WEAR-RESISTANT COMPOSITES PRODUCED  FROM TOOL STEEL WASTE FOR CONTACT JOINTS OF HIGH-SPEED PRINTING MACHINES 

Abstract

The paper examines the effect of doping elements on the structurization and properties of a new antifriction composite produced from grinding waste of the R2AM9K5 tool high-speed steel with solid lubricant CaF₂. The composite is intended for operation at loads of 2.0–3.0 MPa and high rotation speeds (5000–7000 rpm) in contact joints of high-speed printing machines. The production process imparted a heterophase structure to the antifriction composite. The composite consists of a metal pearlite–carbide and carbonitride matrix and CaF₂ solid lubricant particles being evenly distributed in it. Valuable Mo, Cr, W, V, N, and Co doping elements contained in the R2AM9K5 steel waste particles promote the formation of strengthening phases in the composite metal matrix. In combination with the CaF₂ solid lubricant, these strengthening phases impart high antifriction properties to the material under high-speed friction at speeds up to 7000 rpm and loads of 2.0–3.0 MPa. Comparative tests of the new composite produced from grinding waste of the R2AM9K5 steel + (4.0−8.0)% CaF₂ demonstrated significant advantages in the antifriction properties over cast brass, which is currently used for units of modern rotary printing machines and can perform effectively only under continuous lubrication with liquid oil. The studied composite produced from the R2AM9K5 steel waste, containing the CaF₂ solid lubricant, permanently forms an antifriction protective separating film on the contact surfaces in the friction process, which was confirmed by electron microscopy studies. Under these friction conditions, the film is continuous, uniform, and smooth and is constantly restored on its worn areas, leading to self-lubrication mode. When the rotation speed increases up to 8000 rpm, the composite antifriction properties decrease as a discontinuous film forms on the contact surfaces. The studies allowed the operating limits to be determined for the application of the developed composite and proved the effectiveness of using industrial grinding waste to develop new high-quality materials for structural purposes through a rational choice of secondary raw materials, considering the nature of doping elements present in them.