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Akımsız kaplama yöntemiyle Ni-B-TiO2 kompozitlerinde tribolojik özelliklerin geliştirilmesi

Improvement of tribological properties in Ni-B-TiO2 composites by electroless coatings method

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  1. Tez No: 1017219
  2. Yazar: OSMAN HARDAL
  3. Danışmanlar: PROF. DR. HATEM AKBULUT
  4. Tez Türü: Yüksek Lisans
  5. Konular: Metalurji Mühendisliği, Metallurgical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2026
  8. Dil: Türkçe
  9. Üniversite: Sakarya Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: Belirtilmemiş.

Özet

Bu tez çalışmasında, Ni–B–TiO2 kompozit kaplamalar akımsız kaplama yöntemi kullanılarak düşük karbonlu yumuşak çelik olan St 37 altlık malzeme üzerine başarıyla uygulanmıştır. Nano boyutlu TiO₂ partikülleri, kaplama banyosu içerisinde homojen bir dağılım sağlanması amacıyla ultrasonik karıştırıcı yardımıyla hazırlanmış ve kaplamalar 5, 10, 15 ve 20 g/L olmak üzere dört farklı TiO2 konsantrasyonunda üretilmiştir. Elde edilen kaplamaların yüzey ve kesit morfolojileri, elementel bileşimleri ve faz yapıları; alan emisyonlu taramalı elektron mikroskobu (FESEM), enerji dağılımlı X-ışını spektroskopisi (EDS) ve X-ışını kırınımı (XRD) analizleri ile karakterize edilmiştir. FESEM analizleri, kaplama yüzeyinde karnabahar benzeri bir morfoloji oluştuğunu ve TiO2 partiküllerinin genel olarak homojen dağıldığını göstermiştir. Bununla birlikte, artan TiO2 konsantrasyonu ile aglomerasyon eğilimi ortaya çıkmış ve yüzey topografisinin düzensizleştiği belirlenmiştir. EDS analizleri, TiO2 partiküllerinin kaplama matrisi içerisinde başarılı şekilde dağıldığını doğrulamıştır. Kesit incelemeleri, kaplamanın altlık üzerinde sürekli bir tabaka halinde geliştiğini ve sütunsal bir mikroyapı sergilediğini ortaya koymuştur. XRD analizleri ise kaplamaların yarı kristalin yapı karakterine sahip olduğunu göstermiştir. Mikrosertlik ölçümleri sonucunda kaplamaların yaklaşık 1000 HV sertlik değerine ulaştığı ve en yüksek sertliğin 15 g/L TiO2 ilavesinde elde edildiği belirlenmiştir. Bu durum, partiküllerin matris içerisinde optimum dağılım göstermesi ile ilişkilendirilmiştir. Aşınma testleri sonucunda, en düşük aşınma hızı ve en uygun sürtünme katsayısının yine 15 g/L TiO2 konsantrasyonunda elde edildiği tespit edilmiştir. Daha yüksek konsantrasyonlarda (özellikle 20 g/L) aglomerasyonun tribolojik performansı olumsuz etkilediği belirlenmiştir. Baskın aşınma mekanizmasının abrasif aşınma olduğu ortaya konulmuştur. Bu bulgular, TiO2 ilavesinin belirli bir optimum konsantrasyona kadar Ni–B kaplamaların mikroyapısal bütünlüğünü iyileştirerek mekanik ve tribolojik özelliklerini geliştirdiğini ve aşınma direncini önemli ölçüde artırdığını göstermektedir. Bu çalışmadan elde edilen sonuçlar, Ni–B–TiO2 kompozit kaplamaların geliştirilmesi ve endüstriyel uygulamalarda kullanımına yönelik önemli bir temel oluşturabileceğini göstermektedir. Bu kaplama sistemlerinin, özellikle yüksek aşınma direnci gerektiren otomotiv, havacılık, enerji ve savunma sanayi gibi alanlarda potansiyel kullanım imkânı sunabileceği değerlendirilmektedir. Ayrıca, farklı partikül türleri ve proses parametrelerinin incelenmesiyle performanslarının daha da iyileştirilebileceği öngörülmektedir.

Özet (Çeviri)

