VCS ile Yer Tutucu Üre Kullanılarak Üretilen Gözenekli NiAl Parçalara Soğuk Sıkıştırma Basıncının Etkisi

Öz

Gözenekli NiAl parçalar hacimce %20, 40, 60 oranında yer tutucu üre parçacıkları kullanılarak elde edilmiştir. Kullanılan üre partikül boyutu 150-300 µm aralığındadır. Nikel, alüminyum, önceden oluşturulmuş NiAl tozları ve üre partiküllerinden oluşan karışımlara soğuk presle 50, 100, 200 ve 300 MPa basınçlar uygulanmıştır. Farklı soğuk sıkıştırma basıncıyla üretilen parçaların boyutları, makro yapısı, mikro yapısı ve basma dayanımı hacim yanma sentezi (HYS) sonrasında analiz edilmiştir. Çalışmanın amacı farklı üre miktarlarına sahip numunelerde HYS sonrası en yakın boyutsal değişimi sağlayan soğuk sıkıştırma basıncını belirlemektir. Bu numuneler daha sonraki bir çalışmada çok katmanlı bir parça oluşturmak için kullanılacaktır. VCS sırasında farklı katmanların boyut değişimindeki yüksek fark, çatlamaya ve ayrılmaya yol açacağından, çok katmanlı parça tasarımında farklı katmanlar için benzer boyut değişikliği gereklidir. 300 MPa basınçla soğuk preslenen numunelerin bazen soğuk presleme veya VCS sonrası kalıptan çıkarıldıktan sonra çatlaklar içerdiği görülmüştür. Bu nedenle bu parçalar karakterizasyona tabi tutulamamıştır. VCS sonrası en yakın boyut değişimi ve daha yüksek basınç dayanımı değerleri, farklı üre içerikli numunelerde 200 MPa'da soğuk preslendiğinde elde edilmiştir. En yüksek ortalama basınç dayanımı (218,8±29,5 MPa), %20 üre parçacıklarıyla hazırlanan ve 200 MPa ile soğuk sıkıştırılan numunede elde edilmiştir.

Anahtar Kelimeler

• NiAl
• yanma sentezi
• boşluk oluşturucu metodu
• gözenekli intermetalik

Effect of Cold Compaction Pressure on Porous NiAl Articles Produced by Using Space Holder Urea via VCS

Abstract

Porous NiAl samples were obtained by using 20, 40, 60 vol.% space holder urea particles. The urea particle size was in the range of 150-300 µm. Pressures of 50, 100, 200 and 300 MPa were applied by cold press to the mixtures formed by nickel, aluminum, preformed NiAl powders and urea particles. The dimensions, macrostructure, microstructure and compressive strength of the parts produced with different cold compaction pressures were analyzed after volume combustion synthesis (VCS). The aim of the study is to determine the cold compaction pressure which provides the closest dimensional changes after VCS, in samples having different urea amounts. These samples will be used for forming a multi-stack article in a further study. Since a high difference in dimensional change of different layers during VCS will lead to cracking and separation, similar dimensional change is required for different layers in a multi-stack sample design. The samples which were cold pressed with 300 MPa pressure sometimes contained cracks after they were taken out of the die after cold pressing or after VCS. Therefore, they could not be subjected to characterization. The closest dimensional change and higher compressive strength values after VCS were obtained in samples having different urea contents, when they were cold pressed at 200 MPa. The highest mean compressive strength (218.8±29.5 MPa) was attained in the sample which was prepared with 20% urea particles and which was cold compacted with 200 MPa.

Keywords

• NiAl
• Combustion synthesis
• Space holder method
• Porous intermetallic

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