The Research Of Fe-based Graphite Style Self-lubrication Bead Welding Coating

Friction and wear are the main factors for materials and energy loss. Lubrication is the most effective method to reduce friction and wear. Self-lubricating materials, with excellent friction wear resistance quality, is one of the hot areas in materials research. In this study, traditional electrode build up welding method is used to generate self-lubricating graphite phase by in situ synthesis method. The effects of different alloying elements (Si, Ni, Al) in the graphite morphology on the strength, toughness and friction wear resistance of welding beam is systematically studied. Results indicate that the in-situ synthesis of graphite phase were evenly distributed, surface out of coating was thick. So this is a kind of low-cost ideal self-lubricating coating material.Study on the formulation of the surfacing material indicated that: SiC is the carbide that provides graphite. After thermodynamic calculation, graphite is theoretically to be formed. Graphite was not formed when the weight factor of SiC coating is below 10%; but when the weight factor is between 20% and 50%, Graphite was formed. When the weight factor of SiC coating is 20%, the electrode weldability is the best. Ni,Al and B can reduce the surface tension of the droplet. The co-effect of Al and Ni can significantly increase the surface tension of the droplet. Excessive cooling speed of weld beam counted against the precipitation of graphite. There are two factors affecting the formation of weld beam: One is the added amount of the graphite element Al, and the other is the the content of carbon in the welding beam. Graphite is formed by eutectic reaction when the welding metal is in the liquid form.The carbon content is an important factor for whether the graphite can be precipitated or not. Elements Si and Al are to promote formation of flake graphite, but element B and Ni are to promote the formation of spherical graphite. Graphite is gradiently distributed in the weld metal. The toughness of the welding beam is poor Because of the welding defects.Study on the graphite self-lubricating coating friction and wear properties shows that: the friction coefficient has little discrepancy when 20SiC in heavy load and low load, and a little larger in heavy load. The trends of friction coefficient curves are the same. Under heavy load, the wear form is fatigue wear; and under low load, the wear form is cutting wear. The friction coefficient is not stable in the initial period of friction. When friction goes into the balance, the friction coefficient tends to be identical. If the hardness of the two friction pairs is little different from each other, the peak roughness of the two friction pairs is worn by each other. Then wear is maintained at a low level. With the wear and tear becomes into a stable state, graphite forms a stable lubricating film to reduce wear and tear. Anti-vice versa.