Evaluation of coated and clad heat exchangers for syngas coolers. Volume 1. Evaluation of coating variability and weldability. [T-11 steel (1. 25 Cr-0. 05 Mo)]

Technical Report · Sat Feb 01 04:00:00 EST 1986

OSTI ID:6025481

Lewis, E C

The feasibility of coating large heat exchanger components made from low alloy steels for syngas coolers of coal gasification plants was studied. Diffused coatings applied by the pack cementation process were found the most promising. Waterwall panels and convection modules were aluminized and chromized to study the uniformity of the deposits. The thickness of commercially produced aluminized coatings was quite variable and occasionally unsatisfactory. The thickness of chromized coatings was also variable, but generally satisfactory as the coating in the thinnest areas still contained 25% Cr and was about 10 mils (250 ..mu..m) thick. Welding of chromized coatings was satisfactory. Welding of aluminized coatings caused cracking in the outer, high aluminum part of the coating. High temperature corrosion studies were carried out at 400/sup 0/C in syngas environments using aluminized and chromized coatings and stainless steel claddings on low alloy steels such as T-11 (11/4% Cr-0.5% Mo). Aluminized coatings were resistant to sulfidation when their aluminum content exceeded 16 to 18%. Intergranular corrosion occurred when cracks extended into the lower part of the coating, where the aluminum content was less than 18%. This happened especially adjacent to welded areas. Chromized coatings with a chrome content of 25% or more were also resistant to sulfidation. Some Intergranular corrosion of chrome depleted areas near carbide precipitates was noted, especially near welds. Chromized coatings on carbon stabilized alloys appeared completely resistant to sulfidation and contained few carbide precipitates. Stainless steel claddings generally had low sulfidation rates, especially Nb stabilized SS310 (25 Cr +- 20 Ni). 1 ref., 51 figs., 4 tabs.

• Research Organization: Combustion Engineering, Inc., Chattanooga, TN (USA)
• OSTI ID: 6025481
• Report Number(s): EPRI-AP-4406-Vol.1; ON: TI86920166
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404* -- Coal
Lignite
& Peat-- Gasification
36 MATERIALS SCIENCE
360101 -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
ALUMINIUM
CHEMICAL REACTIONS
CHROMIUM
CHROMIUM ALLOYS
COAL GASIFICATION PLANTS
COATINGS
COMPARATIVE EVALUATIONS
CORROSION
CORROSION RESISTANT ALLOYS
DATA
DIMENSIONS
ECONOMICS
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
HEAT EXCHANGERS
HEAT TREATMENTS
HIGH TEMPERATURE
INDUSTRIAL PLANTS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
JOINING
MATERIALS TESTING
METALLOGRAPHY
METALS
NUMERICAL DATA
PROTECTIVE COATINGS
STAINLESS STEELS
STEELS
SULFIDATION
TESTING
THICKNESS
TRANSITION ELEMENTS
WELDING