A steel member with surface modified during manufacture has good anti-corrosion properties. The steel member includes a steel substrate, a metallic diffusion layer formed on the steel substrate, and an alloy deposition layer formed on the metallic diffusion layer. The steel substrate is made of low-carbon steel or low-carbon alloy steel. After cleaning and heating processes are applied, the metallic diffusion layer includes pearlite and ferrite crystals and hardness of the surface is also enhanced. The alloy deposition layer includes zinc ferrum alloy.

A steel member with surface modified during manufacture has good anti-corrosion properties. The steel member includes a steel substrate, a metallic diffusion layer formed on the steel substrate, and an alloy deposition layer formed on the metallic diffusion layer. The steel substrate is made of low-carbon steel or low-carbon alloy steel. After cleaning and heating processes are applied, the metallic diffusion layer includes pearlite and ferrite crystals and hardness of the surface is also enhanced. The alloy deposition layer includes zinc ferrum alloy.

A method for producing a porous member, whereby a member having smaller microgaps can be produced, and additionally, the outermost surface alone can be made porous and a porous layer can be formed on the surface while maintaining the characteristics of portions in which no porous layer is formed, is provided.

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 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.

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.