Mark L Harper

US Patent:

53646592, Nov 15, 1994

Filed:

Sep 3, 1993

Appl. No.:

8/116302

Inventors:

Robert A. Rapp - Columbus OH
Mark A. Harper - Columbus OH

Assignee:

Ohio State University Research Foundation - Columbus OH

International Classification:

C23C 1600

US Classification:

427253

Abstract:

Diffusion coatings incorporating approximately 18 to 35 wt % Cr and 1 to 3% Si in 2. 25Cr-1. 0Mo steel and 1018 steel have been produced using a pack cementation method. The codeposition of these concentrations of Cr and Si into the 2. 25Cr-1. 0Mo and 1018 steel requires the use of a "mixed activator" (fused salt solution of NaF and NaCl). Cyclic oxidation tests in air at 700. degree. C. of a coated 2. 25Cr-1. 0Mo steel coupon with a surface concentration of 34Cr-3Si have shown excellent cyclic oxidation resistance. Furthermore, a 1018 coupon coated to a surface concentration of Fe-30 wt % Cr-3Si shows negligible aqueous corrosion in an aerated 3. 5% NaCl solution at room temperature. These coatings have provided similar protection in more complex oxidizing and reducing atmospheres.