by George Langford, Sc.D., Massachusetts Institute of Technology, Cambridge, MA, 1966
Copyright©2005 by George Langford
Surface Coatings and Heat Resisting Alloys - Lesson 3 - Eighth specimen
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This series of
images shows an unsuccessful attempt to coat a low carbon steel with a
heat resistant alloy by welding.
All three photomicrographs are at 100X original magnification. |
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This photomicrograph shows that there is no zone of
intermixing between the low carbon steel at left and the heat
resistant alloy at right. I gave up trying to correct the color balance of this image, so it is presented in greyscale to preserve a degree of contrast between the two microstructures. |
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This is the steel substrate, in color this time. |
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The cast microstructure of the heat resistant alloy, shown
in color at left, has two phases. It is called Stellite and is
based on cobalt plus 30% copper, 10% tungsten, 1% carbon, and 1% iron. The coating, even though its microstructure is sound, would probably spall off the steel in service due to the lack of any metallurgical bonding between the coating and the substrate. |
| Specimen 9 shows a better coating process. |