PSI - Issue 16

Alexander Balitskii / Procedia Structural Integrity 16 (2019) 134–140

135

Alexander Balitski / StructuralIntegrity Procedia 00 (2019) 000 – 000

2

1. Introduction

Increasing of hydrogen containing gas working temperature on turbine inlet during last 50 years in 2 th – 5 th engine generation up to 1500…1600°C accompanied by improvement of heat resistant superalloys durability. During last decades many interesting results of the hydrogen influence on mechanical properties and crack resistance of metallic materials has obtained (for example) in Air Force Research Laboratory, University of Illinois, General Electric, Pratt & Whitney Power Systems, Air Liquide, University de Toulouse, Technische Universitat Dresden, Hydrogen Technology Research Center Kyushu University, Hitachi Ltd. and Karpenko Physico-Mechanical Institute NASU (Steffens et al. (2001), Furner et al. (2013), Gayduk (2012), Balitski et al. (2009a, 2009b, 2009c, 2014, 2016, 2018a, 2018b), Ming (2009), Dmytrakh (2011), Dmytrakh et al. (2010, 2013), Holländer et al. ( 2016), Gray (1974), Moody et al. (1985), Brown et al. (1966), Lee (2012), Dadfarnia et al. (2015), Barrera et al. (2018), Symons (2001), Syrotyuk et al. (2015), Delafosse et al. (2009)). The production of modern turbine equipment with higher operated temperatures requires the wide usage of heat-resistant Ni alloys and Ni single crystals. In such cases alloys are exploited at high temperatures in the contact with high pressure hydrogen containing gas. Therefore one of the most important requirements for modern nickel-cobalt super alloys is their resistance to hydrogen degradation, in other words their ability to keep high level of mechanical properties under the action of hydrogen in wide range of exploitation parameters (Steffens et al. (2001), Furner et al. (2013), Gayduk (2012), Balitskii et al. (2018a, 2018b)). General tendency in the nickel-based heat resistant super alloys capability increasing in comparison with base level – more complicated alloys composition (Steffens et al. (2001), Furner et al. (2013), Gayduk (2012)). It has been investigated the Ni-Co alloys (obtained from powder 0.1...0.3 mm under hot gaseous (in argon) isostatic pressure (up to 300 MPa) (Table 1, I, II ) (Firth Rixon Metal Ltd, Sheffield) and deformed (obtained by vacuum induced remealting) materials (Table 1, III, IV ) for gaseous turbine discs. Investigation has performed in the 25 … 800 °С temperatures ranges and hydrogen pressures up to 70 MPa on the special equipment described in (Balitskii et al. (2012)). 2. Materials and the experimental protocol

Table 1. Chemical composition of Ni-Co alloys modifications. Alloy

Chemical composition, wt. % С Cr Co Мo Ti

Al

W

Nb

Si

S

Р

Other

Ni60Co15Cr8W8Al2Mo3 ( І )

0.06 8.27 15.16 3.37 1.39 2.02 7.68 1.79 0.10 0.009 0.015 В0.01; Zr0.015; Mg0.02

Ni54Co15Cr9W7Al5Mo4 ( ІІ )

0.03 9.23 15.2 3.82 1.6

5.3

7.91 2.63 0.46 0.009 0.015 В0.01; Zr0.015; Mg0.02; Cu0.49; Hf0.40

Ni62Cr14Co10Mo5Nb3Al3Ti3 ( ІII )

0.06 13.98 10.02 5.22 2.59 2.59 0.08 2.59 0.14 0.005 0.006 В0.01; Zr0.01; La0.1 0.03 13.74 10.17 5.94 2.50 2.37 0.41 3.29 0.12 0.003 0.006 В0.01; Zr0.01; La0.1

Ni61Cr14Mo6Nb3Al2Ti3 ( ІV )

The structural feature of investigated Ni60Co15Cr8W8Al2Mo3 alloy composition is the appearance of initial powders borders that did not growth through of the re-crystallised grains. It is conditioned, mainly, on the fact that carbides particles have distinguished on the powders surfaces and prevent to complete of material consolidation. In the new version of Ni54Co15Cr9W7Al5Mo4 (ІІ) alloy has increased the content of carbide forming elements and the carbon concentration was decreased up to 0.03 wt. %. Addition of hafnium (Hf) admixture has formed the stable carbides (MeC), that allows to clean carbide nets from the initial powders borders and increase the cohesion energy of γ , γ' coherent phases ( Moody et al. (1985), Brown et al. (1966), Lee (2012), Dadfarnia et al. (2015), Barrera et al. (2018), Symons (2001), Delafosse et al. (2009),