5. Dimensional stability of steels after quenching and tempering

The geometry of the components of high-precision mechanical equipment is defined with tolerances that are sometimes very narrow, and within which the dimensions of the parts must lie. However, in order to ensure satisfactory use and to allow the use of spare parts, it is essential that these dimensional imperatives are maintained over time. To meet these conditions, the various components, as well as the reference elements used during metrology operations, must have excellent dimensional stability over time. This is a function of load conditions, which can lead to plastic deformation, but above all of metallurgical factors likely to modify the mass volume of the metal, i.e. structural transformations. The various parts used generally undergo a heat treatment involving quenching followed by tempering at varying temperatures. The resulting structures consist of tempered martensite, more or...