Sermetel and Alseal

SermeTel® Process 5380 DPTM Coating System

SermeTel Process 5380 DP (Dense Pack) consists of a closely packed aluminum-filled chromate/phosphate basecoat, sealed with a chemically inert chromate phosphate topcoat. The coating provides excellent protection to stainless steel and ferrous alloys, and will operate at temperatures up to 1200°F (650°C).

Advantages

Process 5380 DP should be used on any component where serious concerns are corrosion/erosion protection, tight tolerances, surface finish, or where the potential for media entrapment is possible due to part configuration. On dimensionally critical surfaces, precision coating thicknesses of as thin as 0.3 mils (7.5 µm) can be achieved.

The main features are:

  • Does not require media finishing to achieve final surface finish
  • Compressibility supports mating surfaces
  • Excellent corrosion resistance
  • Excellent surface finish

Applications

The aerodynamic finish of Process 5380 DP makes it ideal for any gas path turbine component, such as compressor blades, vane and shroud assemblies, and diffusers. Similar SermeTel topcoated systems have seen millions of hours of successful service in military, commercial aviation and industrial turbines.

Specifications

Flight Turbine:
Pratt Whitney Aircraft PWA 110-21/-9
Pratt Whitney Canada CPW 420

Ground Turbine:
Westinghouse 83342NU
Dresser Rand 015-009-022
Solar ES59-263 Type B, Type C
European Gas Turbines 525202

Physical Properties

Thickness
0.3 to 5.0 mils (7.5 to 127µm),
typically 1.5 mils (37.5µm)

Surface Profile
<10 µinches @.10"
cutoff on new flight components
(.25 µm @ 0.3mm)

<25 µinches @.30" cutoff on new IGT gas path surfaces
(.63 µm @ 0.8mm)

Performance Data

(2 mil (50 &*181;m) coating on 1010 steel)

Test Results
Salt Spray
(ASTM B117)
No red rust on panels after
2500 hours of testing
Abrasion
Resistance
(ASTM D968)
>300 liters/mil
Tensile Bond
Strength
(ASTM C633)
> 8,000 psi (70 MPa) strain
rate: 0.1 inch per minute

SermaLoy™ J

SermaLoy J is a diffused slurry aluminide coating with a unique silicon-enriched outer layer. It is effective in protecting gas turbine hot section components at temperatures up to 1835°F (1000°C).

Benefits of SermaLoy J include:

  • Excellent resistance to both high and low temperature hot corrosion (LTHC and HTHC)
  • Excellent resistance to high temperature oxidation
  • Excellent resistance to particulate erosion
  • Compatibility with most nickel and cobalt based superalloys, as well as austenitic stainless steels
  • Flexibility of diffusion processing that eliminates the need for resolutioning/precipitation/aging heat treatments

SermaLoy J is an intermetallic nickel aluminide with a silicon-enriched outer layer. The presence of silicon on the surface of the coating promotes the formation of a tightly adherent scale of very pure aluminum oxide (Al2O3) that is very resistant to dissolution by the liquid sulfate salts that cause hot corrosion. The excellent high temperature oxidation resistance of SermaLoy J is due in part to reduced oxygen mobility through the pure alumina as well as to the stabilizing effect that the silicon has upon the aluminde.

Silicon in SermaLoy J also helps prevent thermal fatigue cracking. Thermally induced strains caused by unequal rates of heating and cooling of the surface and interior of a component are a common cause of degradation in conventional alummide coatings. Cracking almost always originates within these coatings and propagates into the base metal. In SermaLoy J, if cracking does occur, it tends to be arrested at the inter-diffusion zone and does not propagate into the substrate.

With the SermaLoy J slurry aluminizing process, each component is coated individually, thus each can be inspected before diffusion. At this intermediate stage, repair or rework of the slurry coating can be accomplished without any loss of base metal. Using a slurry also greatly simplifies masking and allows selective coating of very localized regions – which is ideal for repair – or alternatively, large areas like ducts and burner cans.

SermaLoy J slurry aluminide on WaspaLoy (diffused at 1625°F (885°C) for 2 hours). Backscatter electron image, 1000X.

The SermaLoy J slurry aluminde can be formed between 1600°F and 1835°F (870°C and 1000°C). Diffusion cycles may be tailored to each alloy and application. Expensive resolutioning, precipitation, and aging treatments can be avoided by diffusing around 1600°F (870°C). This relatively low diffusion temperature not only eliminates the microstructure changes associated with high temperature aluminizing processes, but also allows brazed components to be refurbished without risking damage to the brazed joints.

Semaloy J Concentration profile
   

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