Factors contributing to the strength of a polycrystalline nickel–cobalt base superalloy

2011 ◽  
Vol 64 (9) ◽  
pp. 892-895 ◽  
Author(s):  
Toshio Osada ◽  
Nobuo Nagashima ◽  
Yuefeng Gu ◽  
Yong Yuan ◽  
Tadaharu Yokokawa ◽  
...  
Keyword(s):  
Polycrystalline Nickel ◽  
Nickel Cobalt ◽  
Cobalt Base ◽  
Base Superalloy

Cobalt-Base Superalloy Coating Using GTAW Process

2013 ◽  
Vol 758 ◽  
pp. 41-47
Author(s):  
Fernanda de Souza de Souza Royse ◽  
Ivan Napoleão Bastos ◽  
Hector Reynaldo Meneses Costa
Keyword(s):  
Welding Process ◽  
Metallographic Analysis ◽  
Welding Parameters ◽  
Low Alloy Steels ◽  
Properties Of Coatings ◽  
Operational Conditions ◽  
Gtaw Process ◽  
Alloy Steels ◽  
Cobalt Base ◽  
Base Superalloy

In harsh operational conditions, the low-alloy steels need to be protected from the environment. Thus, against corrosion and wear, an ordinary choice is metallic cladding. In this sense, the present study aimed to evaluate the properties of cobalt base superalloy coating deposited by gas tungsten welding process (GTAW) on steel SAE 4140. A circumferential weld was chosen due to its critical restraint. Four coating conditions were studied varying the welding currents. A microstructural evaluation was done using optical and scanning electron microscopy. The physical properties of coatings were additionally evaluated by microhardness measurement and dilution quantification. The results obtained indicated, for all conditions, a uniformity of layers. However, the deposited weld characteristics are strongly dependent on welding parameters. For the welding parameters studied, the maximum dilution of 60.8% was observed in coatings with austenitic and dendrite microstructures welded with 110 A current. Moreover, the metallographic analysis and microhardness tests showed, for some cases, the presence of partially diluted zone, a microstructural layer in the transition region of base metal and coating. The welding performed with current of 90 A showed the best combination of microhardness and dilution aspects, without defects in coating.

Influence of type and morphology of carbides on stress-rupture behavior of a cast cobalt-base superalloy

2017 ◽  
Vol 728 ◽  
pp. 145-151 ◽  
Author(s):  
Weimin Gui ◽  
Hongyu Zhang ◽  
Min Yang ◽  
Tao Jin ◽  
Xiaofeng Sun ◽  
...  
Keyword(s):  
Stress Rupture ◽  
Cobalt Base ◽  
Base Superalloy ◽  
Rupture Behavior

scholarly journals Grain Refinement of a Powder Nickel-Base Superalloy Using Hot Deformation and Slow-Cooling

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1978 ◽  
Author(s):  
Xianqiang Fan ◽  
Zhipeng Guo ◽  
Xiaofeng Wang ◽  
Jie Yang ◽  
Jinwen Zou
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Hot Deformation ◽  
Nickel Base Superalloy ◽  
Polycrystalline Nickel ◽  
Slow Cooling ◽  
Homogeneous Microstructure ◽  
Average Grain Size ◽  
Nickel Base ◽  
Base Superalloy

A pre-hot-deformation process was applied for a polycrystalline nickel-base superalloy to active deformation twins and dislocations, and subsequent slow cooling treatment was used to achieve grain refinement and microstructure homogenization. The microstructural evolution of the alloy was investigated, and the corresponding underlying mechanism was discussed. It was found that twinning mainly occurred in large grains during pre-hot-deformation owing to the stress concentration surrounding the large grains. High density dislocations were found in large grains, and the dislocation density increased approaching the grain boundary. The average grain size was refined from 30 μm to 13 μm after slow cooling with a standard deviation of grain size decreasing from 10.8 to 2.8, indicating a homogeneous microstructure. The grain refinement and microstructure homogenization during cooling process could be achieved via (i) static recrystallization (SRX), (ii) interaction of twin tips and γ’ precipitates, and (iii) grain coarsening hindered by γ’ precipitates in grain boundaries.

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