Quantitative evaluation of machined and laserhardened surfaces by x-ray and micromagnetic techniques

Machining of components like grinding, turning, shot peening, work hardening, diamond burnishing and power brush finishing as well as thermal treatments such as laser-, induction- and case hardening or nitriding change the microstructure and the residual stress state in surface layers up to approximately one millimeter of depth. Nondestructive techniques have the ability to characterize microstructure and residual stress in these layered structures and because of the numerous rather complex interactions with the material, multiparametrical strategies are applied. Using at least two, in major applications up to eight parameters derived from different micromagnetic quantities like Barkhausen noise, incremental permeability and tangential field strenght, satisfying results have been achieved. Investigations using mechanically machined components as well as those with laserhardened surfaces are performed. The results like the quantitative evaluation of the stress states, of the hardness va lues and of the depth of the hardened layers agree well with the results of x-ray and other conventional tests. In order to meet the requirements of applications under workshop conditions, a portable system (3MA-PC) has been developed. Handy multiparameter probes are available to meet different geometrical conditions. Data acquisition and evaluation is supported by a PC with Window-surface to facilitate the application.