Influence of nanocrystalline nickel powder on oxidation resistance of spark plasma sintered Ni-17Cr6.5Co1.2Mo6Al4W7.6Ta alloy
- Authors: Babalola, Bukola Joseph , Maledi, Nthabiseng , Shongwe, Mxolisi Brendon , Bodunrin, Michael Oluwatosin , Obadele, Babatunde Abiodun , Olubambi, Peter Apata
- Date: 2020
- Subjects: Nickel based superalloy , Nanostructured , Spark plasma sintering
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/453453 , uj:40033 , Citation: Babalola, B.J. et al. 2020. Influence of nanocrystalline nickel powder on oxidation resistance of spark plasma sintered Ni-17Cr6.5Co1.2Mo6Al4W7.6Ta alloy. , DOI: https:// doi.org/10.1016/j.jksues.2019.01.002
- Description: Abstract: An investigation was carried out to evaluate the isothermal oxidation behavior of nickel based superal- loys at 1100 °C for 120 h. The alloys which were microstructured and nanostructured were developed by spark plasma sintering system. The oxidation test was carried out at a temperature of 1100 °C in air at different exposure time up to 120 h. The nanostructured nickel based alloy possessed better oxidation resistance with the formation of continuous adherent alumina, chromia scales, and spinel on the alloy surface and with no significant internal oxides. The oxidation rate of NiO was observed to be lower in the nanostructured nickel superalloy due to low diffusion rate of Nickel. The oxidation kinetics followed a parabolic oxidation law.
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Effect of scanning speed on laser deposited 17-4PH stainless Steel
- Authors: Bayode, Abiodun , Pityana, Sisa , Akinlabi, Esther Titilayo , Shongwe, Mxolisi Brendon
- Date: 2017
- Subjects: Functionaly graded material , Laser metal deposition , Mechanical property
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/237432 , uj:24324 , Citation: Bayode, A. et al. 2017. Effect of scanning speed on laser deposited 17-4PH stainless Steel.
- Description: Abstract: Laser metal deposition (LMD) is one of the additive manufacturing technologies that is used in the production of fully dense parts layer by layer. This innovative manufacturing process has the potential to reduce the weight, time and cost of manufacturing components. It is able to process different metallic powders and also produce custom alloy or functionally graded material by consolidating different metallic powders. The purpose of this study was to investigate and discuss the structural integrity, mechanical property and microstructure of 17-4 precipitation hardened stainless steel processed by laser metal deposition. In this study, the laser scanning speed was varied while other process parameters where kept constant. Material characterization was done using optical microscopy and Vickers indentation testing. The results show that, the processed material was structurally sound and defect free. The microstructure was predominantly martensitic and the laser scanning speed was observed to have an influence on the micro-hardness of the structure.
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Processing of pure titanium containing titanium-based reinforcing ceramics additives using spark plasma sintering
- Authors: Diouf, Saliou , Durowoju, Mondiu Olayinka , Shongwe, Mxolisi Brendon , Olubambi, Peter Apata
- Date: 2017
- Subjects: Spark plasma sintering , Titanium matrix composites , Ceramics
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/240416 , uj:24730 , Citation: Diouf, S. 2017. Processing of pure titanium containing titanium-based reinforcing ceramics additives using spark plasma sintering. Leonardo Electronic Journal of Practices and Technologies. 269-286. , ISSN: 1583-1078
- Description: Abstract: The densification behaviour, microstructural changes and hardness characteristics during spark plasma sintering of CP-Ti reinforced with TiC, TiN, TiCN and TiB2 were investigated. Commercially pure Ti powders were dry mixed with varied amounts (2.5 and 5 wt. %) of the ceramic additives using a T2F Turbula mixer for 5 h and at a speed of 49 rpm. The blended composite powders were then sintered using spark plasma sintering system (model HHPD-25 from FCT Germany) at a heating rate of 100oC min-1, dwell time of 5 min and sintering temperature of 950ºC. The sintering of CP-Ti was used as a base study to select the proper spark plasma sintering temperature for full density. Densification was monitored through analysis of the recorded punch displacement and the measured density of the sintered samples using Archimedes method. High densities ranging from 97.8% for 5% TiB2 addition to 99.6% for 5% TiCN addition were achieved at a relatively low temperature of 950°C...
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Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy
- Authors: Franklin, Ochonogor O. , Akinlabi, Esther Titilayo , Nyembwe, Kasongo D. , Pityana, Sisa , Shongwe, Mxolisi Brendon
- Date: 2016
- Subjects: Heat treatment , Titanium alloys
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/214859 , uj:21334 , Citation: Franklin, O.O. et al. 2016. Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy.
