The efficiency of ion nitriding of austenitic stainless steel 304 using the “active screen”

The study examined layers were formed on the outer surface of austenitic stainless steel 304 under glow discharge conditions in the low-temperature and short-term ion nitriding. The outer layers analyzed in the work produced in parallel in the classical process of cathode and a novel method of “active screen”, intensifying the process of nitriding

The effectiveness of active screen method in ion nitriding grade 5 ELI titanium alloy

A titanium alloy for biomedical applications, Grade 5 ELI, was studied, which was subjected to the ion nitriding process in the temperature range of 530 – 590 °C and during 5 – 17 h, using two variants of sample arrangement in the glow discharge chamber. The first variant – the samples intended for nitriding were placed on the cathode, the second variant – the samples placed on the cathode were shielded with an active screen. In order to assess the effectiveness of nitriding, studies were carried out on the depth of nitrogen diffusion into the substrate of the studied titanium alloy, surface hardness tests, as well as observation of the obtained microstructures and phase composition tests – in order to assess the structure of the surface layers. It was found that using active screens increases the rate of nitrogen diffusion deep into the nitrided Grade 5 ELI titanium alloy, and thus increases the thickness of the obtained nitrided layers

A model for unconventional glow discharge nitriding of grade 2 titanium

An analysis of the influence of different parameters of the ion nitriding process conducted in a H2 + N2 atmosphere on the properties of the surface layer of Grade 2 titanium was carried out in the study. This allowed a model for ion nitriding of technical titanium to be developed. The equipment used in the experimental work included a JON-600 current glow-discharge furnace. It was found that the process of cathode nitriding with the use of the active screen led to an increase in the concentration of nitrogen in the surface layer and in the relative volume of nitrides. A factor which determines the qualitative and quantitative characteristics of phenomena that occur in the presence of the active screen is the high concentration and high energy level of nitrogen ions which interact with base material during nitriding

Ion nitriding using active screen method

Austenitic steel grade 304 according to AISI was tested after ion nitriding in the temperature range 325 - 400 °C and time range 2 - 4 h, and after two different variants of sample arrangement in a glow discharge chamber. The first variant – the samples intended for nitriding were placed on the cathode, the second variant – the samples placed on the cathode were shielded with an active screen. In order to evaluate the effectiveness of the nitriding process variants, investigations of the diffusion depth of the obtained surface layers, surface hardness tests and tribological wear tests were carried out. It was found that using active screens increases the rate of diffusion of nitrogen into nitrided austenitic steel 304, thus increasing the thickness of the resulting surface layers

Procjena učinka nitriranja plazmom titanovih legura za primjenu u medicini

The surface layers obtained on selected titanium alloys, used in medicine, by the nitriding under glow discharge condition were investigated. The results concern of: α- titanium alloy Grade 2 and α + β alloys Grade 5 and Grade 5 ELI nitrided in temperature below 873 K. The nitriding experiments were performed in a current glow-discharge furnace JON-600 with assisting of unconventional methods. After nitriding surface layers were characterised by surface microhardness measurements, chemical depth profiles, microhardness depth profiles and wear resistance tests.Istraživan je površinski sloj dobiven nitriranjem pri toplinskim postupcima odabranih titanovih legura, a koje se rabe u medicini. Rezultati se odnose na α-titanovu leguru 2. stupnja i α + β legure 5. stupnja i 5. stupnja ELI nitriranim na temperaturama ispod 873 K. Pokusi nitriranja su provedeni u prolaznoj toplinskoj peći JON-600 primjenom nekonvencijalnih metoda. Poslije nitriranja površinski slojevi su karakterizirani mjerenjem površinske tvrdoće, te po presjecima dubinski kemijski i mikrotvrdoće te otpor na trošenje

On Hausdorff dimension of the set of closed orbits for a cylindrical transformation

We deal with Besicovitch's problem of existence of discrete orbits for transitive cylindrical transformations $T_\varphi:(x,t)\mapsto(x+\alpha,t+\varphi(x))$ where $Tx=x+\alpha$ is an irrational rotation on the circle \T and \varphi:\T\to\R is continuous, i.e.\ we try to estimate how big can be the set D(\alpha,\varphi):=\{x\in\T:|\varphi^{(n)}(x)|\to+\infty\text{as}|n|\to+\infty\}. We show that for almost every $\alpha$ there exists $\varphi$ such that the Hausdorff dimension of $D(\alpha,\varphi)$ is at least $1/2$. We also provide a Diophantine condition on $\alpha$ that guarantees the existence of $\varphi$ such that the dimension of $D(\alpha,\varphi)$ is positive. Finally, for some multidimensional rotations $T$ on \T^d, $d\geq3$, we construct smooth $\varphi$ so that the Hausdorff dimension of $D(\alpha,\varphi)$ is positive.Comment: 32 pages, 1 figur

Procjena učinkovitosti nekonvencionalnog nitriranja austenitnog čelika 316L

The 316L grade austenitic steel after glow discharge nitriding at a temperature of T=733 K for a duration of τ = 61,2 ks and four different variants of specimen arrangement in the glow-discharge chamber was investigated. In order to assess the effectiveness of nitriding process variants, the profile analysis examination of obtained surface layers, surface hardness tests and surface layer hardness profile examination, the analysis of surface layer structures and abrasive wear were performed. It has been found that an application of the booster screens causes depth increase of the nitrogen diffusion into the nitrided 316L austenitic steel and thus an increase of the obtained surface layers thickness.Istraživani su uzorci austenitnog čelika stupnja 316L sa 4 različita postupka u komori za nitriranje na temperaturi T=733 K u trajanju τ =61,2 ks. Za procjenu učinkovitosti varijanti nitriranja provedena je analiza profila površinskog sloja, njegove tvrdoće kao i tvrdoće profila, površinske strukture te abrazijsko trošenje. Ustanovljeni su uzroci pojačane podrške i povećanje dubine difuzije u površini austenitnog čelika 316L pri nitriranju, te povećanje debljine nitriranog površinskog sloja