STRUCTURE OF A LAYER OF A HIGH-SPEED STEEL WITH NITROGEN DEPOSITED ON THE PARTS OF METALLURGICAL EQUIPMENT

10.25712/ASTU.1811-1416.2024.02.001

Abstract

The structure, microhardness and tribological properties of high-speed steel R18YU, alloyed with nitrogen and aluminum, aimed at rolls of medium-carbon steel 30HGSA, have been studied by methods of modern physical materials science. Plasma surfacing is carried out in a closed nitrogen medium with a powder wire. An adjustable thermal cycle was carried out to obtain a uniform state and prevent the formation of cold cracks. It was revealed that the deposited layer has a cellular-dendritic type structure. The grains are enriched with iron atoms, and the boundaries are separated by thin layers of the second phase enriched with atoms of chromium, aluminum, tungsten and vanadium. Needle-like inclusions with a length of 150-730 nm were found inside the central part of the grains. Four-fold high-temperature tempering at 580 °C for 1 hour provides: dissolution of nanoscale inclusions in the volume of grains; promotes a more uniform distribution of alloying elements; forms a lamellar (needle-like) type structure, characteristic morphologically for needle-like martensite. The assumption is put forward and justified that the grains of the deposited layer are formed by a solid solution of γ-iron (austenite). A slight decrease in microhardness, wear resistance and coefficient of friction of the surfacing layer after high-temperature tempering was revealed. This behavior of the surfacing material during high-temperature tempering may be due to the relaxation of thermal stresses formed in the layer during surfacing.