Effect of Low-Angle Boundary on Microstructure and Stress Rupture Property of a Third Generation Single Crystal Superalloy DD10

The microstructure of a third generation single crystal superalloy DD10 with 0°~15° grain boundary and stress rupture property at 980°C/280MPa and 1100°C/140MPa have been studied and compared in the present investigation. The results showed that the primary dendritic stems at either side of low angle boundary indicated angular differences as compared with structure of principal [001] crystal. After thermal treatment, the grain boundary changed from irregular chain structure of γ’ and γ to flat and thin γ layer. Under the condition of 980°C/280MPaand 1100°C/140MPa, stress rupture life of the DD10 alloy with 7° low angle boundary decreased little compared with [001] crystal. The rupture was non-intergranular fracture. The 9° low angle boundary did not have a remarkable effect on stress rupture property of the DD10 alloy.

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Effect of Heat Treatment on Microstructure and Mechanical Properties for a Ni3Al Base Single Crystal Alloy DDIC6

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.1443 ◽

2007 ◽

Vol 546-549 ◽

pp. 1443-1446 ◽

Cited By ~ 1

Author(s):

Zhi Gang Kong ◽

Lei Ji ◽

Shu Suo Li ◽

Ya Fang Han ◽

Hui Bin Xu

Keyword(s):

Heat Treatment ◽

Single Crystal ◽

Rupture Life ◽

Stress Rupture ◽

Constant Load ◽

Heat Treatment Condition ◽

Stress Rupture Life ◽

Stress Rupture Property ◽

Single Crystal Alloy ◽

Proper Size

The effect of heat treatment on microstructures and stress rupture property of a Ni3Al base single crystal alloy DDIC6 was studied in the present investigate. The single crystal specimens were produced by screw selection crystal method. The heat treatment for the alloy was 1300°C/10h+1120°C/4h+870°C/32h and 1300°C/10h+870°C/32h.The microstructures were examined by SEM, TEM and X-ray EDS techniques. The stress rupture tests were carried out in air by constant load creep machines under 1100°C/130MPa with the specimens size of φ5×25 mm. The experimental results showed that the as-cast large size γ′ phases entirely dissolved after 1300°C/10h, and secondary fine γ′ phases precipitated by following aging at 1120°C and 870°C for certain periods of time. The stress rupture life under 1100°C/130MPa increased from 20~30hrs for as-cast condition to 60~100hrs for heat treatment condition. The improvement of the creep resistance of the alloy may attribute to the decrement of the elements segregation at dendrite and interdendritic areas, and the proper size and distribution of γ′ phases.

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Effect of Minor Elements on the Grain Boundary Strengthening of a Single Crystal Superalloy RR2072

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.124-126.1405 ◽

2007 ◽

Vol 124-126 ◽

pp. 1405-1408

Author(s):

D.H. Kim ◽

Y.S. Yoo ◽

Chang Yong Jo ◽

C.N. Jones

Keyword(s):

Grain Boundary ◽

Single Crystal ◽

Rupture Life ◽

Stress Rupture ◽

Thermal Exposure ◽

Single Crystal Superalloy ◽

M23c6 Carbide ◽

Carbide Formation ◽

Minor Elements ◽

Grain Boundary Strengthening

Effect of carbon and boron on the grain boundary strengthening of a second generation single crystal superalloy RR2072 was investigated. Single crystal and bicrystal specimen with three kinds of tilt type misorientation angle were grown by Bridgman technique. Creep and stress rupture tests were conducted at 950oC and 1050oC. Rupture life of single crystal of the alloy modified with carbon and boron was comparable to that of the RR2072 which is free from boron and carbon. TCP phase precipitation such as sigma was suppressed in the modified alloy during thermal exposure and creep deformation. Rupture life of the modified alloy bicrystal was superior to that of the RR2072 bicrystal. M23C6 carbide formation and suppression of γ′ band growth is thought to be the role of minor elements for the grain boundary strengthening of a nickel base single crystal superalloy RR2072.

