The effect of heat treatment on toughness in nickel-based weld metal in the 600--900 C temperature range

Journal Article · Sat Jan 01 04:00:00 EST 1994 · Welding Journal (Miami); (United States)

OSTI ID:5363033

Nilsson, J O; Lundquist, B; Lonnberg, M ^[1]

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1. AB Sandvik Steel, Sandviken (Sweden)

The effect of aging on impact toughness in the temperature range 600--900 C has been examined in Type ER NiCr-3 weld metal according to AWS A5.14. It was found that a toughness minimum occurred after aging for 10,000 h at 700 C. A toughness loss was also observed after aging for 10,000 h at 600 C although it was less pronounced than at 700 C (1,292 F). Microstructural investigations showed that copious precipitation occurred at 600 and 700 C. The toughness minimum observed in material aged at 700 C is ascribed to the unfavorable geometry of the precipitates formed at this temperature, leading to high stress concentrations. It is of prime importance during welding to avoid embrittling phases such as martensite. This can be achieved by using a weld metal that is rich in nickel, which suppresses the formation of martensite. One example of a nickel-base weld metal that is suitable for this purpose is Sanicro 72, which is the specification of ER NiCr-3 according to AWS A5.14. Although the as-received weld is tough, having an impact toughness of typically 220 J (163 ft-lb) at room temperature, experience has shown that some embrittlement occurs after long-term service at elevated temperatures. However, phenomena that could be related to the observed decrease in ductility such as reduced fatigue life at 593 C/1,098 F and premature creep failures at 566 C/1,051 F in ER NiCr-3 weld metal have been reported. Furthermore, fracture toughness tests of Alloy 718 weld metal have shown that [delta]-phase formed during aging at 566 C causes a decrease in toughness. The purpose of the present paper is to describe the microstructural changes occurring in ER NiCr-3 weld metal in order to obtain a deeper understanding of the aging-induced decrease in ductility.

• OSTI ID: 5363033
• Journal Information: Welding Journal (Miami); (United States), Journal Name: Welding Journal (Miami); (United States) Vol. 73:1; ISSN 0043-2296; ISSN WEJUA3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
CHROMIUM ALLOYS
DATA
EXPERIMENTAL DATA
FILLER METALS
INFORMATION
JOINTS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
NUMERICAL DATA
WELDED JOINTS