Abstract
The article studies new heat-resistant and wear resistant materials for operation under extreme conditions, especially in the power industry. The methods that improve the quality of a metal in metal castings through the influence of alloying elements on its structure and properties have been considered. These methods are very effective for reducing the tendency of a metal to form a coarse–grained structure. The paper describes optimal techniques for melting special alloys in induction and electric furnaces. A set of rules for the selection of a melting temperature before pouring a metal into the casting forms depending on the dimensions, wall thickness, geometry of castings have been determined. The behavior of new alloys under the conditions of high temperatures, aggressive environments has been studied. It has been established that heat–resistant Cr–Al steels exhibit high heat resistance and wear resistance properties; they 6–8 times surpass Cr–Ni steels in oxidation resistance. The proposed Cr–Mn cast iron processed in an integrated manner with REM (rare earth metals) and Ti is superior to a basic cast iron in conditions of a heavy wear. Numerous industrial trials confirm the usefulness of recommended new casting materials for use under extreme conditions.
Highlights
High and low temperatures, aggressive environments, intensive abrasive, impact-abrasive and hydro-abrasive wears and other factors are considered as extreme conditions for the operation of metal goods
Fe-based heat-resistant alloys like Cr, Cr-Ni and Cr-Al steels are classified as the materials operating in the conditions of high temperatures and aggressive environments [1, 2]
The effect of Cr and Al on casting properties of heat-resistant alloys Technological properties of heat-resistant steels are determined by content of main elements – Cr and Al [9]
Summary
High (up to 1350 °C) and low (to –190 °C) temperatures, aggressive environments, intensive abrasive, impact-abrasive and hydro-abrasive wears and other factors are considered as extreme conditions for the operation of metal goods. Fe-based heat-resistant alloys like Cr, Cr-Ni and Cr-Al steels are classified as the materials operating in the conditions of high temperatures and aggressive environments [1, 2]. The analysis of operating conditions of such details has defined that heat-resistant alloys, recently being used for their manufacture, have significant drawbacks: their structure includes expensive and scarce elements (nickel, cobalt, molybdenum and others) They are low-tech as a casting material (containing small percentage of carbon – up to 0.1 %) and have limited perfor-. The study of wear resistance of the cast iron was carried out on a special appliance, which models real operation conditions of details in a hydro-abrasive environment (a mixture of quartz pit sand and water) by means of rotating samples 65×25×10 mm in size. The cross section of these samples corresponds to the average cross section of the walls of details of ash pumps
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