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Influence of Withdrawal Rate on Tensile and Stress Rupture Properties of the Single Crystal Superalloy DD9

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.625 ◽

2013 ◽

Vol 747-748 ◽

pp. 625-628 ◽

Cited By ~ 2

Author(s):

Z.X. Shi ◽

J.R. Li ◽

Shi Zhong Liu

Keyword(s):

Single Crystal ◽

Rupture Life ◽

Stress Rupture ◽

Single Crystal Superalloy ◽

Withdrawal Rate ◽

Stress Rupture Life ◽

The Third ◽

Stress Orientation ◽

Stress Rupture Properties ◽

Rupture Properties

The third generation single crystal superalloy DD9 was processed with different withdrawal rates and the effect of withdrawal rate on the tensile and stress rupture properties of the alloy was investigated. The relation between the mechanical properties and microstructure of the alloy with different withdrawal rates was discussed. The results showed that the withdrawal rate had a little effect on the tensile properties at 25 of the alloy. The tensile strength at 980 and stress rupture life at 1120/140MPa of DD9 alloy all increased with the increasing of withdrawal rate. The γ precipitates of specimen tensile at 25 had a little extension in the stress orientation. The extension of γ precipitates in the stress orientation at 980 was much more than that at 25. The vertical γ matrix at 980 became thinner and horizontal γ matrix became thicker slightly. The γ precipitates of those had rafted in a direction transverse to the applied stress.

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Stress Rupture Properties of the Second Generation Single Crystal Superalloy DD6 after High Temperature Exposure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.1249 ◽

2007 ◽

Vol 546-549 ◽

pp. 1249-1252 ◽

Cited By ~ 2

Author(s):

Hai Peng Jin ◽

Jia Rong Li ◽

Shi Zhong Liu

Keyword(s):

High Temperature ◽

Single Crystal ◽

Second Generation ◽

Rupture Life ◽

Stress Rupture ◽

Single Crystal Superalloy ◽

Stress Rupture Life ◽

Stress Rupture Properties ◽

Temperature Exposure ◽

Rupture Properties

The effects of high temperature exposure simulating service conditions on stress rupture properties were studied for the second generation single crystal superalloy DD6. The specimens with [001] orientation were exposed in air at temperatures of 980°C and 1070°C for 100h to 1000h. They were then tested using conventional mechanical tests at 1070°C/140MPa to determine the effects of exposure on stress rupture properties. The analysis indicated that stress rupture life decreased with increasing exposure time. At the temperature of 980°C, the stress rupture life is more than 180h after exposure for 1000h. When the test temperature increased to 1070°C, the stress rupture life exceeds 100h after 800h exposure. The morphology of γ prime phase after exposure was observed by using scanning electron microscopy (SEM). Morphologies evaluations have shown that alloy DD6 exhibits excellent microstructure stability after exposure. TCP (Topologically Closed Packed) phases have not been observed. It has been also found that the morphology and size of γ prime affected stress rupture life of the alloy. The decrement in stress rupture life with increasing exposure is a result of γ prime rafting.

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Influences of W and Al on the Microstructure and Stress-Rupture Property of Re-Free Ni-Based Single Crystal Superalloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.492 ◽

2017 ◽

Vol 898 ◽

pp. 492-497

Author(s):

Jing Yang Chen ◽

Qing Li ◽

Ming Jun Zhang ◽

Xin Tang ◽

Cheng Bo Xiao

Keyword(s):

Single Crystal ◽

Volume Fraction ◽

Base Alloy ◽

Rupture Life ◽

Solidus Temperature ◽

Stress Rupture ◽

Stress Rupture Life ◽

Stress Rupture Property ◽

Matrix Channel ◽

Liquidus Temperatures

The influence of W and Al on the solidus and liquidus temperatures, microstructure and stress-rupture property at 980 °C/250 MPa was investigated in three Re-free experimental Ni-based single crystal superalloys. The results indicated that the solidus temperature increased for 14.0 °C and 9.8 °C by adding 0.84 wt.% W only and adding 0.45 wt.% Al and 0.44 wt.% W to the base alloy, respectively. The γ′ morphology changed from nearly cuboidal in the base alloy to cuboidal by adding 0.45 wt.% Al and 0.44 wt.% W. The volume fraction of γ′ precipitates increased, while the γ channel width decreased after adding Al and W. The additions of Al and W improved the stress-rupture life at 980 °C/250 MPa because of higher γ′ volume fraction, narrower γ matrix channel and more complete rafting structure.

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