Recycling of Nickel-Containing Alloys

Nickel is rarely used by itself but is commonly mixed with other metals to produce alloys. This is very different from, for example, copper. There are thousands of different alloys containing nickel - each developed to offer a particular combination of technical properties (corrosion resistance, mechanical properties and service life) relevant to particular conditions of use.

The nickel content of these alloys varies widely from, as examples, 1-3% for special engineering steels, 8-14% for stainless steels, 15-40% for special engineering alloys, 40-90% nickel for special alloys for the aerospace and electronic industries.

It is usual practice for special alloys to be recycled as the same special alloy wherever possible: the stringent specifications and the cost of achieving them in the first place can justify them having their own closed loops: production of a specific, its use phase and then collecting and recycling that alloy material to produce “new” material that matches the original specification. The motivation is economic. If the identity of the alloy can be maintained from fabrication to end-of-life of the component, the alloy producer can use that scrap alloy to make new alloy components. This is economically and environmentally efficient as it allows the producer to achieve high quality product specifications without incurring extra refining or qualification costs. 

In practice it is not always possible to maintain and segregate products and scrap into specific alloys. Alloys and products get mixed. The nickel recycling industry has various ways of handling mixed nickel-containing scrap material in order to optimize the retained value of the scrap. One common technique is to melt the mixture in order to produce "remelt" ingot of a known composition for subsequent resale.

A variant of this is to adjust the composition of the remelted scrap by adding controlled amounts of primary metals in order to produce ingot to a required specification for resale. A further technique is to "blend" recycle material from different sources to produce a mixture which, when subsequently melted by the purchaser, will produce a melt with a specified composition. This blending process is of increasing importance in stainless steel production.