Borlama işlemi uygulanmış Inconel 718 süperalaşımın mikroyapı, aşınma ve mekanik özelliklerinin incelenmesi

Yıl 2021, Cilt: 11 Sayı: 1, 61 - 72, 09.06.2021

Hüseyin Duran , Derviş Özkan , Cahit Karaoğlanlı

Öz

Bu çalışmada, yüksek korozyon direnci ve sürünme dayanımı olan ancak düşük yüzey sertliğinden dolayı tribolojik uygulamalarda kullanımı sınırlı olan Inconel 718 Ni-esaslı süperalaşımının borlama ile aşınma dirençlerinin iyileştirilmesi çalışılmıştır. Inconel 718 altlık malzemesine 950°C’de EKabor 2 tozu ortamında 4, 8 ve 16 saatlik süreli periyotlarda kutu borlama işlemi uygulanmıştır. Borlama prosesi sonucunda numunelerde oluşan fazlar ve meydana gelen kaplama tabakasının malzemenin metalografi ve mekanik özelliklerine olan etkisinin incelenmesi amacıyla taramalı elektron mikroskobu (SEM), optik mikroskop analizi, X-ışınları difraksiyonu (XRD) analizi, mikrosertlik ölçümleri ve aşınma testleri gerçekleştirilmiştir. Aşınma testleri işlemsiz Inconel 718 ve farklı sürelerde borlanmış numunelere farklı yükler (3N, 5N, 10N ve 15N) altında, ileri-geri (reciprocating) aşınma testi uygulanarak aşınma yüzey profilleri elde edilmiş ve aşınma performansları karşılaştırmalı olarak incelenmiştir. Numunelerin sıralı sertlik değerleri belirlenmiştir. Karakterizasyon incelemeleri sonucunda Ni2Si, Ni4B4 ve FeB fazından oluşmuş kaplama tabakaları elde edilmiştir. Aşınma testleri sonucunda aşınma dayanımı en iyi olan numunenin 950°C’de 4 saatlik borlama süresine tabi tutulan numune olduğu ve aşınma mekanizmalarının abrasif aşınma olduğu tespit edilmiştir. En iyi aşınma direncinin 950°C’de 4 saat süre ile borlanan numunede elde edilmiş olması en sert ve en iyi nüfuziyet gösteren kaplama tabakasının bu parametrede elde edilmesinin bir sonucu olarak ortaya çıkmıştır.

Anahtar Kelimeler

Inconel 718, superalaşım, borlama, aşınma, mikroyapısal özellikler

Investigation of microstructure, wear and mechanical properties of boronized Inconel 718 superalloy

Öz

In this study, the wear resistance of Inconel 718 Ni-based superalloy, which has high corrosion and creep resistance but has limited use in tribological applications due to its low surface roughness was improved via boriding method. Pack-boriding process was applied on Inconel 718 substrate material at 950°C using Ekabor 2 powder for 4, 8 and 16 hour boriding periods. Scanning electron microscopy (SEM), optical microscopy analysis, X-ray diffraction (XRD) analysis, microhardness measurements and tribological tests were performed to assess the effect of resulting phases and coating layer on the metallographic and mechanical properties of the borided speciments. In this study, Inconel 718 superalloy substrate was pack borided with boron and coal dust at 950° C for 4, 8 and 16 h. The phases formed in the samples as a result of the boronizing process and the effects of boron layer on the mechanical properties of the material were investigated. Reciprocating wear tests were applied under varying loads (3N, 5N, 10N and 15N) on the non-borided and borided samples and their wear performances were comparatively evaluated. The specimens’ hardness ranking was determined. As a result of the characterization studies, layers consisting of Ni2Si, Ni4B4 and FeB were detected. The sample with the best wear resistance was the one subjected to a boronizing time of 4 h at 950°C. This result was further supported by the finding that, the hardest layer exhibiting the best diffusion behavior belonged to this sample. This was attributed to the formation of a uniform boride layer in the vertical direction from the surface and the high hardness of this layer.

Anahtar Kelimeler

Inconel 718, superalloy, boronizing, wear, microstructural properties

Kaynakça

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