Effect of aging at 750℃ on microstructure and mechanical properties of a new type of silicon biphase wear-resistant plate
Since the first discovery of biphase structure in 1927, biphase wear-resistant plates have been rapidly developed. The structure of biphase wear-resistant plate is composed of two phases of ferrite and austenite. It has the advantages of ferrite wear-resistant plate and austenite wear-resistant plate, and has excellent mechanical and wear-resistant properties. Wear-resistant plates are widely used in mining, cement, engineering, energy and other fields.
At present, designs a new type Si bipolar plate materials wear-resisting 00 cr20ni6si3 Cr20 department. 5 cu1. 5 mo1. 3 n0. 2 (mass fraction, %). Pure iron, pure chromium, pure nickel, ferrosilicon, pure copper and ferro molybdenum alloys were melted and cast into ingot by ZG-25 vacuum medium frequency induction furnace under the protection of argon. The measured chemical composition of the alloy (mass fraction, %) : C0.032, N0.124, Cr19.9, Ni5.89, Si3.44, Mo1.26, Fe margin.
After peeling and hot forging, the ingot was sampled along the hot forging direction. After solid solution at 1050℃ for 30min, the sample was aged at 750℃ for 0.5, 1.5, 3, 6, 10h and 15h, and then water quenched. The sample was ground and polished, then cleaned and dried with alcohol and acetone, and electrolytically etched in 10% KOH solution for about 30s. The microstructure of the sample was observed by metallographic microscope (OM) and scanning electron microscope (SEM). The characteristics of precipitated phase after aging treatment were observed by JEM2010F transmission electron microscopy (TEM). According to the national standard GB/T229-2007, the material after solution and aging treatment was processed into 10mm×10mm×55mmV notched impact sample along the forging state direction. The impact test was carried out with AHC-3000/2-AT impact testing machine at room temperature. The maximum impact energy was 300J, three effective samples were tested for each test condition, and the average value of the impact absorption energy was taken. The impact fracture morphology was observed by scanning electron microscope. The hardness of the sample after solution and aging treatment was measured by Brinell hardness tester. The results show that:
(1) The aging treatment significantly reduces the impact performance at room temperature, and the impact energy absorbed at room temperature drops sharply from about 150J of the solid solution sample to less than 20J of the aging sample. The Brinell hardness of the solid solution sample is about 252HB, and the Brinell hardness increases slightly to about 271HB after aging for 1.5h. The Brinell hardness of the samples with aging time longer than 1.5h has little change, and all of them are between 240 and 247HB.
(2) With the increase of aging time, the average size of rod-shaped ε-Cu phase increases slightly, and the Cu content in ε-Cu phase increases. After a short aging time, the precipitation of nanometer ε-Cu phase in austenite and the precipitation of finer granular Cr23C6 carbide at the ferritic/austenite phase boundary can improve the Brinell hardness of Cr20 biphase wear-resistant plate. The amount of Si3N4 phase precipitated increases with the aging time, and the precipitation of Si3N4 phase in the ferrite phase and the ferrite/austenite phase boundary significantly reduces the impact performance of Cr20 biphase wear-resistant plate at room temperature.
