Study of Microstructure in Surface-Melted Region of Ni-Base Single Crystal Superalloy CMSX-4

2006 ◽  
Vol 512 ◽  
pp. 313-318 ◽  
Author(s):  
Yoshihiro Fujita ◽  
Kazuyoshi Saida ◽  
Kazutoshi Nishimoto

This work investigated microstructure in the surface-melted region of Ni-base single crystal superalloy CMSX-4 by using a diode laser beam as a heating source. Such processing parameters as laser power and scanning speed in laser surface melting were varied while defocusing distance and shielding gas (Ar) flow rates were fixed. Specimen surfaces were arranged parallel to the (001) of base alloy. The microstructure in the melted region was analyzed by optical microscopy and SEM. Crystal orientation of the melted region was analyzed using electron backscattered pattern analysis. The microstructure was remarkably changed when the heat input of surface melting was varied. The surface-melted region was found to solidify into a single crystal with directional dendrites that grew along the [001] directions under low heat input conditions. The surface-melted region was also a single crystal with disoriented dendrites that grew along the [100] or [010] directions under medium heat input conditions. In contrast, the melted region consisted of poly crystals with stray crystals under high heat input conditions. Such tendencies were also observed in the melted region with gas tungsten arc. These results demonstrate that the surface-melted region can solidify into a single crystal under conditions in which larger temperature gradient and higher solidification rates can be achieved.

2013 ◽  
Vol 747-748 ◽  
pp. 797-803 ◽  
Author(s):  
Li Wu Jiang ◽  
Shu Suo Li ◽  
Mei Ling Wu ◽  
Ya Fang Han

The grain competitive growth and elimination during the directional solidification of a Ni3Al-base single crystal superalloy IC6SX prepared by spiral grain selection method was studied systematically. The experimental results revealed that there were 5 kinds of mechanism during the grain competitive growth and elimination. The grains with preferred growth direction and smaller deviation angle to growth direction have stronger competitiveness, and the mutual thwarting of dendrites played an important role in the processing of grains competitive growth. The results can explain the competitive growth mechanism during the directional solidification and can be used to optimize processing parameters to lay an important foundation for improving preparation processes of single crystal superalloys.


2008 ◽  
Vol 26 (1) ◽  
pp. 80-87
Author(s):  
Yoshihiro FUJITA ◽  
Kazuyoshi SAIDA ◽  
Kazutoshi NISHIMOTO ◽  
Toshiaki FUSE

2021 ◽  
Vol 1041 ◽  
pp. 47-56
Author(s):  
Zhi Guo Gao

The contribution of crystallography-dependent metallurgical factors, such as supersaturation of liquid aluminum and minimum dendrite tip undercooling, to solidification behavior and microstructure development is numerically analyzed during Ni-Cr-Al ternary single-crystal superalloy molten pool solidification to better understand thermodynamic and kinetic driving forces behind solidification cracking resistance. The variation of supersaturation of liquid aluminum and minimum dendrite tip undercooling with location of solid/liquid interface is symmetrically consistent in (001)/[100] welding configuration. By comparison, the variation is asymmetrically consistent in (001)/[110] welding configuration. The different distribution is attributed to growth crystallography and dendrite selection. Significant increase of supersaturation of liquid aluminum and dendrite tip undercooling from [010] dendrite growth region to [100] dendrite growth region preferentially aggravates microstructure development as result of nucleation and growth of stray grain formation with the same heat input on each half of the weld pool in (001)/[110] welding configuration. High heat input (both increasing laser power and decreasing welding speed) exacerbates supersaturation of liquid aluminum and dendrite tip undercooling by faster diffusion to incur stray grain formation with severity of contributing thermometallurgical factors for susceptibility to solidification cracking, while low heat input (both decreasing laser power and increasing welding speed) ameliorates microstructure development and increases resistance to solidification cracking. Weld microstructure of optimum welding conditions, such as combination of low heat input and (001)/[100] welding configuration, is less susceptible to solidification cracking to suppress asymmetrical microstructure development and improve weld integrity potential rather than insidious welding conditions, such as combination of high heat input and (001)/[110] welding configuration. Severer supersaturation of liquid aluminum and wider dendrite tip undercooling occur in the [100] dendrite region as consequence of alloying enrichment, while smaller supersaturation of liquid aluminum and narrower dendrite tip undercooling occur in the [001] dendrite region as consequence of alloying depletion to spontaneously facilitate epitaxial growth of single-crystal essential. Symmetrical (001)/[100] welding configuration decreases growth kinetics of dendrite tip with smaller overall supersaturation of liquid aluminum and dendrite tip undercooling than that of asymmetrical (001)/[110] welding configuration regardless of combination of laser power and welding speed. Mitigation of supersaturation of liquid aluminum and dendrite tip undercooling simultaneously alleviate crack-susceptible microstructure development and solidification cracking. Additionally, the appropriate mechanism of solidification cracking resistance improvement through modification of crystallography-dependent supersaturation and undercooling of dendrite tip is proposed. Calculation analyses are sufficiently explained by experiment results in a reasonable way. The additional purpose of this theoretical analysis is to evaluate solidification cracking susceptibility of similar nickel-based or iron-based single-crystal superalloys.


2008 ◽  
Vol 26 (1) ◽  
pp. 88-96
Author(s):  
Yoshihiro FUJITA ◽  
Kazuyoshi SAIDA ◽  
Kazutoshi NISHIMOTO ◽  
Toshiaki FUSE

2012 ◽  
Vol 445 ◽  
pp. 697-701
Author(s):  
M. Heydarzadeh Sohi ◽  
S. Shahbazi ◽  
A. Halvaee

In this study tungsten inert gas (TIG) surface melting of pre- plasma sprayed WC-14%Co low carbon steel has been studied. Surface melting was performed under different heat inputs by using various TIG parameters including intensity and kind of current. Microstructure and microhardness of surface alloyed specimens were then studied. Eutectic structures containing tungsten-rich carbides were shaped in a matrix including martensite lath, when high heat input was used. Decreasing at heat input affected the microstructure of the alloyed layers, and high amount of faceted tungsten-rich carbides (Fe3W3C) were formed in fairly low heat input. Microhardness of melted layers highly improved in comparison with that of the substrate.


2014 ◽  
Vol 1028 ◽  
pp. 90-95 ◽  
Author(s):  
Chun Cheng Zang ◽  
Yan Zhong Wang ◽  
Yi Du Zhang

Nickel-base alloy powder is widely applied to strengthen the surface of products through laser processing. This paper presents the experiments on laser cladding of Ni45 alloy powder on substrates of 45 steel. The experimental results show that the laser cladding processing parameters such as laser power, scanning speed, powder feed rate and overlap ratio have great effects on the qualities of the cladding layer. Optimizing the processing parameters is an effective way to improve the layer qualities and obtain desired cladding layers.


2018 ◽  
Vol 34 (8) ◽  
pp. 1315-1324 ◽  
Author(s):  
Guowei Wang ◽  
Jingjing Liang ◽  
Yanhong Yang ◽  
Yu Shi ◽  
Yizhou Zhou ◽  
...  

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