Research Papers

Diffusible Hydrogen Level in Deposited Metal and Their Effect on Tensile Properties and Flexural Strength of P91 Steel

[+] Author and Article Information
Chandan Pandey

Department of Mechanical and
Industrial Engineering,
Indian Institute of Technology Roorkee,
Uttrakhand 247667, India
e-mails: chandanpy.1989@gmail.com; chandan.pndy@rediff.com

M. M. Mahapatra

School of Mechanical Sciences,
Indian Institute of Technology,
Bhubaneswar, Odisha 751013, India

Pradeep Kumar, N. Saini

Department of Mechanical and
Industrial Engineering,
Indian Institute of Technology Roorkee,
Uttrakhand 247667, India

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received October 16, 2016; final manuscript received December 15, 2016; published online March 23, 2017. Assoc. Editor: Hareesh Tippur.

J. Eng. Mater. Technol 139(3), 031004 (Mar 23, 2017) (11 pages) Paper No: MATS-16-1293; doi: 10.1115/1.4035764 History: Received October 16, 2016; Revised December 15, 2016

In a “very high-temperature reactor” (VHTR), the Nb–V-modified 9Cr–1Mo creep strength enhance the ferritic (CSEF) steel which is the chosen material for fabrication of reactor pressure vessels and piping because of its excellent high temperature thermal and mechanical properties. In such CSEF steel weldments, the hydrogen-induced cracking (HIC) is a critical issue. In the present work, the different levels of hydrogen have been induced in P91 CSEF weld metal to study their effect on HIC. The HIC susceptibility of P91 steel welds has been studied by carrying out the tensile test and flexural test for the different level of diffusible hydrogen. The hydrogen levels in deposited metals have been measured by using the mercury method. The fracture tensile and flexural test samples have been characterized based on the field-emission scanning electron microscope (FE-SEM). It is concluded that higher the level of diffusible hydrogen in deposited metal, more is the susceptibility of P91 steel to HIC. The minimum flexural and tensile strength are 507.45 MPa and 282 MPa, respectively, for 12.54 ml volume of diffusible hydrogen in 100 g of deposited weld metal.

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Fig. 2

Schematic of hydrogen test assembly

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Fig. 3

(a) Hydrogen test assembly just after welding and (b) hydrogen test assembly after braking with run on and run off piece

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Fig. 4

Diffusible hydrogen measurement setup

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Fig. 5

Schematic of tensile specimen

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Fig. 6

Flexural test setup (a) photograph of the machine and (b) schematic arrangement of the specimen

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Fig. 7

(a) SEM image of as-received cast and forged P91 steel at different magnification (a) 5000×, (b) 50000×, and (c) optical micrograph showing tempered lath microstructure

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Fig. 1

Schematic representation of diffusible hydrogen to the HAZ through weld fusion zone [23]

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Fig. 8

Macrograph of the deposited metal sectioned from the fractured tensile specimen (a) case I and (b) case IV

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Fig. 9

Microstructure of weld fusion zone for case I, at different magnification (a) and (b), (c) CGHAZ

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Fig. 10

Microstructure of weld fusion zone for case IV, at different magnification (a) and (b)

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Fig. 11

Microstructure of various zone for case IV, (a) weld fusion zone, (b) CGHAZ, and (c) energy-dispersive X-ray spectroscopy (EDS) spectra of white particles (spot 1)

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Fig. 12

Engineering stress–strain curves

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Fig. 13

(a) Fractured flexural test specimen and (b) typical load displacement curve

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Fig. 14

Effect of diffusible hydrogen level on flexural strength and tensile strength of deposited metal

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Fig. 15

(a) Macroview of the tensile fractured surface for case I, (b) brittle weld zone, (c) ductile base metal, and (d) EDS spectra of EDS spot 1

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Fig. 16

(a) Macroview of the tensile fractured surface for case IV, (b) brittle weld zone, and (c) brittle base metal zone




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