• Journal of the Korean institute of surface engineering
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• v.51 no.4
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• pp.249-255
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• 2018

High temperature and low temperature gaseous nitriding was performed in order to study of the surface hardening and wear properties of the nitrided AISI 410 Martensitic stainless steels. High temperature gaseous nitiridng (HTGN) was carried out using partial pressure $N_2$ gas at $1,100^{\circ}C$ for 10 hour, and Low temperature gaseous nitiridng (LTGN) was conducted in a gas mixture of NH3 and N2 at $470^{\circ}C$ for 10 hour. The nitrided samples were characterized by microhardness measurements, optical microscopy and scanning electron microscopy. The phases were identified by X-ray diffraction and nitrogen concentration was analyzed by GD-OES. The HTGN specimen had a surface hardness of about $700HV_{0.1}$, $350{\mu}m$ of case depth. A ${\sim}50{\mu}m$ thick, $1,250HV_{0.1}$ hard nitrided case formed at the surface of the AISI 410 steel by LTGN, composed nitrogen supersaturated expanded martensite and ${\varepsilon}-Fe_{24}N_{10}$ iron nitrides. Additionally, the results of the wear tests, carried out LTGN specimen was low friction coefficient and high worn mass loss of ball. The increase in wear resistance can be mainly attributed to the increase in hardness and to the lattice distortion caused by higher nitrogen concentration.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.1
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• pp.19-27
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• 1983

This paper deals with hardness and wear characteristics of ion-nitrided metal, and with ion-nitride processing which is concerned with the effects of added carbon content in gas atmosphere. A small optimal amount of carbon content in gas atmosphere increase compound layer thickness, as well as to increase diffusion layer thickness and hardness, and reduces wear rate when the applied wear load is small. It is found in the analysis that under small applied wear load, the critical depth where voids and cracks may be created and propagated is located at the compound layer, so that the abrasive wear where hardness is an important factor, is created and the existence of compound layer reduces the amount of wear. When the load becomes large, the critical depth is located below nucleation and propagation, is created and the existence of compound layer increase wear rate.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.716-721
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• 2009

The major drive for the application of low-temperature plasma treatment in nitrocarburizing of austenitic stainless steels lies in improved surface hardness without degraded corrosion resistance. The low-temperature plasma nitrocarburizing was performed in a gas mixture of $N_{2}$, $H_{2}$, and carbon-containing gas such as $CH_{4}$ at $450^{\circ}C$. The influence of the processing time (5~30 h) and $N_{2}$ gas composition (15~35%) on the surface properties of the nitrocarburized layer was investigated. The resultant nitrocarburized layer was a dual-layer structure, which was comprised of a N-enriched layer (${\gamma}_N$) with a high nitrogen content on top of a C-enriched layer (${\gamma}_C$) with a high carbon content, leading to a significant increase in surface hardness. The surface hardness reached up to about $1050HV_{0.01}$, which is about 4 times higher than that of the untreated sample ($250HV_{0.01}$). The thickness of the hardened layer increased with increasing treatment time and $N_{2}$ gas level in the atmosphere and reached up to about $25{\mu}m$. In addition, the corrosion resistance of the treated samples without containing $Cr_{2}N$ precipitates was enhanced than that of the untreated samples due to a high concentration of N on the surface. However, longer treatment time (25% $N_{2}$, 30 h) and higher $N_{2}$ gas composition (35% $N_{2}$, 20 h) resulted in the formation of $Cr_{2}N$ precipitates in the N-enriched layer, which caused the degradation of corrosion resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1047-1053
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• 2016

In this study, welding of pure titanium was carried out by using a continuous wave fiber laser with a maximum output of 6.3 kW. Because brittle regions form easily in titanium as a result of oxidation or nitriding, the weld must be protected from the atmosphere by using an appropriate shielding gas. Experiments were performed by changing the type and the flow rate of shielding gases to obtain the optimal shielding condition, and the weldability was then evaluated. The degree of oxidation and nitriding was distinguished by observing the color of beads, and weld microstructure was observed by using an optical microscope and a scanning electron microscope. The mechanical properties of the weld were examined by measuring hardness. When the weld was oxidized or nitrified, the bead color was gray or yellow, and the oxygen or nitrogen content in the bead surface and overall weld tended to be high, as a result of which the hardness of the weld was thrice that of the base metal. A sound silvery white bead was obtained by using Ar as the shielding gas.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.2
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• pp.166-173
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• 1999

Commercial carbon steels containing 0.2~0.55 wt.----C were plasma-nitrided or plasma nitrocarburized at $550^{\circ}C$ for 21.6Ks using $H_2-N_2$ or $H_2-N_2$-CO mixed gas respectively. The characteristics of hardening and wear-resistance of each treatment were studied and compared. And also microstructure of nitrided layer and nitrides formed in compound layer near surface were studied. All plasma-nitrided steels investigated showed remarkable increase of surface hardness with the increase of carbon content. But nitrocarburized steels resulted in higher surface-hardness than plasma-nitrided steels, which means that nitrocarburized has higher surface-hardening effect. Plasma-nitrided steels showed hardness increase in through-thickness direction near surface. And also nitrocarburized steels showed similar hardness distribution in through-thickness direction to that of plasma-nitrided steel. However, nitrocarburized steels had higher cross-sectional maximum-hardness than plasma-nitrided steels as much as 100Hv. Wear test showed that the amount of specific wear was reduced by both plasma-nitriding and nitrocarburized, showing that the amount of specific wear was not related to the hardness. But non-treated specimen showed that the amount of specific wear was related to the hardness.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.312-316
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• 1999

