Materials, methods and techniques for surface alloying sand casted articles

An article, comprising:

• a surface alloyed layer formed through controlled melting and solidification of metal and ferro-alloy powders, the surface alloyed layer comprising:
• 5 to 15 weight percent (wt %) nickel (Ni),
• 5 to 30 wt % chromium (Cr),
• 0.1 to 5 wt % molybdenum (Mo),
• optionally manganese (Mn) and/or silicon (Si),
• and balance iron (Fe),
• wherein the surface alloyed layer has a thickness ranging from 10 μm to 5,000 μm and exhibits a dendritic microstructure enriched with nickel (Ni), chromium (Cr), and at least one of:
• molybdenum (Mo), manganese (Mn), and silicon (Si), which are distributed in the surface alloyed layer;
• a steel base metal;
• and
• a transitional layer integrally formed between the surface alloyed layer and the steel base metal, the transitional layer comprising a gradual composition gradient of chromium (Cr), nickel (Ni), iron (Fe), molybdenum (Mo), manganese (Mn), silicon (Si), or iron (Fe),
• wherein formation of the transitional layer provides the gradual composition gradient which would lead to bonding of the surface alloyed layer to the steel base metal and prevent flaking during thermal cycling;
• and
• wherein the article is produced using a method that includes:
• preparing a slurry comprising metal and ferro-alloy powders with defined particle size ranging from 200-2000 μm;
• pouring molten steel base metal at a temperature sufficient to melt the metal and ferro-alloy powders in a range of 1650-1800° C. and form a mixture with the steel base metal;
• solidifying to form the surface alloyed layer with the dendritic microstructure;
• and
• performing one or more post-casting heat treatments selected from normalizing, tempering, and solution.