Abstract
The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 μm located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 μm in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life.
Highlights
One of the most widespread causes of equipment, mechanisms, machines and structures failure is fatigue fracture of parts
It is shown that different states of structure form in silumin surface layer depending on the parameters of electron-beam processing
In electron-beam processing according to the mode No 1 initiating the starting stage of silicon inclusions melting the formation of highly defective surface layer containing micropores and microcracks weakening the material are observed
Summary
One of the most widespread causes of equipment, mechanisms, machines and structures failure is fatigue fracture of parts In this connection, prevention of fatigue fracture of critical parts and, increase in their service life is an urgent problem [1]. Effective method of surface hardening of metals and alloys and, as a consequence, increase in fatigue service life is material’s surface processing with high-intensity electron beam of submillisecond duration. This method enables change in structure of tens micrometers thick surface layer by transforming it into multi-modal structure-phase state with practically unchanged structurephase state of the main volume of the alloy [3, 4]
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