Showing papers on "Austenitic stainless steel published in 1986"

The air oxidation of an austenitic Fe-Mn-Cr stainless steel for fusion-reactor applications

Abstract: The oxidation in air of an austenitic Fe-Mn-Cr steel containing 17.8 Mn, 9.5 Cr, 1.0 Ni, 0.27 C, and 0.03 N was studied over the range 700–1000°C. Oxidation of surface-abraded samples at “low” temperatures, 700–750°C, resulted in only Mn2O3 containing dissolved chromium, except at corners, where large nodules containing spinel and manganowustite formed. The Mn2O3 layer grew into the substrate forming a globular-type film. This growth mode was the result of slow interdiffusion in the alloy after the cold-worked surface layer had been recrystallized and/or consumed, as evidenced by the formation of a ferrite layer subjacent to the scale and by the instability of the planar interface. No internal oxidation was observed beneath the Mn2O3 film at either 700 or 750°C. Samples oxidized in the“high-temperature” region, 800–1000°C, exhibited vastly different behavior, forming thick stratified scales at long times (24 hr), the scales consisting of a very thin outer layer of Mn2O3 (with appreciable iron in solution), Fe-Mn spinel beneath the outer layer, and a thick inner layer of manganowustite and a chromium-containing spinel. No chromium was found in the outer two layers. A thin layer of nearly pure Fe2O3 formed between Mn2O3 and the outer spinel.

Method of manufacturing surgical implants from cast stainless steel and product

Abstract: A surgical implant is disclosed manufactured from cast austenitic stainless steel and cold-forged to a final shape. The endoprosthesis is initially a preform which is cast oversized in shape and dimensions. It is then compressed using the cold-forging process to its final size and shape. Using a cast material as a starting material and then compressing it substantially reduces the porosity of the material and increases its strength compared to a machined product from a wrought material.

Structure and properties of ion-nitrided stainless steels

Abstract: The structure and properties of ion-nitrided layers on several stainless steels, 410 martensitic stainless steel, 430 ferritic stainless steel and 321 austenitic stainless steel, has been studied under varying process conditions with microhardness-depth correlations, optical microscopy and transmission electron microscopy. The process variables studied include time (2 to 10 h) and temperature (400 to 600° C). The highest case depth values and hardness levels were observed in martensitic stainless steels. The lowest case depths were observed in austenitic stainless steel. In general, the behaviour of matensitic and ferritic stainless steels were similar. All three steels showed increasing case depths and decreasing surface hardnesses with increasing ion-nitriding temperatures and times. Nitriding depth was found to be parabolic with ion nitriding time in all three steels at all ion-nitriding temperatures investigated, the nitriding reaction being faster in martensitic stainless steel than the others. Electron microscopy showed that almost no structural difference arises in the core of ferritic and austenitic stainless steels whereas recrystallization of the martensitic structure was observed in the core of martensitic steel following ion nitriding. Electron microscopy results also showed that ion nitriding produces platelets or disc-shaped precipitates on {001} matrix planes, coherent with the matrix. These platelets showed a striated morphology which is thought to be the result of the elastic strain in the matrix.

Solid-state bonding of alumina to austenitic stainless steel

Abstract: A low temperature and low pressure bonding process for alumina and 316L austenitic stainless steel has been developed using a titanium/molybdenum laminated interlayer. The intermetallic compounds of Ti3Al (or Ti2/Al) and TiAl were formed at the alumina/titanium interface on bonding at above 1273 K. The activation energy of the layer growth was about 142 kJ mol−1. The construction of Al2O3/Ti/Mo/steel gave the most stable joints. The highest tensile strength was above 60 MPa with a titanium 0.4 to 0.6mm thick/molybdenum 0.4 to 0.5 mm thick interlayer on bonding at 1273 K for 3 h under pressure of 12 MPa.

The coking kinetics of heat resistant austenitic steels in hydrogen-propylene atmospheres

Abstract: The kinetics of coke formation on several commercial Fe-Ni-Cr alloys used in the construction of ethylene steam crackers, nickel and copper were investigated over the temperature range 450 to 1000‡ C in hydrogen-propylene atmospheres using a tubular microbalance reactor. Between 900 and 1000‡ C steady state coking was controlled by gas-phase pyrolysis and similar coking rates were observed for all materials. At 900‡ C alloy carburization led to lengthy periods of parabolic kinetics before the onset of steady state. Below 900‡ C alloy coking rates were between those of copper and nickel. Major differences in coking rates of alloys were only observed below 800‡ C and arise from variations in the effectiveness of chromium carbide scales in excluding the hydrocarbon atmosphere from contact with the underlying nickel-rich and iron-rich alloy.

