Prakt. Met. Sonderband 46 (2014) 241
MICROSTRUCTURE-PROPERTIES CORRELATIONS IN
SIMILAR WELDS OF ALLOY 617
M. Speicher, R. Scheck, K. Maile
Material Testing Institute (MPA), University of Stuttgart, Stuttgart, Germany
ABSTRACT
In this work the microstructure of similar welds of a nickel base alloy 617 has been
investigated. The effect of a post weld heat treatment (PWHT) at 980 °C for 3 h on the
microstructure and properties of selected welded joints was examined. Short-term creep
tests were carried out at 700 °C on as-welded and heat treated material and characterize
by using optical (OM) and transmission electron microscope (TEM). It could be shown, that
the PWHT causes changes in the deformation and damage behaviour of seams. Here,
respective correlations could be made to the microstructure of individual weld areas.
1. INTRODUCTION
Alloy 617 belongs to the group of candidate materials for use in high-efficiency steam
power plants [1, 2]. So far, this commercial alloy has been mainly used in the field of gas
turbine and in the chemical industry for thin-walled structures. However, till now only
limited experience in terms of the behaviour and the operation of the thick-walled
components exist. Since the welding is an essential processing step in the power plant
and plant engineering, the characterizing of the behaviour of the welded joints is decisive.
In COMTES program [3], in which the welded thick-walled components made of Alloy 617
were investigated in a test loop in field trials, many seams fail after a relatively short
operation time. Therefore, it is important to determine characteristic properties of the
seams also in a short-term range.
2. EXPERIMENTAL WORK
2.1 MATERIAL
The chemical composition of base material (BM) and weld metal (WM) used for the welded
joint and investigated in this work is shown in Tab. 1. The specimens have been machined
from a pipe (Da: 500 x 30 mm) manufactured using the Erhardt process. After machining
the girth weld was produced using TIG orbital process,
Tab. 1: Chemical composition of Alloy 617 (wt.%)
© | cr Co | Mo | A | Ti | Fe | B Ni
Base Material | 0.060 | 21.95 12.0 | 8.60 042 | 071 | 00036 | Bal
Weld Metal 0.051 "9009 | 110 | 894 | 126 | 031 0.76 | 0.0033 Bal.
