Process diagrams for laser transformation hardening

Analytical mathematical models are applied to laser transformation hardening of engineering steels. The depth and maximum hardness of the transformed region are modelled in terms of the principal process variables. Dimensionless groups comprising material and processing variables are identified, and relationships with the properties of the transformed region are established. Good agreement between experimental results and model predictions is obtained. Data are presented in the form of various process diagrams. In their most practical form, these can be used to select the laser power and traverse rate required for hardening a particular material to a given depth with a fixed beam geometry. Alternatively, when constructed using dimensionless groups, the diagrams provide a means of displaying data for a range of materials, and evaluating the effects of variations in all the process variables on the properties of the transformed region. Thus process variables may be optimised with respect to various productivity criteria, and an estimate made of the sensitivity of the process to variations in process variables. The models can be used in a variety of ways: to expedite the trial and error testing phase of procedure development; as the core of an on-line adaptive control system; and as an educational tool.