Surface engineering is an interdisciplinary field that investigates the interactions of materials with other materials and their surrounding environments and aims to control these interactions. It focuses on improving surface properties to enhance performance, extend service life, and provide cost-effective solutions. Today, surface engineering plays a critical role in various engineering fields such as aerospace, automotive, energy, defense, and biomedical applications. Damage and performance degradation in engineering components generally initiate at the surface. Surface-related mechanisms such as wear, corrosion, oxidation, and friction are the primary factors that directly affect the service life of materials. Surface engineering has a history as old as the structural materials used by humanity. Throughout history, particularly until the early 1970s, surface engineering practices were developed largely unconsciously. Today, it is recognized as one of the most effective approaches for optimizing engineering products in terms of quality, performance, reliability, and life-cycle cost. One of the main advantages of this approach is the ability to improve only the surface properties without altering the bulk material. However, in some applications, disadvantages such as high equipment costs, difficulties in process control, and adhesion problems between the coating and substrate may also arise. Various surface modification and coating methods are employed to improve the surface properties of engineering materials. These methods are generally classified into two main categories: processes that modify surface metallurgy and processes that alter surface chemistry. Surface metallurgy modification techniques include induction hardening, flame hardening, and laser hardening, while chemical modification techniques include diffusion-based processes such as carburizing, nitriding, and boriding. In addition, coating techniques such as electroplating, electroless plating, physical vapor deposition (PVD), and chemical vapor deposition (CVD) are widely used to enhance material performance. Surface engineering applications have a wide range of industrial uses. They are widely employed in sectors such as automotive, aerospace, energy, biomedical, and defense industries to improve resistance against wear, corrosion, and high-temperature effects. In this respect, surface engineering offers a strategic approach by enhancing the performance of existing materials while reducing the need for developing new ones. Electroless nickel coatings are an important surface coating method that enables deposition through chemical reduction reactions without the use of electrical current. Depending on the reducing agent used, these coatings are classified into two main groups: nickel–phosphorus (Ni–P) and nickel–boron (Ni–B) coatings. While Ni–P coatings are known for their high corrosion resistance, Ni–B coatings stand out due to their high hardness and wear resistance, making them particularly suitable for applications subjected to severe tribological conditions. Ni–B coatings are typically produced using reducing agents such as sodium borohydride or dimethylamine borane (DMAB) and generally contain approximately 0.5–6 wt.% boron. These coatings can achieve hardness values in the range of 9001200 HV and are therefore suitable for applications requiring high hardness and wear resistance. Furthermore, the formation of boride phases after heat treatment contributes to further improvements in hardness and mechanical durability. Nano-sized titanium dioxide (TiO2), typically with a particle size below 100 nm, exists in anatase, rutile, and brookite phases and is widely used as a reinforcing phase in coating systems due to its high surface area and reactivity. The incorporation of TiO2 particles into the Ni–B matrix enhances hardness and wear resistance, restricts dislocation motion, and promotes the formation of a fine-grained microstructure. This results in a significant improvement in the mechanical performance of the coating while also contributing to enhanced surface stability. Ni–B–TiO2 coatings are prominent as an environmentally friendly composite coating system, offering uniform coating capability and improved tribological performance. However, they also exhibit certain limitations, such as relatively low deposition rates and the requirement for precise control of process parameters. Despite these limitations, they may be considered a promising alternative for advanced surface engineering applications. In this study, Ni–B–TiO2 composite coatings were deposited on St 37 low-carbon steel substrates using the electroless plating method. The coatings were produced at four different TiO2 concentrations: 5, 10, 15, and 20 g/L. The surface and cross-sectional morphologies, elemental compositions, and phase structures of the coatings were analyzed using FESEM, EDS, and XRD techniques. FESEM analyses revealed that TiO2 particles formed a characteristic cauliflower-like morphology on the coating surface and were generally distributed homogeneously. However, increasing TiO2 concentration led to particle agglomeration and a more irregular surface topography. EDS results confirmed that TiO2 particles were successfully incorporated into the coating. Cross-sectional observations showed that the coating developed as a continuous layer and exhibited a columnar microstructure. XRD analyses indicated that the coatings possessed a semi-crystalline structure. Microhardness measurements performed under loads of 25 gf and 50 gf showed that the coatings reached approximately 1000 HV, with the highest hardness obtained at 15 g/L TiO2 concentration. This behavior may be associated with the optimal dispersion of reinforcing particles within the matrix and their contribution to load-bearing capacity. Wear tests conducted under a load of 2 N, at a sliding speed of 10 cm/s, using a 10 mm diameter alumina ball over a sliding distance of 500 m at 25 °C indicated that the lowest wear rate and the most favorable friction coefficient were achieved at 15 g/L TiO2 addition. At higher concentrations, particularly 20 g/L, agglomeration negatively affected the tribological performance by disrupting surface continuity. The dominant wear mechanism was identified as abrasive wear, and the microstructural features induced by TiO2 particles played a significant role in this behavior. In conclusion, Ni–B–TiO2 composite coatings appear to provide an effective surface engineering solution with high hardness and improved wear resistance. The incorporation of TiO2 particles, particularly at an optimal concentration, may significantly enhance the microstructural and tribological properties of the coatings. The results obtained from this study suggest that Ni–B–TiO2 composite coatings may provide a valuable basis for further development and potential industrial applications. It is considered that these coating systems could offer potential advantages in sectors such as automotive, aerospace, energy, and defense, where high wear resistance is required. Furthermore, more comprehensive investigations on different particle types, concentrations, and process parameters may contribute to further improvement of coating performance. In this context, Ni–B–TiO2 composite coatings may be regarded as a promising alternative for advanced surface engineering applications.

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