Oxidation of nitride layers formed on Ti-6Al-4V alloys by gas nitriding

Abstract

Ti-6Al-4V alloys were nitrided through gas nitriding at 950°C for 3 h in deoxygenated, atmospheric nitrogen gas. During nitriding, nitrogen reacted and diffused into the alloys to form Ti2N and a meager amount of TiN in a Ti-N compound layer with a thickness of 20 µm to 25 µm. An α-Ti(N) diffusion layer with a thickness of 40 µm to 80 µm formed below this layer. A small amount of Al was dissolved at the top of the Ti-N compound layer because of the strong interaction of nitrogen with Ti and Al. Nitriding resulted in the dissolution of interstitial nitrogen and the formation of nitrides. Oxidation of the nitrided Ti-6Al-4V alloys initially resulted in the formation of a Ti-N-O layer, which later oxidized to TiO2. Above 800°C, the nitrided alloys oxidized rapidly, accompanied by microcracking of the TiO2 surface layer.

Isothermal oxidation kinetics of nitrided Ti-6Al-4V studied by infrared emissivity

“…Among them, gas nitriding has also been suggested as a potentially effective treatment against oxidation [14][15][16]. However, to our knowledge, only one qualitative study of the temperature-dependent oxidation kinetics of nitrided Ti-6Al-4V has been performed [17].…”

Mechanisms and Kinetics of Static Spheroidization of Hot-Worked Ti-6Al-2Sn-4Zr-2Mo-0.1Si with a Lamellar Microstructure

“…[19] The values of s BS predicted from Eq. [1] and [2] with the material data in Table I ( Figure 6, vertical lines) lie close to the end of the steep decrease in average AR.…”

“…TWO-phase (alpha/beta) titanium alloys are used widely in the aerospace industry because of their high specific strength, good corrosion resistance, and excellent high-temperature properties. [1,2] The most common method of producing semifinished titanium mill products comprises ingot melting and solidification followed by a series of hot-working and heat-treatment steps, each of which has a specific microstructural target. Usually, ingot breakdown is conducted above the beta transus temperature (at which alpha + beta fi beta) to produce a homogeneous, recrystallized beta-grain structure.…”

“…The solid vertical lines indicate the time required to complete boundary splitting estimated from Eqs [1]. and[2].…”

The Importance Of Surface Topography For The Biological Properties Of Nitrided Diffusion Layers Produced On Ti6Al4V Titanium Alloy

“…These features affect such functional properties as hardness, wear resistance, mechanical properties, biological properties and wettability. In order to modify the properties of biomaterials, different methods of surface treatment are used, ranging from electrochemical oxidation, thermal spraying, ion implantation, laser treatment (PLD), chemical vapour deposition (RFCVD, MWCVD), to hybrid and glow-discharge methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Selection of the appropriate method depends on the final application of the material, the implant's shape and the expected characteristics of the produced surface layers.…”