 57 and 83 kJ/moI. Thermal oxidation resulted in formation of oxide layer with an oxygen diffusion zone beneath and leaded surface hardening. Kinetic studies conducted on thermally oxidized samples resulted in calculation of the activation energies for oxide layer thickening and oxygen diffusion in titanium as 75-225 and 122-204 kJ/mol, respectively, depending on the amount of cold work prior to thermal oxidation.
Açıklama
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2004
Anahtar kelimeler
Yeniden kristalleşme (Metalurji),
Titanyum alaşımları,
Recrystallization (Metallurgy),
Titanium alloys