Ordering in Fe-Mn-Al-C austenite

Abstract: Etude par microscopie electronique en transmission de la precipitation de carbures ordonnes de type L1 2 . Influence des traitements thermiques et de la composition des alliages

Forming stable welded joints between dissimilar metals

Abstract: A method of forming a stable welded joint between low alloy steels and austenitic stainless alloy steels which is characterized by increased resistance to chemical corrosion and mechanical stress and which has a greatly extended service lifetime. The method comprises forming a deposit of a low alloy steel containing niobium onto a portion of low alloy steel to be welded; heating the deposit to a first temperature at which all carbides present therein have dissolved; quenching the deposit and forming a solid solution of the elements of the dissolved carbides; and reheating the deposit for a time period and at a second temperature sufficient to form niobium carbides therein containing substantially all of the carbon present in the deposit. The austenitic stainless steel portion is welded to the deposit using a substantially nonferrous nickel-based alloy as the weld filler material, thereby joining the low alloy steel portion to the austenitic stainless steel portion.

Stability of nitrogen-rich titanium nitride and zirconium nitride films

Abstract: Thin titanium nitride (TiN) and zirconium nitride (ZrN) films containing excess nitrogen up to 62 and 65 at. % N, respectively, were deposited on austenitic stainless steel sheet substrates by triode ion plating at about 823 K. The nitrogen content of the films was determined using the nuclear resonance broadening technique based on the 15N(p,αγ)12C nuclear reaction and x‐ray diffraction was used to study the phase compositions. Annealing experiments in evacuated quartz tubes were carried out at 773 and 1173 K to test the stability of the coatings. The results showed no essential differences for TiN before and after heat treatment. Slight indications of diffusion accompanied with the transformation of remaining α‐Zr to ZrN were found in the case of ZrN films after heat treatment at the higher temperature of 1173 K.

A Comparison between Grain Boundary Chromium Depletion in Austenitic Stainless Steel and Corrosion in the Modified Strauss Test

Abstract: This paper reports a detailed comparison between an analytical electron microscopy (AEM) study of the chromium depletion process around grain boundary carbides in an austenitic stainless steel (SS) and the corrosion results for the same steel tested in the modified Strauss test. The comparison shows that chromium depletion is the primary cause for attack in this test. The occurrence of corrosion, shape of the corroded region at the grain boundary, length of attack along a boundary, and depth of corrosion penetration into the sample can all be explained in terms of the chromium depletion detected by AEM. The only disagreement is in the width of the corroded region at the grain boundary. It is always wider than that of the depleted material.

Austenitic free cutting stainless steels

Abstract: An austenitic stainless steel having improved free cutting properties is disclosed, which consists essentially of, on a weight ratio, C≦0.2%. Si≦2.0%, Mn≦2.0%, 7.5%≦Cr≦30.0%, Ni≦40.0%, 0.005%≦Bi≦0.50%, 0.0003%≦B≦0.10%, 0.002%≦S≦0.40%, P≦0.02%, N≦0.05% and/or O≦0.005% and the balance being Fe.

Effect of Nitrogen on Low Cycle Fatigue Behavior of Austenitic Stainless Steel

Abstract: The effect of nitrogen on low cycle fatigue behavior of 18.5Cr-15Ni austenitic stainless steel has been investigated over a temperature range from room temperature to -162°C. Results obtained are as follows:(1) N induces cyclic hardening, followed by cyclic softening to saturation over the whole temperature range.(2) The cyclic softening at room temperature may be attributed to dislocation rearrangement from planar arrays to cellular ones, while at -162°C, it may be attributed to the increase in mobile dislocation density.(3) Based on these results, it is proposed that a zone of short range order (SRO) may be formed by the addition of N, and the interaction between dislocations and the SRO-zone may be responsible for the observed cyclic behaviors. Especially at -162°C the cyclic behavior is controlled by a thermally activated process of dislocation motion in a short range stress field.(4) N improves the fatigue life over the whole temperature range by reducing cyclic hardening and promoting cyclic softening.

High-strength conductors and process for manufacturing same

Abstract: Pliable high-strength conductors for use in electronic instruments involving frequent movements, such as robots. They comprise a core layer of austenitic stainless steel and a covering layer of copper, or its alloy. Higher resistance to flexing fatigue is ensured by the addition of stainless steel as a core. An austenitic stainless steel wire having a specific diameter is employed and the percentage of sectional area of the covering layer to the total sectional area is specified.