The interfacial structure of duplex treated AISI 4140 consisting of iron nitride and TiN layer was characterized by optical microscope, SEM and XRD. A black layer was formed from the decomposition of iron nitride during Ti ion bombardment. The black layer was characterized as an a-Fe phase transformed from the iron nitride by XRD. In order to identify the formation mechanism of the black layer, a thermal analysis of iron nitride undertaken by DSC method. As an iron nitride was mostly consisted of ${\gamma}$'-Fe$_4$N and $\varepsilon$-$Fe_3$N phase after plasma nitriding, in this study, a ${\gamma}$'$-Fe_4$N and $\varepsilon$-$Fe_3$N powders were separately prepared by the different processing conditions of gas nitriding of iron powder in the fluidized bed. From the DSC thermal analysis, the phase transformation of ${\gamma}$'$-Fe_4$N, $\varepsilon$-$Fe_3$N was followed the path of transformation; $ \Upsilon{'}-Fe_4$Nlongrightarrow${\gamma}$-Felongrightarrowa-Fe and of $\varepsilon$-$Fe_3$Nlongrightarrow$\varepsilon$-$Fe_{2.5}$ /N+${\gamma}$'$-Fe_4$Nlongrightarrow${\gamma}$'-Fe$_4$Nlongrightarrow${\gamma}$longrightarrowFelongrightarrowalongrightarrowFe, respectively. It explains the reason why the $\varepsilon$ $-Fe_3$N phase disappeared in the first time and then ${\gamma}$'-Fe$_4$N in the formation of the black layer in the duplex coating.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.5
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• pp.263-268
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• 2010

This investigation was focused on the low temperature tensile properties, phase change, changes in nitrogen content and corrosion resistance in the 22Cr-5Ni-3Mo duplex stainless steel after high temperature gas nitriding and solution annealing (HTGN-SA). From the HTGN-SA treatment, the duplex (ferrite + austenite) phase changed into austenite single phase. The nitrogen content of austenite single-phase steel showed a value of ~0.54%. For the HTGN-SA treated austenitic steel, tensile strength increased with lowering test temperature, on the other hand elongation showed the maximum value of 28.2% at $-100^{\circ}C$. The strain-induced martensitic transformation gave rise to lead the maximum elongation. After HTGN-SA treatment, corrosion resistance of the austenite single-phase steel increased remarkably compared with HTGN- treated steel.

• Design & Manufacturing
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• v.13 no.1
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• pp.13-18
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• 2019

The size and prospects of the domestic semiconductor equipment market are increasing every year. In the case of various parts used inside semiconductor equipments, high durability such as high strength and abrasion resistance is demanded. Particularly, the gases used in semiconductor production processes are toxic. In order to prevent such toxic gas leakage, a precision processing technique and a surface treatment technique for preventing corrosion are required. Electro-polishing is an electro-chemical method of polishing a metal surface to make it smooth and polished. Electro-polishing is mainly used in the finishing process of metal surface. Unlike mechanical polishing, electro-polishing is used in many fields, such as fine chemical etching equipment, since no damaged layer or burr, fine polishing groove and particles are generated. However, in order to withstand the gas used in the semiconductor equipment, the parts must have high corrosion resistance. However, the surface hardness generally become lowered through electro-polishing. Therefore, in this study, surface hardness were experimentally observed before and after electro-polishing. Then, a method of improving hardness by preparing a nitrided layer by plasma ion nitriding treatment.

• Journal of the Korean institute of surface engineering
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• v.30 no.3
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• pp.167-174
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• 1997

WC-C0 base cemented carbides were plasma nitrided to obtain more hadened surface layer. The surface hardness of Hv1338 which is higher than a non-treated ane by 30%, and the hardened layer thickness of about 50$\mu\textrm{m}$ were obtained by the treatment of 3hrs under the conditions of $550^{\circ}C$, and 5torr of gas pressure of which composition was 1:1 of $N_2:H_2$. The nitrided surfaces has WIN and W2N phases in the non-coated samples and AIN phase in the alumina coated sampled as the results of X-ray results, and showed surface roughnness of 5$\mu\textrm{m}$ which were caused by the sputtering action of the plasma gasee. The hardenened layer exihibits an enhanced wear resistance the cuttability test.

• Journal of the Korean institute of surface engineering
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• v.28 no.6
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• pp.361-367
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• 1995

When steels are heated at $1000^{\circ}C$ in a fused borax bath containing $V_2O_5$ and $B_4C$powders, vanadium carbide layers are formed on the steel surfaces. Since a decrease in carbon concentration and in microhardness in the substrate just below the carbide layer has been observed, gas nitrocarburizing and vanadium carbide forming processes were combined to form a V(C,N) type layer which prevented the decrease in carbon concentration in the substrate. EPMA analysis was done for this V(C,N) type layer. Hardness just below the layer and wear resistance properties of such treated specimens were investigated.