Diffusion surface alloyed metal exhaust component with welded edges
An exhaust component for a motor vehicle with improved corrosion resistance, including an internal volume, an inlet for receiving exhaust gas, and an outlet for expelling exhaust gas. The exhaust component includes at least one wall that is made of a diffusion surface alloyed metal sheet. The diffusion surface alloyed metal sheet comprises a secondary metal that is formed to a primary metal substrate by diffusion. A weld bead is applied to at least one of the edges of the diffusion surface alloyed metal sheet for edge protection or to join the edge of the diffusion surface alloyed metal sheet to another diffusion surface alloyed metal sheet. The weld bead includes a high chromium content filler metal to protect the weld bead and the primary metal substrate at the weld joint from corrosion.
1. An exhaust component for a motor vehicle, comprising:
an internal volume;
an inlet disposed in fluid communication with said internal volume for receiving exhaust gases;
an outlet disposed in fluid communication with said internal volume for expelling exhaust gases;
at least one wall made of a diffusion surface alloyed metal sheet comprising a secondary metal that is formed to a primary metal substrate by diffusion;
said diffusion surface alloyed metal sheet including at least one exposed edge that terminates in and is exposed to said internal volume or an external zone positioned outside said exhaust component; and
a weld bead extending along and covering said at least one exposed edge of said diffusion surface alloyed metal sheet such that said primary metal substrate at said at least one exposed edge of said diffusion surface alloyed metal sheet is protected from exposure to said internal volume or said external zone by said weld bead, wherein said primary metal substrate has a primary metal chromium content and said secondary metal has a secondary metal chromium content that is greater than said primary metal chromium content, wherein said weld bead is made of a filler metal that has a filler metal chromium content that is greater than said secondary metal chromium content.
2. The exhaust component set forth in claim 1 , wherein said diffusion surface alloyed metal sheet includes a core layer made of said primary metal substrate that is positioned between two cover layers made of said secondary metal.
3. The exhaust component set forth in claim 2 , wherein said diffusion surface alloyed metal sheet includes transition zones between said core layer and said cover layers where a molecular concentration of said secondary metal gradually decreases and a molecular concentration of said primary metal substrate gradually increases moving toward said core layer.
4. The exhaust component set forth in claim 2 , wherein said diffusion surface alloyed metal sheet includes transition zones between said core layer and said cover layers where a molecular concentration of chromium gradually decreases moving toward said core layer.
5. An exhaust component for a motor vehicle, comprising:
a housing including at least one outer wall defining an internal volume of said housing;
said at least one outer wall having an inside surface facing said internal volume of said housing and an outside surface facing an external zone positioned outside of said housing;
at least one inner wall positioned in said internal volume of said housing that defines an exhaust chamber within said internal volume;
at least part of one of said outer and inner walls being made of a diffusion surface alloyed metal sheet comprising a secondary metal that is formed to a primary metal substrate by diffusion;
said diffusion surface alloyed metal sheet including at least one exposed edge that terminates in and is exposed to said internal volume or said external zone; and
a weld bead extending along and covering said at least one exposed edge of said diffusion surface alloyed metal sheet such that said primary metal substrate at said at least one exposed edge of said diffusion surface alloyed metal sheet is protected from exposure to said internal volume or said external zone by said weld bead, wherein said primary metal substrate has a primary metal chromium content and said secondary metal has a secondary metal chromium content that is greater than said primary metal chromium content, wherein said weld bead is made of a filler metal that has a filler metal chromium content that is greater than said secondary metal chromium content.
6. The exhaust component set forth in claim 5 , wherein said diffusion surface alloyed metal sheet includes a core layer made of said primary metal substrate that is positioned between two cover layers made of said secondary metal.
7. The exhaust component set forth in claim 5 , wherein said filler metal chromium content is at least 20 percent chromium.
8. The exhaust component set forth in claim 6 , wherein said diffusion surface alloyed metal sheet includes transition zones between said core layer and said cover layers where a molecular concentration of said secondary metal gradually decreases and a molecular concentration of said primary metal substrate gradually increases moving toward said core layer.
9. An exhaust component for a motor vehicle, comprising:
an internal volume;
an inlet disposed in fluid communication with said internal volume for receiving exhaust gases;
an outlet disposed in fluid communication with said internal volume for expelling exhaust gases;
first and second walls joined together at a weld seam;
each of said first and second walls being made of a diffusion surface alloyed metal sheet comprising at least one cover layer of secondary metal that is formed to a core layer of primary metal substrate by diffusion;
said primary metal substrate in said core layers of said first and second walls having a primary metal chromium content;
said secondary metal in said cover layers of said first and second walls having a secondary metal chromium content that is greater than said primary metal chromium content; and
a weld bead positioned between said first and second walls that joins said first wall to said second wall at said weld seam, said weld bead containing a filler metal having a weld bead chromium content that is greater than said secondary metal chromium content of said cover layers in said first and second walls.
10. The exhaust component set forth in claim 9 , wherein said filler metal chromium content is at least 20 percent chromium.
11. The exhaust component set forth in claim 10 , wherein said primary metal in said core layers of said first and second walls is stainless steel and said primary metal chromium content of said core layers in said first and second walls is at least 10 percent chromium.
12. The exhaust component set forth in claim 9 , wherein said filler metal in said weld bead, said primary metal in said core layers, and said secondary metal in said cover layers are intermixed with one another at said weld joint and additively create said weld bead chromium content, which is within 3 percent of said secondary metal chromium content of said cover layers in said first and second walls.
13. The exhaust component set forth in claim 9 , wherein said first and second walls are spaced apart at said weld seam by a gap and said weld bead is positioned in and fills said gap between said first and second walls to join said first wall to said second wall at said weld seam.