The role of aluminum on the weldability and sulfidation behavior of iron-aluminium cladding
- Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering
- Oak Ridge National Lab., TN (United States)
Single-pass welds and multiple-pass cladding of Fe-Al alloys were deposited on carbon steel substrates using the gas tungsten arc and gas metal arc welding processes. The effect of alloy composition on cold cracking susceptibility was assessed using a dye penetrant technique. The high-temperature (600 C) sulfidation behavior of low-Al alloys (5--10 wt.% Al), which exhibited good weldability, was examined using a thermogravimetric balance in a moderately reducing 0.1% H{sub 2}S--3.0% H{sub 2}-bal. Ar gas. Microstructural characterization was conducted by light optical microscopy, scanning electron microscopy, electron probe microanalysis and Knoop hardness testing. By varying the welding parameters, a range of dilution levels was achieved that resulted in fusion zone compositions with 3--30 wt.% Al. Under these processing conditions, cracking of the Fe-Al cladding is directly related to the aluminum concentration within the deposit. Cracking of the cladding was seen to have occurred by both inter- and transgranular modes for deposits containing greater than 10 wt.% Al. Below this composition limit, cracking did not occur. According to the Fe-Al phase diagram, this composition indicates the microstructural transition from the single-phase region of disordered solid solution ({alpha}) to the two-phase region of {alpha} + ordered Fe{sub 3}Al. The ordered structures of Fe{sub 3}Al and FeAl have been found to be more susceptible to environmental embrittlement, which has been seen to be the source of the cladding cracking problem, in terms of sulfidation behavior, alloys containing 5--10 wt.% Al exhibited corrosion rates significantly lower than carbon steel and 304 stainless steel. The results of this work indicate that Fe-Al cladding containing 5--10 wt.% Al shows potential promise for applications requiring a combination of weldability and sulfidation resistance in moderately reducing environments.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 320975
- Journal Information:
- Welding Journal, Vol. 78, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Iron aluminide weld overlay coatings for boiler tube protection in coal-fired low NOx boilers
High temperature sulfidation behavior of low Al iron-aluminum compositions