Effective combined surface hardening processes of structural steels using ultrasound

Abstract

The effectiveness of hardening of the surface layer of machine parts is evaluated by the operational properties of the surface layer and depends on many conditions that characterize the specific features of the technological process in which this method of hardening is carried out. The surface plastic deformation of structural steels with the use of ultrasound is studied. Four variants of hardening are considered: ultrasonic treatment with continuous supply of ultrasonic energy, pulse ultrasonic treatment, combination of ultrasonic treatment with subsequent pulse treatment, ultrasonic treatment after hardening with induction heating. It is shown that ultrasonic treatment increases microhardness of surface layer of structural steels by 1.5 times, HF hardening by more than 2 times, HF hardening + UZO combination by 3 times and HF hardening + IUZO combination by 3.2 times. Ultrasonic treatment increases compression stresses occurring in steel surface hardened by HFI hardening. The compressive stresses increase especially strongly after pulse ultrasonic treatment with five passes and reach the value of 1200 Pa.