Protective Ceramic Coatings on the Base of the Refractory Metals Carbides

Abstract

The aim of this work was obtaining of the protective coatings of the refractory metal carbides such as NbC, TaC, Cr7C3 on carbon steels and carbon fibers with further study their properties. The refractory metal carbides NbC, TaC, Cr7C3 were deposited on carbon steel and fibers by currentless transfer in molten salts at temperatures 1073-1123 K. The microhardness of refractory metal carbides on carbon steels at the cross section had the values 21 GPa, 29 GPa, 31 GPa for Cr7C3, NbC and TaC, respectively. The corrosion resistance of these carbides was studied in concentrated HCl, H2SO4 and H3PO4 acids at a room temperature during 48 hours. The corrosion tests were shown following rows of the chemical stability carbide coatings in HCl: Cr7C3>NbC>TaC; in H2SO4: TaC>Cr7C3>NbC; in H3PO4: Cr7C3>TaC>NbC. The wear resistance was evaluated by the mass loss of samples. The mass loss of a sample from a hardened St.3 was 35.2 mg cm-2 and that of a coated with a chromium carbide – 4.7 mg cm-2, niobium carbide – 2.9 mg cm-2 and tantalum carbide – 2.2 mg cm-2. Deposition of NbC coatings on parts of oil pumps increased their lifetime in several times. Coatings of Cr7C3 or TaC on the knifes for cutting rubber, made of St. 3, improve their wear resistance and increase a tool life in 2.0 – 2.5 times, respectively. Coatings of NbC or TaC on carbon fibers improve the mechanical resistance and they are compatible with fibers up to 1473 K in an aggressive atmosphere.