A landscape of melted Nickel

When heat-treating metal objects, it’s common to wrap them in a metal foil. This prevents the steel from building up excessive surface scale by excluding atmospheric gasses. In this case, 316 stainless steel was heat treated while wrapped in Nickel foil. Usually that works pretty well, but this time around the furnace temperature ran a bit high. As a result, the Nickel foil partially melted and fused to the steel. The result has quite an unusual look!

The partial melting of the Nickel results in what I think is an incredible visual effect. Molten Nickel readily wets the substrate steel, resulting in undulating and flowing patterns. Under 4x magnification the resemblance to a landscape, as shot from the air, is striking.

The gold to purple/blue coloration is caused by and effect known as thin film interference. This is the same phenomenon that causes the distinctive coloration of soap bubbles and oil films on water. In this case, a thin clear coating (probably Nickel oxide) has formed on top of the foil. Different colors indicate areas of differing film thickness - which in turn reflect variations of temperature within the furnace.

In the end, this was a failure caused by poor process control. But at least it yielded something interesting to look at!