INCREASING THE SERVICE LIFE OF CENTRIFUGAL COMPRESSORS BY ELECTROEROSION ALLOYING OF IMPELLERS

摘要

The reliability and durability of centrifugal compressors and similar machines (blowers) are determined by the quality of the parts, the serviceability of which depends mainly on the quality of their surface layer. The impeller has the highest load of any element in the flow section of a centrifugal compressor. When the impeller rotates at high speed (the circumferential velocities reach 300 m/sec), the centrifugal forces in the impeller material cause high internal stresses. Moreover, the impeller is subjected to the action of pressure, temperature, and a corrosive working medium. Carbon steels are used for impellers if a noncorrosive gas is the working medium and alloy and chromium-nickel steels (30KhGS, Kh15NYuA, 07Kh16N6, etc.) are used for work with corrosive working media. Impellers can be divided into three technological groups: 1. open design: all the elements of the impeller (main disk, covering disk, and blades) and are then put together by riveting, welding, or brazing; impeller is assembled. 2. half-open design: entirely milled (blade) and covering disks are made and then put together by riveting, welding, or brazing; impeller is assembled. 3. closed design: monolithic impeller; made by casting, milling, electroerosion machining. The manufacture of impellers in the various groups differs as to technological processes, equipment used, and appliances. Such a classification makes it possible, despite the diversity of impellers, to develop typical technological processes for strengthening them and thus speed up their manufacture. The complexity and high cost of producing centrifugal compressor impellers lead to exacting wear resistance requirements.