Peculiarities of hardening of steel – copper alloy pseudo-alloys obtained by infiltration during hot plastic deformation

Abstract

The influence of the regimes of plastic deformation of steel – copper alloy pseudo-alloys obtained by infiltration on their structure, mechanical properties and anisotropy of properties is investigated. It has been established that hot forging of pseudo-alloys at a temperature of 700–950 °C provides an increase in strength by 1.5–3 times, impact strength by 1.5–2.5 times, plasticity by 1.5–2 %, and at 1100–1150 °С (above the melting point of copper) – leads to cracking of the material. It is shown that the properties of pseudo-alloys based on steel alloyed with chromium are lower than those based on steel alloyed with nickel, which is associated with the formation of chromium oxides due to its increased affinity for oxygen. The formation of macro-texture in pseudo-alloys after hot stamping has been established, which leads to secondary anisotropy of properties, the level of which is determined by the degree of deformation and temperature, but does not exceed 15–20 %. The deformation curve of the pseudo-alloy during hot forging was constructed, which revealed the optimum temperature (700–900 °С) and the limiting degree of deformation (65 %) depending on the composition of the pseudo-alloy. With an increase in the degree of deformation, microcracks form at the interface between the iron and copper phases, which in turn leads to a decrease in strength, ductility, as well as a 1.5–2-fold decrease in the impact strength of pseudo-alloys with a copper phase content of 15 % and destruction of pseudo-alloys with a 25 % copper content phases, in which the length of interphase iron-copper boundaries is much greater. The achieved mechanical properties of hot-forged steel-copper alloy pseudo-alloys make it possible to use them for parts of heavily loaded friction units, as well as parts for structural purposes.