02
2025
Authors: Ziya Özgür Yazıcı, Aytekin Hitit, Hakan Şahin
Title: Crystallization of CoWB ternary boride in nickel-based metallic glass
Journal of Non-Crystalline Solids
Volume 650, 15 February 2025, 123343
Metallic glass team of Novaltec is pleased to share our newly published article on the thermal processing of Ni-CoWB based composites, using Ni-based metallic glass precursor as the starting material. For the first time, the crystallization kinetics of CoWB ternary boride in a Ni-based metallic glass precursor were studied. Additionally, the continuous heating temperature diagram of a Ni-based amorphous alloy with ternary boride precipitation ability is investigated for the first time. It is demonstrated that CoWB crystals are stably protected within the microstructure without transforming into another crystal phase. The results of the study are considered beneficial for estimation the basic parameters in thermal (HVOF) coating, laser cladding, and heat treatment applications of CoWB reinforced nickel coatings. Maybe in additive manufacturing?
The crystallization kinetics of CoWB ternary boride were investigated through non-isothermal differential scanning calorimetry experiments, using a Ni-based metallic glass precursor as the starting material. The effects of isothermal heat treatment temperature on the phase evolutions were also systematically studied. The results showed that the melt crystallization and glass crystallization behaviors of the alloy differ from each other. The continuous heating transformation diagram plotted from non-isothermal analyses is consistent with the results of isothermal heat treatments. A broad ternary boride precipitation zone was demonstrated, involving the gradual precipitation of CoWB crystals. Avrami exponent values for the early crystallization stage showed that the crystallization mechanism of CoWB is governed by the interface-controlled three-dimensional growth mechanism, and nucleation rate is high. As the crystallization progresses, a diffusion-controlled growth occurs and the nucleation rate decreases. This study offers insights into the heat treatment of CoWB-reinforced nickel matrix nanocomposites, benefiting future research and industrial production processes.
12
2024
PCT Application
Inventors: Aytekin Hitit, Ziya Ozgur Yazıcı, Hakan Şahin
Patent Title: Nickel (Ni) - Cobalt (Co) - Molybdenum (Mo) - Boron (B) Containing Bulk Metallic Glass Alloys
Date of Application: December 28th, 2024
12
2024
Inventors: Aytekin Hitit, Ziya Ozgur Yazıcı, Hakan Şahin
Patent Title: Nickel (Ni) - Cobalt (Co) - Molybdenum (Mo) - Boron (B) Containing Bulk Metallic Glass Alloys
Novaltec is excited to announce a new patent application for "Nickel (Ni) - Cobalt (Co) - Molybdenum (Mo) - Boron (B) Containing Bulk Metallic Glass Alloys." The metallic glass alloys developed in this invention will be used as precursors for the production of CoMoB-reinforced composites. The composites formed through the crystallization of Ni-Co-Mo-B metallic glass alloys exhibit high fracture toughness due to the precipitated nickel, as well as superior hardness and wear resistance due to the ultra-hard CoMoB phase.The manufacturing process we utilize offers several distinct advantages over traditional sintering methods used in the production of carbide and boride-reinforced composites:
1. Complex Geometries: Our method allows for the creation of composite parts with intricate geometries that are often challenging to produce using conventional sintering techniques. We can achieve this by melting, casting, and subsequently heat treating the materials.
2. Flexibility in Design: For complex shapes, we can first produce parts with simpler geometries through melting and casting. These parts can then be refined using thermoplastic forming to achieve the desired design. This two-step approach enhances design flexibility.
3. Advanced Coatings: Our atomized alloy powders can also be utilized to produce high-performance hard coatings through thermal spray coating methods and laser cladding. Unlike conventional cermet coatings, where the binder phase limits hardness, our approach enables complete melting of the powders, resulting in fully dense coatings without compromising hardness or wear resistance.
4. Additive Manufacturing: We can produce composite parts with desired geometries using atomized alloy powders through additive manufacturing. This method not only supports the production of complex shapes but also optimizes material usage and reduces waste.
5. Efficient Sintering Process: By using amorphous powders produced through atomization, we can perform sintering using techniques such as vacuum hot-pressing or spark plasma sintering (SPS). This allows for simultaneous consolidation of the powders and formation of the composite structure without the need for pre-mixing binders. As a result, we achieve fully dense structures at lower sintering temperatures compared to traditional composites.
09
2024
Inventors: Aytekin Hitit, Ziya Ozgur Yazıcı, Hakan Şahin, Pelin Öztürk Aşgın
Patent Title: Nickel-Based Bulk Metallic Glass Alloys Containing High Amount of Refractory Metal and Boron
Patent No: US12098451B2
Date of Patent: September 24th, 2024
08
2022
Authors: Ziya Ozgur Yazıcı, Aytekin Hitit, Hakan Şahin, Muhammet Emir Kara
Title: Crystallization and thermal stability of Ni-based metallic glass with high tungsten and boron
Journal of Non-Crystalline Solids
Volume 590, 15 August 2022, 121679
Non-isothermal crystallization behavior of the amorphous (Ni51W31.6B17.4)75Co25 alloy with high tungsten and boron content was investigated. Continuous heating DSC analyses of the amorphous samples revealed that the alloy undergoes crystallization with three-step. The thermal stability and crystallization kinetics of the samples were evaluated by Lasocka, Kissinger and Ozawa approaches. Activation energy calculated for the first crystallization step showed that the thermal stability of the NiCoWB alloy is higher than other Ni-based alloys. Avrami exponent value calculated for the early stage of the Niss-phase crystallization indicated a three-dimensional diffusion-controlled mechanism with increasing nucleation. The continuous heating transformation diagram plotted according to non-isothermal analyzes is consistent with the phases detected in isothermal heat treatments. The usability of the continuous heating transformation diagram of the alloy in isothermal heat treatment applications has been demonstrated.