Simultaneous chromizing-aluminizing coating of low-alloy steels by a halide-activated, pack-cementation process

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00664491· OSTI ID:5619490

Geib, F D; Rapp, R A ^[1]

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1. Ohio State Univ., Columbus, OH (United States)

The simultaneous chromizing aluminizing of low-alloy steels has achieved Kanthal-like surface compositions of 16-21Cr and 5 8wt.% AI by the use of cementation packs with a Cr Al masteralloy and an NH[sub 4]Cl activator salt. An initial preferential deposition of Al into the alloy induces the phase transformation from austenite to ferrite at the 1150[degrees]C process temperature. The low solubility of carbon in ferrite results in the rejection of solute C into the austenitic core, thereby presenting the formation of an external Cr-carbide layer, which would otherwise block aluminizing and chromizing. The deposition and rapid diffusion of Cr and Al into the external bcc ferrite layer follows. Parabolic, cyclic-oxidation kinetics for alumina growth on the coated steels in air were observed over a wide range of relatively low temperatures (637-923[degrees]C). 20 refs., 9 figs., 1 tab.

• OSTI ID: 5619490
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 40:3-4; ISSN OXMEAF; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALLOYS
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AUSTENITE
CARBIDES
CARBON ADDITIONS
CARBON COMPOUNDS
CEMENTITE
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM
COATINGS
CORROSION
DEPOSITION
DIFFUSION COATING
ELEMENTS
FERRITE
INTERMETALLIC COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
IRON CARBIDES
IRON COMPOUNDS
KINETICS
LOW ALLOY STEELS
METALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROTECTIVE COATINGS
REACTION KINETICS
STEELS
SURFACE COATING
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS