scholarly journals Influence of Machining on Low Temperature Surface Hardening of Stainless Steel

2019 ◽  
Author(s):  
Ulli Oberste-Lehn ◽  
Andreas Karl ◽  
Chad Beamer
Keyword(s):  
Corrosion Resistance ◽  
Low Temperature ◽  
Stainless Steels ◽  
Surface Hardening ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Production Costs ◽  
Machining Process ◽  
Machining Operations ◽  
Temperature Surface

Abstract The main goal of low temperature surface hardening of austenitic stainless steels is a significant increase of surface hardness while at the same time maintaining the superior corrosion resistance of these alloys. The treatment temperature has to be low enough to achieve a precipitation free diffusion zone, yet high enough to allow sufficient diffusion depths needed for technical applications. The results are often influenced by the machining of parts prior to the surface treatment. Best results are usually achieved on solution annealed and (electro-)polished surfaces, but customer needs for certain manufacturing routes, strength considerations and overall production costs often do not allow for such additional processes. This paper shall give a basic overview on machinability of austenitic stainless steels and how different machining operations like turning, cold forming, grinding and additive manufacturing influence the result of low temperature surface hardening. Possible machining process optimizations for the different machining operations are presented in order to increase diffusion depth, surface hardness, reproducibility and corrosion resistance without altering the hardening process parameters.

scholarly journals Surface Modification of a Nickel-Free Austenitic Stainless Steel by Low-Temperature Nitriding

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1845
Author(s):  
Francesca Borgioli ◽  
Emanuele Galvanetto ◽  
Tiberio Bacci
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Low Temperature ◽  
Stainless Steels ◽  
Volume Fraction ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Surface Layers ◽  
Modified Surface

Low-temperature nitriding allows to improve surface hardening of austenitic stainless steels, maintaining or even increasing their corrosion resistance. The treatment conditions to be used in order to avoid the precipitation of large amounts of nitrides are strictly related to alloy composition. When nickel is substituted by manganese as an austenite forming element, the production of nitride-free modified surface layers becomes a challenge, since manganese is a nitride forming element while nickel is not. In this study, the effects of nitriding conditions on the characteristics of the modified surface layers obtained on an austenitic stainless steel having a high manganese content and a negligible nickel one, a so-called nickel-free austenitic stainless steel, were investigated. Microstructure, phase composition, surface microhardness, and corrosion behavior in 5% NaCl were evaluated. The obtained results suggest that the precipitation of a large volume fraction of nitrides can be avoided using treatment temperatures lower than those usually employed for nickel-containing austenitic stainless steels. Nitriding at 360 and 380 °C for duration up to 5 h allows to produce modified surface layers, consisting mainly of the so-called expanded austenite or gN, which increase surface hardness in comparison with the untreated steel. Using selected conditions, corrosion resistance can also be significantly improved.

Low Temperature Nitriding of a Martensitic Stainless Steel

2011 ◽  
Vol 312-315 ◽  
pp. 994-999 ◽  
Author(s):  
Riza Karadas ◽  
Ozgur Celik ◽  
Huseyin Cimenoglu
Keyword(s):  
Wear Resistance ◽  
Corrosion Resistance ◽  
Low Temperature ◽  
Stainless Steels ◽  
Martensitic Stainless Steel ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
S Phase ◽  
Martensitic Stainless Steels ◽  
Wear And Corrosion

Nitriding is as an effective technique applied for many years to improve the surface hardness and wear resistance of low carbon and tool steels [1]. In the case of stainless steels, increase of surface hardness and wear resistance accompany by a drop in corrosion resistance due to the precipitation of CrN. In this respect, many attempts have been made to modify the surfaces of austenitic stainless steels to increase their surface hardness and wear resistance without scarifying the corrosion resistance [2-6]. It is finally concluded that, nitriding at temperatures lower than conventional nitriding process (which is generally about 550°C) has potentiality to produce a nitrogen expanded austenite (also known as S-phase), on the surface without formation of CrN. Due to the superb properties of the S-phase, the low temperature nitrided austenitic stainless steels exhibit very high surface hardness, a good wear resistance, and more importantly, an excellent corrosion resistance. Recently some attempts have been made to apply low temperature nitriding to martensitic stainless steels, which are widely used in the industries of medicine, food, mold and other civil areas [7-9]. In these works, where nitriding has been conducted by plasma processes, superior surface hardness, along with excellent wear and corrosion resistances have been reported for AISI 410 and AISI 420 grade martensitic stainless steels. This work focuses on low temperature gas nitriding of AISI 420 grade martensitic stainless steel in a fluidized bed reactor. In this respect the microstructures, phase compositions, hardness, wear and corrosion behaviours of the original and nitrided martensitic stainless steels have been compared.

Low Temperature Plasma Surface Alloying of Austenitic Stainless Steels

2006 ◽  
Vol 118 ◽  
pp. 85-90 ◽  
Author(s):  
Y. Sun ◽  
E. Haruman
Keyword(s):  
Low Temperature ◽  
Stainless Steels ◽  
Layer Structure ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Low Temperature Plasma ◽  
Surface Alloying ◽  
Temperature Plasma ◽  
Plasma Surface ◽  
Plasma Surface Alloying

This paper gives a brief review on the three low temperature plasma surface alloying processes that have been developed in recent years to engineer the surfaces of austenitic stainless steels to achieve much enhanced surface hardness and wear resistance, without compromising their corrosion resistance. These include low temperature plasma nitriding, low temperature plasma carburizing and the newly developed hybrid process involving the simultaneous incorporation of nitrogen and carbon to form a dual layer structure. The processing, structural and property characteristics of each process are discussed briefly in this paper.

scholarly journals HARDNESS OF NITRIDED LAYERS TREATED BY PLASMA NITRIDING

2020 ◽  
Vol 27 ◽  
pp. 53-56
Author(s):  
Zdeněk Joska ◽  
Zdeněk Pokorný ◽  
Jaromír Kadlec ◽  
Zbyněk Studený ◽  
Emil Svoboda
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Stainless Steels ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Aisi 316L ◽  
Aisi 304 ◽  
Measurement Surface

Stainless steels, particularly the austenitic stainless grades are widely used in many industries due to good corrosion resistance, but very poor mechanical properties as surface hardness and wear resistance limit its possible use. Plasma nitriding is one of the few ways to increase the surface hardness of these steels, even though this will affect its corrosion resistance. This paper focuses on the description of the mechanical properties of nitrided layers in the two most widespread austenitic stainless steels AISI 304 and AISI 316L. The microstructure and properties of nitrided layers were evaluated by metallography and microhardness measurement. Surface properties of nitrided steels were characterized by Martens hardness. The results show that plasma nitriding created very hard nitrided layers with thickness about 40 μm and microhardness about 1300 HV0.05. Surface hardness measurements have shown that the maximum values for both steels are about 8.5 GPa, but have different behaviour under higher loads, when the AISI 316L nitrided layer began to crack on the surface and sink.

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