Research on Corrosion Resistance of Titanizing and Nitriding on Carbon Steel in H₂SO₄Solution

Abstract

Q195 steel was treated with titanizing followed plasma nitriding by glow plasma alloying technology using single pulse power supply. The corrosion resistances of titanizing sample and titanizing + ion nitrided sample were studied. The results show that the alloying layer is 200 μm in depth and organization is α-Fe solid solution containing Ti by plasma titanizing technology using single pulse power supply. An obvious reactive diffusion dividing line formed between alloying layer and the substrate. It shows that diffusion phenomenon happened in process of titanizing. The morphology of Ti alloy layer was columnar crystals. The content of Ti on the surface is up to 5 wt%. And the Ti content of alloying layer is in a decreasing from the surface to the inner on a gradient distribution. The phase structure of titanizing layer is composed of Fe2Ti, Fe-Ti and TiC phases. The phase structure of titanizing + ion nitrided sample was obviously TiN phase and a few Fe-Ti phase. The surface hardness of untreated carbon steel is 110 HV and that of the alloying layer of titanizing is 310HV. The surface hardness of titanizing + ion nitrided sample is 1800HV. The corrosion resistance of titanizing sample is increased 12.15 times compared with the untreated sample and 1.42 times compared with 18-8 stainless steel in H2SO4solution; The corrosion resistance of titanizing + ion nitrided sample is increased 7.444 times compared with the untreated sample and as well as 18-8 stainless steel in H2SO4solution.

Effects of Nitriding Subsequent Titanaliting of Steels

“…In the specialized literature there is information related to the association of chemical processes of titanating and nitriding [7] or nitriding and titanating [8,9], the association of the two manners of thermochemical processing aiming to ensure special performances to the superficial layers of metallic products: microhardness close to 2000 μHV or more, special tribological behavior, corrosion resistance in aggressive environments, and others such performances. All these performances seem to be ensured according to the conclusions of various experimental researches by the presence in the superficial layers of the metallic products processed in this way of titanium, aluminum nitrides, or complex titanium and aluminum nitrides.…”

“…[1,4]. According to the information of the specialized literature, the increase of the metallic products exploitation performances can be rendered by a succession of thermochemical processing as titanaliting followed by classical or plasma nitriding [7,8].…”

Nitriding in ammonia-nitrogen gaseous mixtures, after the simultaneous saturation with Ti and Al

“…in the surface areas of the layer, as they showed Kogan, 1976, 1982;Lahtin et al, 1991;Winter, 2009;Edenhofer et al, 2008) b By introducing in the general thermochemical processing flow of the products, prior to nitriding, some processing stages generating hardening phases, which later, during nitriding, by partial or total conversion into nitrides, to ensure an increase in the proportion of phases of interest in the areas surface of the layer. Achieving such a goal can be ensured by applying a titanisation or simultaneously saturation with Ti and Al, as they showed (Cojocaru et al, 2021;Bu et al, 2012;Ozkan and Saduman, 2012;Xua et al, 2020;Ghinea et al, 2020). Maintaining the tenacity of the central areas of thermochemically processed products, because titanisation or simultaneous saturation with Ti and Al is performed at temperatures higher then tempering, can be ensured by interposing a martensitic quenching in the neutral mediums or vacuum that preserve the composition of the phases, whether followed by high tempering, its effect being like the application of nitriding.…”