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 high-speed tool steel and CaF₂ solid lubricant. The composite is intended for operation at loads of 2.0–3.0 MPa and high rotation speeds (5,000–7,000 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’s metal matrix. In combination with CaF₂ solid lubricant, these strengthening phases impart high antifriction properties to the material under high-speed friction at speeds up to 7,000 rpm and loads of 2.0–3.0 MPa. Comparative tests of the new R2AM9K5 steel + (4.0−8.0)% CaF₂ composite demonstrated significant advantages in the antifriction properties over cast brass, currently used for units of modern rotary printing machines and can perform effectively only under continuous liquid lubrication. The R2AM9K5 steel waste composite containing CaF₂ solid lubricant permanently forms a protective antifriction 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. When the rotation speed increases up to 8,000 rpm, the composite antifriction properties decrease as the film on the contact surfaces becomes discontinuous. The research allowed operating limits to be determined for applying the new composite and proved the effectiveness of industrial grinding waste in developing high-quality structural materials through a reasoned choice of secondary raw materials, considering the nature of doping elements present in them.