- Description: Abstract: A hybrid Ti-6Al-4V based metal matrix composites characterized of martensitic structure was formed using three hoper system. Different volume percentages used were as follows: 3.0 vol. % of Ti-6Al-4V, 3.2 vol. % of Ti-6Al-4V and 3.4 vol. % of Ti-6Al-4V respectively while an equal amount of BN and B4C mixed with the Ti-6Al-4V powder particle was fed through the hoper systems at a constant laser power 2000 W and scanning speed of 1.0 m/s. The influence of rapid cooling and varied powder particle at constant coating temperature on the surface morphology and hardness property of Ti-6Al- 4V/B4C/BN alloy systems was however investigated. The hardness result of experimental showed a general improvement. Further result showed that the Ti-6Al- 4V/B4C/BN system fabricated at 3.0 Ti Vol. percent had a hardness improvement as high as 986.9 HVO.5 compared to the as receive Ti-6Al-4V substrate Hardness value of about 357.3 HVO.5. 3.2 Ti Vol. percent systems recorded a hardness value of 723.4 HVO.5 and 3.2 Ti Vol. percent system recorded a hardness value of 609.6 HVO.5. Optical microscope (OM) Scanning electron microscope (SEM) was also carried out for microstructural evaluation and Energy Dispersive Spectroscopy (EDS) to confirm the elemental composition of coating when necessary.
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Tribocorrosion behaviours of AISI 310 and AISI 316 austenitic stainless steels in 3.5% NaCl solution
- Authors: Obadele, Babatunde Abiodun , Andrews, Anthony , Shongwe, Mxolisi Brendon , Olubambi, Peter Apata
- Date: 2016
- Subjects: Metals , Electrochemical techniques , Corrosion
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/123414 , uj:20788 , Citation: Obadele, B.A. et al. 2016. Tribocorrosion behaviours of AISI 310 and AISI 316 austenitic stainless steels in 3.5% NaCl solution.
- Description: Abstract: In this paper the tribocorrosion behaviours of AISI 310 and AISI 316 stainless steels have been studied under reciprocating sliding condition in 3.5% NaCl solution, using a pin-on-disk tribometer integrated with a potentiostat for electrochemical control. Different sliding loads were used at a constant rotational speed of 60 rpm. The results show that sliding load has significant effect on the tribocorrosion behaviour of both materials. Corrosion attack was severe at sliding load conditions in both materials suggesting corrosion-induced wear as the dominant of the two synergistic components. However, at low sliding load, anodic dissolution and pit formation in AISI 316 was accelerated by sliding action causing wear-induced corrosion to be dominant.
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Effects of ternary metal additions on corrosion of spark plasma sintered Ni-Fe alloys in H2SO4 and NaCl
- Authors: Shongwe, Mxolisi Brendon , Makena, Isaac Moraka , Ajibola, Olawale Olarewaju , Olubambi, Peter Apata , Adams, Feyisayo Victoria
- Date: 2018
- Subjects: Spark plasma sintering , Corrosion , Ni-Fe based alloy
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/279685 , uj:30039 , Citation: Shongwe, M.B. et al. 2018. Effects of ternary metal additions on corrosion of spark plasma sintered Ni-Fe alloys in H2SO4 and NaCl. Bulletin of the Chemical Society of Ethiopia, 32(2), 337-349. DOI: https://dx.doi.org/10.4314/bcse.v32i2.12 , ISSN 1011-3924
- Description: Abstract: Effect of ternary additions on electrochemical behavior of Ni-Fe binary alloys developed by Spark Plasma Sintering (SPS) were investigated and reported. All specimens revealed common passivity behavior in H2SO4. Both binary and ternary alloys did not reveal passivity region under saline conditions. The alloys have lower corrosion rates in NaCl than in H2SO4. Binary Ni50Fe50 alloy is characterized by large pits in H2SO4 and homogeneous corrosion on surface in NaCl. Ni50Fe40Ta10 shows better passivity in 1 M H2SO4 and Ni50Fe40Al10 has the lowest corrosion rate in 3.5 wt.% NaCl.
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A comparative study of spark plasma sintering and hybrid spark plasma sintering of W-4.9ni-2.1Fe heavy alloy
- Authors: Shongwe, Mxolisi Brendon , Diouf, Saliou , Durowoju, Mondiu Olayinka , Olubambi, Peter Apata , Ramakokovhu, Munyadziwa Mercy , Obadele, Babatunde Abiodun
- Date: 2016
- Subjects: Tungsten heavy alloys , Spark plasma sintering , Microstructure
- Type: Article
- Identifier: http://hdl.handle.net/10210/123454 , uj:20793 , Citation: Shongwe, M.B. et al. 2016. A comparative study of spark plasma sintering and hybrid spark plasma sintering of W-4.9ni-2.1Fe heavy alloy.
- Description: Abstract: Mixed 93W-4.9Ni-2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark plasma sintering (HSPS) techniques with 30 mm and 60 mm samples in both conditions. After SPS and HSPS, the 30 mm and 60 mm alloys (except 60mm-SPS) had a relative density (>99.2%) close to the theoretical density. Phase, microstructure and mechanical properties evolution of W-Ni-Fe alloy during SPS and HSPS were studied. The microstructural evolution of the 60 mm alloys varied from the edge of the sample to the core of the sample. Results show that the grain size and the hardness vary considerable from the edge to the core of sintered sample of 60 mm sintered using conventional SPS compared to hybrid SPS. Similarly, the hardness also increased from the edge to the core. The 60 mm-HSPS alloy exhibit improved bending strength than the 60 mm-SPS, 1115 MPa and 920 MPa respectively, former being similar to the 30 mm-SPS and HSPS alloys. The intergranular fracture along the W/W grain boundary is the main fracture modes of W-Ni-Fe, however in the 60 mm-SPS alloy peeling of the grains was also observed which diminished the properties. The mechanical properties of SPS and HSPS 93W-4.9Ni-2.1Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size and overall homogeneity.
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