Structure and Corrosion Resistance of TiN Layer Synthesized by Plasma Surface Alloying Technology

A new technique of TiN layer forming on the carbon steel surface by the double glow-discharge plasma surface alloying technique was introduced. The microstructure, component concentration, hardness, phase analysis and corrosion resistance of the TiN layer were tested. The results show that TiN layer was a gradient structure, which compose of external deposition layer and diffusion layer with evenly distributed TiN particles. The layer thickness is 16 m, and a metallurgical bonded layer is obtained between the layer and the matrix. So TiN layer bond well with the matrix. Its surface morphology is cell shape, the golden yellow TiN grains are compact and uniform. In the TiN layer, the atom ratio of Ti/N is close to 1:1, and the surface micro-hardness is about 3120 HV, the preferred orientation of TiN layer is crystal surface (111). In 3.5% NaCl solution, its corrosion resistance was increased almost 11.3 times compared with untreated Q235 steel, but a little lower than 1Crl8Ni9Ti stainless steel. In l mol/L H₂SO₄ solution, the corrosion resistance of TiN layer was increased 11.5 times compared with untreated Q235 steel and 2.65 times compared with 1Crl8Ni9Ti stainless steel. Compared with its corrosion resistance in NaCl solution, the corrosion resistance of TiN layer was better in H₂SO₄ solution. In 4% NaOH solution, the corrosion resistance of TiN layer was increased 27.8 times compared with untreated Q235 steel and close to 1Cr18Ni9Ti stainless steel.