Functional Gradient Heat-Resistant Materials Manufactured by Spark Plasma Sintering

The objects of the study were powder samples PV-NiCr16Al6Y and PV-Ni75Al23W, intended for the formation of a sublayer in heat-shielding coatings. The aim of this work is to develop and study a sublayer with a complexly organized structure of a functionally graded material of the superalloy-sublayer-ceramic system for operation under thermal cyclic loads and high-temperature gas corrosion. Experimental samples of binding materials for heat-protective coatings (HPC) were obtained by the method of spark plasma sintering (SPS) at T = 1050 °C / 15-30 MPa / 5 min. Methods of laser diffraction, X-ray structural analysis, optical and scanning electron microscopy, X-ray fluorescence spectroscopy, microdurometry were used to study powders and consolidated materials. It is shown that irregular powders contain individual particles of some components - in PV-NiCr16Al6Y powder these are particles of chromium and yttrium, in PV-Ni75Al23W - tungsten and chromium. Consolidated sublayers of such powders exhibit inhomogeneity and irregular porosity. To solve the problem of forming a homogeneous binder sublayer, mechanical alloying of the powders before sintering is proposed. It was found that MA increases the homogeneity of the structure, excludes local inclusions of unreacted particles, and increases the activation of consolidation. MA and subsequent sintering opens up wide possibilities for controlling the structure, including the porosity of the sublayers, and specifying various options for the HPC architecture. Experimental samples of HPC on an Inconel 625 substrate with a mechanically activated PV-Ni75Al23W sublayer and dioxides Zr/Y (YSZ) outer ceramics were obtained by the SPS method. A model of the architecture of a HPC made of a layered binder with different porosities is proposed.