A method for converting an existing steam methane reformer (SMR) to produce hydrogen via ammonia cracking is provided. The method can include the steps of: providing the existing SMR, wherein the SMR was formerly used to produce hydrogen from a hydrocarbon feedstock; and improving the nitridation resistance of the inner surface of the equipment by adding a protective layer to an inner surface of equipment to be used in the existing SMR, wherein the equipment is selected from the group consisting of a catalyst tube, feed piping, a feed preheater, process gas heat exchangers, and combination thereof.

A method for converting an existing steam methane reformer (SMR) to produce hydrogen via ammonia cracking is provided. The method can include the steps of: providing the existing SMR, wherein the SMR was formerly used to produce hydrogen from a hydrocarbon feedstock; and improving the nitridation resistance of the inner surface of the equipment by adding a protective layer to an inner surface of equipment to be used in the existing SMR, wherein the equipment is selected from the group consisting of a catalyst tube, feed piping, a feed preheater, process gas heat exchangers, and combination thereof.

A method of applying a protective coating to an article comprises the steps of a) depositing aluminum in a surface region of an article, and b) depositing chromium is the surface region of the article subsequent to step a), whereby at least a portion of the chromium replaces at least a portion of the aluminum. Another method and an article are also disclosed.

A method of applying a protective coating to an article comprises the steps of a) depositing aluminum in a surface region of an article, and b) depositing chromium is the surface region of the article subsequent to step a), whereby at least a portion of the chromium replaces at least a portion of the aluminum. Another method and an article are also disclosed.

A fuel rod cladding (4) for a light water reactor includes a core (16) including a matrix consisting of pure molybdenum or of a molybdenum-based alloy; and an outer protective layer (18). The outer protective layer (18) is selected among a chromium-based coating (20) deposited on an outer surface of the core (16) that includes at least one chromium-based coating layer (24) consisting of pure chromium or of a chromium-based alloy; a chromium-based diffusion layer (22) obtained by diffusion of chromium into the core (16) from the outer surface of the core (16); or a succession of a chromium-based diffusion layer (22) obtained by diffusion of chromium into the core (16) from the outer surface of the core (16) and a chromium-based coating (20) consisting of chromium or of a chromium-based alloy deposited on the outer surface of said core (16).

A process includes applying a slurry to a surface of a metallic article to produce a slurry film on the surface. The slurry is composed of a liquid carrier, chromium and aluminum, and an agent that is reactive with the chromium and aluminum to form intermediary compounds. The article and slurry film are then thermally treated at an activation temperature at which the agent reacts with the chromium and aluminum to form the intermediary compounds. The intermediary compounds deposit the chromium and aluminum on the surface. The thermal treating also diffuses the chromium and aluminum into a sub-surface region of the article such that the sub-surface region becomes enriched with chromium and aluminum.

A part include a refractory alloy including a niobium matrix having metal silicide inclusions present therein, the surface of the part being coated by a protective coating, the protective coating including a phase having the following stoichiometry: (Nb.sub.xTi.sub.1-x).sub.3M.sub.Cr.sub.Si.sub.X.sub. where M designates Fe, Co, or Ni, X designates one or more other elements that might be present, x lies in the range 0 to 1, x lies in the range 5 to 8.5, and the sum + lies in the range 3 to 7; or Nb.sub.4M.sub.Si.sub.X where M designates Fe, Co, or Ni, X designates one or more other elements that might be present, lies in the range 3.2 to 4.8, and lies in the range 6 to 8.

A method of coating a superalloy substrate, includes (a) aluminising the surface of the substrate to form an inner coating layer; (b) applying a slurry with a solid content including Cr, Al, Ni and Co onto the inner coating layer, where the Cr-content of the solid content is between 15% and 30% by weight thereof, and diffusion heat treating the slurry applied to the inner coating layer at a temperature above 800 C. for 1 to 8 hours to form an intermediate coating layer; and (c) applying a Cr-free slurry with a solid content including Al and Ni onto the intermediate coating layer, where the Al-content of the solid content is between 15% and 30% by weight of the solid content, and diffusion heat treating the slurry applied onto the intermediate surface layer at a temperature above 800 C. for 1 to 8 hours to form an outer coating layer.

A method of coating a superalloy substrate, includes (a) aluminising the surface of the substrate to form an inner coating layer; (b) applying a slurry with a solid content including Cr, Al, Ni and Co onto the inner coating layer, where the Cr-content of the solid content is between 15% and 30% by weight thereof, and diffusion heat treating the slurry applied to the inner coating layer at a temperature above 800 C. for 1 to 8 hours to form an intermediate coating layer; and (c) applying a Cr-free slurry with a solid content including Al and Ni onto the intermediate coating layer, where the Al-content of the solid content is between 15% and 30% by weight of the solid content, and diffusion heat treating the slurry applied onto the intermediate surface layer at a temperature above 800 C. for 1 to 8 hours to form an outer coating layer.

A method for manufacturing a part coated with a protective coating includes: forming a protective coating across all or part of the surface of a part, wherein the part includes a refractory alloy including a niobium matrix containing metal silicide inclusions, wherein the protective coating is formed by a pack carburization method from a cement including: i. a mixture A of (Nb.sub.xTi.sub.1-x).sub.3M.sub.3CrSi.sub.6 and M.sub.0.6Cr.sub.0.4Si where M denotes Fe, Co or Ni and x is between 0 and 1, or ii. a mixture B of MSi, NbSi.sub.2 and Nb.sub.4M.sub.4Si.sub.7 where M denotes Fe, Co or Ni.