Microstructure and Dry Sliding Wear Behavior of Fe-Based (Cr, Fe)_7C_3 Composite Coating Fabricated by PTA Welding Process

摘要

Using Cr_3C_2 and Fe-CrNiBSi powder blends as raw materials, an α-Fe matrix composite coating reinforced by in situ (Cr, Fe)_7C_3 rods, with a thickness of about 3.6 mm, was fabricated on the surface of AISI A36 low carbon steel by means of plasma-transferred arc welding. The results of microstructural analysis show that in the coating, a large number of carbides, (Cr, Fe)_7C_3, in rod shape grow, and radiate around some half-dissolved Cr_3C_2 particles. The results of dry sliding wear tests at loads 100, 200, and 300 N show that the wear resistances of (Cr, Fe)_7C_3-reinforced coating, respectively, are about 6.9, 14.9, and 17 times higher than that of nonreinforced pure Fe-CrNiBSi alloy coating; the average value and fluctuation range of friction coefficient (FC) of (Cr, Fe)_7C_3-reinforced coating are less than those of pure Fe-CrNiBSi alloy coating; the main wear mechanisms of pure Fe-CrNiBSi alloy coating are ploughing, deformation, and adhesive wear, whereas those of (Cr, Fe)_7C_3-reinforced coating are microcutting, abrasive, and oxidation wear; the cracks on surfaces of (Cr, Fe)_7C_3 rods increased with the increasing loads; and the matrix α-Fe can prevent them from extending further in the composite coating.