Vibroacoustic diagnostics of surface electron beam alloying process of ferritic stainless steel

Abstract

Controlling the process of surface electron beam alloying substantially complicates the instability of the parameters of the microsecond pulse of the electron beam and the process of its interaction with the processed material, which leads to fairly significant random changes that occur spontaneously, regardless of the control system. In this situation, it is proposed to use the method of acoustic emission, which has long established itself as an effective tool in the study of phase transformations and plastic deformation. Under the action of a low-energy high-current electron beam, a vibroacoustic wave is caused by the effect of thermoelasticity in a thin surface layer heated up to the evaporation temperature of a substance in a vacuum. It is experimentally shown that a process with high vibroacoustic activity occurs upon irradiation of plates of pre-nitrided steel 08Cr17Ti with a deposited Nb70Hf22Ti8 film in the range 11-22 kHz after the 10th millisecond. The source of this vibroacoustic signal is the appearance of a martensitic component in the near-surface layer of the sample, caused by the formation of niobium-based nitride. Tracking changes in the effective value of the vibroacoustic signal allows us to select rational irradiation modes for electron-beam surface alloying, assuming, on the one hand, the maximum possible power supply, on the other hand, the limitations caused by the possibility of evaporation of the previously deposited film with the alloying components.