1. Different sources of part contamination

1.1 Contaminants and interaction with heat treatment

Chemicals are used at every stage in the manufacture of parts, to enable or facilitate their processing. However, these same products may prove harmful at a later stage in the manufacturing process. This is known as contamination. During heat treatment, contaminants present on parts after degreasing break down. The presence of these contaminants or decomposition products, due to the interaction between the chemical product (and/or a treatment gas) and the parts to be treated or the furnace elements, can lead to a change in mechanical properties or physical-chemical characteristics at high temperatures.

The main problems encountered include :

• treatment heterogeneity...