The Surface Hardening of Parts of Liquid Dampers Made of High-Strength Steels

Variants of air-plasma sputtering (APS) and supersonic gas-flame sputtering in the HVOF modification of wear-resistant coatings on 30HGSN2A steel, used for the manufacture of rods of liquid dampers, have been worked out. Powder mixture designated as mixture A with chemical composition (wt%): 85 % chromium carbide (Cr3C2) powder and 15 % steel powder consisting of 20 % chromium and 80 % nickel were used for spraying. During the quality control of the applied coatings were evaluated: appearance, thickness, adhesion strength, microhardness and porosity. The phase composition of the coatings was also determined. The deposition modes are determined for varying the size and shape of powder mixture particles, as well as the deposition distances, which allow obtaining coatings with the required values of microhardness, adhesion strength and porosity. Such coatings can be obtained by using each of the three powder mixtures studied. The highest microhardness of the coating (11500-12100 MPa) was achieved using the powder mixture C (86%WC + 10%Co + 4%Cr) – and the HVOF method. The phase composition of this coating is represented by WC (base) and W2C carbides. The maximum shear strength (114 MPa) was achieved using a powder mixture A (85% Cr3 C2 + 15%X20H80) and the APS method. In the first variant, the porosity of the coating is 1.8-2.0 %, in the second - 5-8 %.