Study On The Compositions, Microstructures And Properties Of The Hi-Chromium Alloy Furnace Used In Grate Bar

This paper studied on the oxidation resistance properties, mechanics properties and high-temperature abrasive wear properties of the grate bar at different compositions through orthogonal experiment. Protracted the kinetic oxidation curve and calculate the oxidation velocity, then observed the oxidation film microstructures through SEM, analyses the phase of the oxidation film in XRD and EDS. Observed the cast microstructures through SEM and optics microscope and compare the microstructures of the alloy after oxidation. Discuss the differences between high temperature abrasive and room temperature abrasive.The results were shown that the primary factor to the oxidation and toughness is Al. C is the primary factor to hardness. The kinetic oxidation curves were regarded as parabola after 900℃and 500 hours oxidation, As carbon and chromium content increased, the oxidation film became friable and part desquamated, the kinetic oxidation curve emergence inflexion, after adding rare earth element in alloy, oxidation film desquamate rare emergence. The oxidation film of the Alloy without Al is black, after adding Al element, the oxidation became silvery. In the experiment, the matrix of the alloy is ferrite, the carbide is M₂₃C₆, as the carbon increase, the carbide increase. Owing to adding rare earth, the reticulation carbide became isolated, during oxidation process, the carbide dissolved in and separate out of the matrix, then detached from the necking, the carbide became more separated and the sharp carbide became blunt, compare to the harder alloy with some M7C3 in room temperature, the softer alloy had high wear rate, but at high temperature, the wear rate less than the harder alloy. This is because the matrix became soft at high temperature, which can not afford enough sustentation.Through analyzing the out coming and the microstructure, we can find that the most optimize composition of the Furnace grate bar content carbon was 1.2%, chromium was 26%, aluminium was 4%, silicon was 2%, rare earth element was 0.3%.