scholarly journals Deposição a Laser de Superliga à Base de Cobalto sobre Aço Inoxidável Austenítico

2021 ◽  
Vol 26 ◽  
Author(s):  
Marcelo T. Veiga ◽  
Leandro J. da Silva ◽  
Alexsandro Rabelo ◽  
Moisés F. Teixeira ◽  
Paulo R. A. Bloemer ◽  
...  
Keyword(s):  
Stellite 6

Resumo: O presente trabalho teve como objetivo determinar parâmetros de processamento a laser para deposição de revestimentos de Stellite 6 livres de descontinuidades e com geometria adequada sobre aço inoxidável austenítico. Revestimentos foram depositados com uma fonte de laser de diodo, equipada com um cabeçote coaxial contínuo, utilizando diferentes potências do feixe e velocidades de varredura. A geometria (largura, altura, ondulação e diluição) dos revestimentos foi medida por meio de análise da secção transversal. Esses dados obtidos foram utilizados para a modelagem do processo (superfície de resposta) e para estimar parâmetros otimizados (função desejabilidade), que foram posteriormente verificados experimentalmente. A microestrutura dos revestimentos depositados com os parâmetros otimizados foi caracterizada por microscopia óptica e eletrônica de varredura. A seleção adequada dos parâmetros resultou em revestimentos com bom acabamento, livre de descontinuidades superficiais e baixa diluição. Os resultados mostram que a potência do laser teve efeito significativo sobre a diluição, enquanto a velocidade influenciou na altura da camada depositada. A microestrutura resultante do revestimento é composta por dendritas ricas em cobalto e a região interdendrítica com carbonetos de cromo. Os resultados de dureza estão de acordo com o previsto na literatura.

scholarly journals Effect of Nitrogen Ion Implantation on the Cavitation Erosion Resistance and Cobalt-Based Solid Solution Phase Transformations of HIPed Stellite 6

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2324
Author(s):  
Mirosław Szala ◽  
Dariusz Chocyk ◽  
Anna Skic ◽  
Mariusz Kamiński ◽  
Wojciech Macek ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Ion Implantation ◽  
Phase Transformations ◽  
Erosion Rate ◽  
Cavitation Erosion ◽  
Matrix Phase ◽  
Nitrogen Ion Implantation ◽  
Stellite 6 ◽  
Nitrogen Ion

From the wide range of engineering materials traditional Stellite 6 (cobalt alloy) exhibits excellent resistance to cavitation erosion (CE). Nonetheless, the influence of ion implantation of cobalt alloys on the CE behaviour has not been completely clarified by the literature. Thus, this work investigates the effect of nitrogen ion implantation (NII) of HIPed Stellite 6 on the improvement of resistance to CE. Finally, the cobalt-rich matrix phase transformations due to both NII and cavitation load were studied. The CE resistance of stellites ion-implanted by 120 keV N+ ions two fluences: 5 × 1016 cm−2 and 1 × 1017 cm−2 were comparatively analysed with the unimplanted stellite and AISI 304 stainless steel. CE tests were conducted according to ASTM G32 with stationary specimen method. Erosion rate curves and mean depth of erosion confirm that the nitrogen-implanted HIPed Stellite 6 two times exceeds the resistance to CE than unimplanted stellite, and has almost ten times higher CE reference than stainless steel. The X-ray diffraction (XRD) confirms that NII of HIPed Stellite 6 favours transformation of the ε(hcp) to γ(fcc) structure. Unimplanted stellite ε-rich matrix is less prone to plastic deformation than γ and consequently, increase of γ phase effectively holds carbides in cobalt matrix and prevents Cr7C3 debonding. This phenomenon elongates three times the CE incubation stage, slows erosion rate and mitigates the material loss. Metastable γ structure formed by ion implantation consumes the cavitation load for work-hardening and γ → ε martensitic transformation. In further CE stages, phases transform as for unimplanted alloy namely, the cavitation-inducted recovery process, removal of strain, dislocations resulting in increase of γ phase. The CE mechanism was investigated using a surface profilometer, atomic force microscopy, SEM-EDS and XRD. HIPed Stellite 6 wear behaviour relies on the plastic deformation of cobalt matrix, starting at Cr7C3/matrix interfaces. Once the Cr7C3 particles lose from the matrix restrain, they debond from matrix and are removed from the material. Carbides detachment creates cavitation pits which initiate cracks propagation through cobalt matrix, that leads to loss of matrix phase and as a result the CE proceeds with a detachment of massive chunk of materials.

scholarly journals Experimental Studies of Stellite-6 Hardfaced Layer on Ferrous Materials by Tig Surfacing Process

2020 ◽  
Vol 998 ◽  
pp. 012061
Author(s):  
C Dinesh Chandra ◽  
B Rushikesh ◽  
Mohammed Numan ◽  
B Venkatesh
Keyword(s):  
Experimental Studies ◽  
Stellite 6

Investigation of the properties and characteristics of a hardfacing of Stellite 6 + Al 2 O 3 made by the GTAW-P process

2019 ◽  
Vol 1 (1) ◽  
pp. 015025
Author(s):  
Eduardo Ferracin Moreira ◽  
João Roberto Sartori Moreno ◽  
Paulo Cezar Moselli ◽  
Nadine Carla Pepe
Keyword(s):  
Stellite 6

Deterioration of Local Mechanical Properties of HVOF-Sprayed Stellite 6 after Exposure to High-Temperature Corrosion

2015 ◽  
Vol 662 ◽  
pp. 115-118 ◽  
Author(s):  
Zdeněk Česánek ◽  
Jan Schubert ◽  
Šárka Houdková ◽  
Olga Bláhová ◽  
Michaela Prantnerová
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperature Corrosion ◽  
Corrosion Testing ◽  
Time Interval ◽  
Coating Properties ◽  
Operational Conditions ◽  
Stellite 6 ◽  
Coating Surface ◽  
Before And After

Coating properties determine its behavior in operation. The simulation of future operational conditions is therefore the best quality test. The evaluation during operation is usually not possible to perform, and the coatings are therefore frequently characterized by their physical or mechanical properties. This text deals with the high temperature corrosion of HVOF sprayed Stellite 6 coating and with changes of its local mechanical properties before and after the corrosion testing. High temperature corrosion is defined as a corrosion in the presence of molten salts. In this case, the mixture of salts in composition of 59% Na2(SO)4 with 34.5% KCl and 6.5% NaCl was used. Two exposure temperatures 525 °C and 575 °C were selected and the tests for both temperatures were performed in the time interval of 168h in the autoclave. The coating with salt mixture layer was analyzed using scanning electron microscopy and nanoindentation. The high temperature resistance of Stellite 6 coating was evaluated according to the changes in the coating surface and by the occurrence of individual phases formed on the coating surface during the test. Generally, it can be said that the Stellite 6 alloys deposited by HVOF technology show selective oxidation under the salt film. This fact was also proved in this study. Furthermore, the nanoindentation measurements of Stellite 6 coating were performed before and after the corrosion testing. These measurements were used to evaluate the change of local mechanical coating properties.

Modeling and optimization of the turning parameters of cobalt alloy (Stellite 6) based on RSM and desirability function

2018 ◽  
Vol 100 (9-12) ◽  
pp. 2945-2968 ◽  
Author(s):  
Riadh Saidi ◽  
Brahim Ben Fathallah ◽  
Tarek Mabrouki ◽  
Salim Belhadi ◽  
Mohamed Athmane Yallese
Keyword(s):  
Desirability Function ◽  
Cobalt Alloy ◽  
Modeling And Optimization ◽  
Stellite 6
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