While INCONEL 718 is one of the most highly utilized Ni-base superalloys, this alloy has high sensitivity to hydrogen embrittlement. Hydrogen cracking tends to occur at the surface of stress concentrated regions. A laser irradiation can locally solutionize such surface regions and reduce the hardness. Therefore, this laser surface solutionizing is effective in preventing hydrogen cracking of INCONEL 718 with little sacrifice of the strength of structures. In the present work, a 2.5kW CO2 laser has been applied to surface solutionizing of INCONEL 718. The solutionized zones, where the age precipitates of γ′ and γ″ were dissolved in the matrix, could be obtained at the surface of INCONEL 718 without melting the treated zones by controlling the defocus distance and traverse speed. The hardness of the laser solutionized zones was reduced to below 250Hv from the base metal hardness of approximately 450Hv. The depths of the surface solutionized zones increased with the defocus distance. The surface solutionized zone with more than 1mm in depth was obtained without melting in an optimum condition. The ductility of the surface solutionized specimen was almost twice that of the base metal in a tensile test under a 29.4MPa hydrogen atmosphere at room temperature with hydrogen pre-charging.

1.
Edited by
M. J.
Donachie
, Jr
(
1984
).
Superalloys Source Book
,
ASM
,
Metal Park, Ohio
. pp.
47
400
.
2.
S.
Fukuyama
,
K.
Yokogawa
,
M.
Araki
,
Y.
Koyari
,
H.
Aoki
and
Y.
Yamada
. “
Fatigue Crack Growth Properties of Ni-Base Alloys in High Pressure Hydrogen at Room Temperature
.”
J. Soc. Mater. Sci. Jpn.
. Vol.
38
: (May,
1989
). pp.
539
545
.
3.
S.
Fukuyama
,
K.
Yokogawa
,
M.
Araki
,
Y.
Koyari
and
Y.
Yamada
. ‘
Tensile Properties of Ni-Base Alloys in High Pressure Hydrogen at Room Temperature
.”
J. Soc. Mater. Sci. Jpn.
. Vol.
40
: (June,
1991
). pp.
736
742
.
4.
S.
Fukuyama
,
K.
Yokogawa
,
Y.
Yamada
and
T.
Iida
. “
Hydrogen Embrittlement of Ni-Base Superalloys Used for H-II Rocket Engine
.”
Tetsu to Hagane
. Vol.
78
: (June,
1992
). pp.
860
869
.
5.
M.
Sundararaman
,
P.
Mukhopadhyay
and
S.
Banerjee
. “
Some Aspects of the Precipitation of Metastable Intermetallic Phases in INCONEL 718
.”
Metall. Trans.
. Vol.
23A
: (July,
1992
). pp.
2015
2028
.
6.
Ya-fang
Han
,
P.
Deb
and
M. C.
Chaturvedi
. “
Coarsening Behaviour of γ″- and γ′-particles in Inconel Alloy 718
.”
Metal Sci.
. Vol.
16
: (December,
1982
). pp.
555
561
.
This content is only available via PDF.
You do not currently have access to this content.