Investigation of the Formation of Structure and Properties in a Billet Made of Heat-Resistant Nickel Alloy EP741NP, Obtained by Hot Isostatic Pressing Technology

Abstract

It is known that the technology of hot isostatic pressing (HIP) can reduce the residual porosity and increase the level of physical and mechanical characteristics of products obtained by powder metallurgy methods. In modern aircraft and rocket engineering, heat-resistant heterophase nickel alloys are used, which are obtained with the use of granular metallurgy. This material is indispensable in the creation of disks of gas turbine engines (GTE), which are part of the turbine rotor and serve to install the blades. Obtaining a nonporous product made of EP741NP alloy using the HIP technology will increase the service life of the turbine disks, which is an urgent task at the present time. The aim of the work is to study the structure and physical and mechanical properties of a billet made of heat-resistant nickel alloy EP741NP obtained by the HIP method at a temperature of 1150 °C. The starting material for the preparation of the workpiece is a metal powder EP741NP, obtained by gas atomization and having a fractional composition of 20...50 microns. It is shown that the HIP process at a temperature of 1150 °C makes it possible to obtain an optimal combination of physical and mechanical properties. Based on the obtained images of powder particles and the microstructure of the work piece, the shape of the particles of the powder under study, the main category of powder granularity was determined and digital porosity analysis of the workpiece under study was performed in the Thixomet Pro software package. The changes in density and hardness along the section of the work piece were also evaluated. It has been established that at a temperature of HIP 1150 °, the average porosity is insignificant and is 0.1 %, however, as we move away from the edge of the workpiece to its center, there is an increase in the content of pores, the size of which lies in the range of 1...20 microns. It is shown that during the technological process of HIP, an arched effect is observed, the consequence of which are overestimated characteristics of microhardness and density at the edge of the work piece.