Mechanical and metallurgical properties of friction welded AISI 304 austenitic stainless steel

Owing to the superior properties, of stainless steel it is pertinent to make use of it in various automotive, aerospace, nuclear, chemical and cryogenic applications. It is observed that a wide range of dissimilar materials can be easily integrated by solid phase bonding techniques, such as friction welding and explosive bonding. This study mainly focuses on friction welding of AISI 304 austenitic stainless steel. The friction processed joints are evaluated for their integrity and quality aspects. Friction welding of austenitic stainless steel was carried out using a KUKA friction welding machine (Germany). As the friction time increased, the fully plastically deformed zone (region I) in the vicinity of the bond line becomes increased. In contrast, an increase in friction time will decrease the region (region II) where the grains are partly deformed and grown. Tensile test results indicated that, the joint strength is decreased with an increase of the friction time. The detailed fractographic observation confirmed that the rupture occurred mostly at the joint zone and partly through the base material.     

Mechanical and metallurgical properties of friction welded AISI 304 austenitic stainless steel

Owing to the superior properties, of stainless steel it is pertinent to make use of it in various automotive, aerospace, nuclear, chemical and cryogenic applications. It is observed that a wide range of dissimilar materials can be easily integrated by solid phase bonding techniques, such as friction welding and explosive bonding. This study mainly focuses on friction welding of AISI 304 austenitic stainless steel. The friction processed joints are evaluated for their integrity and quality aspects. Friction welding of austenitic stainless steel was carried out using a KUKA friction welding machine (Germany). As the friction time increased, the fully plastically deformed zone (region I) in the vicinity of the bond line becomes increased. In contrast, an increase in friction time will decrease the region (region II) where the grains are partly deformed and grown. Tensile test results indicated that, the joint strength is decreased with an increase of the friction time. The detailed fractographic observation confirmed that the rupture occurred mostly at the joint zone and partly through the base material.     

Tribological behaviour of AISI 316L stainless steel for biomedical applications

Abstract

The aim of this research is to study the tribological behaviour of AISI 316L stainless steel for surgical implants (total hip prosthesis). The tribological behaviour is evaluated by wear tests, using tribometers ball on disc and sphere on plane. These tests consisted of measuring the weight loss and the friction coefficient of stainless steel (SS) AISI 316L. The oscillating friction and wear tests have been carried out in ambient air with an oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a and ASTM G133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm s^?1). A ball of 100Cr 6, 10 mm in diameter, is used as counter pairs. These tribological results are compared with those carried out with a tribometer type pin on disc under different conditions of normal load applied P (19·43, 28 and 44 N) and sliding speed (600 and 1020 rev min^?1). The behaviour observed for both samples suggests that the wear and friction mechanism during the tests is the same, and to increase the resistance to wear and friction of biomedical SS AISI 316L alloy used in total hip prosthesis (femoral stems), surface coating and treatment are necessary.     

Direct laser cladding of SiC dispersed AISI 316L stainless steel

The present study concerns development of SiC dispersed (5 and 20 wt%) AISI 316L stainless steel metal-matrix composites by direct laser cladding with a high power diode laser and evaluation of its mechanical properties (microhardness and wear resistance). A defect free and homogeneous composite layer is formed under optimum processing condition. The microstructure consists of partially dissociated SiC, Cr₃C₂ and Fe₂Si in grain refined stainless steel matrix. The microhardness of the clad layer increases to a maximum of 340 VHN (for 5% SiC dispersed) and 800 VHN (for 20% SiC dispersed) as compared to 150 VHN of commercially available AISI 316L stainless steel. Direct laser clad SiC dispersed AISI 316L stainless steel has shown an improved wear resistance against diamond surface with a maximum improvement in 20% SiC dispersed AISI 316L stainless steel. The mechanism of wear was predominantly abrasive in nature.     

An experimental study on bending fretting fatigue characteristics of 316L austenitic stainless steel

Bending fretting fatigue tests of 316L austenitic stainless steel plates against 52100 steel cylinders have been carried out under same normal load and varied bending loads. Tests of plain bending fatigue were carried out as a control group. The S-N curves of the bending fatigue were made. The results indicated that there was an obvious drop of life under the condition of bending fretting fatigue due to higher local contact stress. A dislocation model of micro-crack nucleation mechanism, as a manner of zig-zag mode, was created to explain the nucleation of fretting fatigue cracks.     

EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel

The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 °C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre‐existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of {111} slip planes. The corresponding misorientations were small and largely displayed a non‐cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub‐boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub‐boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels.     

316L型不锈钢的耐蚀性分析

探讨316L型不锈钢发生腐蚀的原因,在实际生产中加以注意尽量减少腐蚀给设备带来的损坏,保证生产的正常进行。     

Mechanical cyclic behaviour of 316L welded joint

To take into account the reduced fatigue strength of welded joints, a reduction factor on the fatigue curves was introduced into the RCC-MR French nuclear design and construction code. To better assess this factor, a previous work on large plates showed that the mechanical behaviour of a welded assembly is influenced by the geometry of the weld and by the interaction of the different cyclic plastic behaviour of the two materials: base metal (BM) and weld metal (WM). A new program was performed consisting in tests on butt welded pipe connections (4 points bending), fatigue tests on uniaxial specimens (uniaxial tensile-compressive load) and finite elements calculations. The uniaxial fatigue tests have been carried out on specimens extracted form a butt welded pipe connection manly at 600 °C. Some tests have been carried out at ambient temperature and have permit to realise some ESPI measurements to have a better knowledge of the strain gradients at some stage of the fatigue tests. But the use of ESPI sensor requires some experimental conditions which are hardly adaptable to real fatigue test conditions. Nevertheless, by using concurrently some classic extensometers sensors, new observations can be done on the fatigue specimens behaviour.     

Corrosion-wear mechanisms of hard coated austenitic 316L stainless steels

Austenitic stainless steels like 316L are amongst the most commonly selected structural alloys for use in corrosion environments. Unfortunately, their resistance to surface degradation caused during sliding contacts with other materials, in such environments is poor. Here, a synergistic combination of mechanical (wear) and chemical (corrosion) processes, known as corrosion-wear processes, are responsible for causing surface material loss. Accordingly, efforts are being made to identify surface treatments that can enhance the corrosion-wear resistance of 316L and similar alloys. One plausible solution is to apply thin hard coatings (∼5-10 μm thick) using various plasma-based technologies. In practice, this is often fraught with difficulty because of the complex nature of the pervading corrosion-wear mechanisms. This paper presents our recent work that has identified three major corrosion-wear mechanisms that must be minimised if a successful surface engineering design is to be achieved for corrosion-wear protection. These are: Type I—the removal of the coating passive film during sliding contact; Type II—galvanic attack of the substrate resulting in blistering of the coating and; Type III—galvanic attack of the counterface material leading to abrasion of the coating during subsequent sliding contact.     

Relation between roughness and processing conditions of AISI 316L stainless steel treated by ultrasonic shot peening

This article assessed the roughness induced by ultrasonic shot peening. Surface properties of AISI 316L steel specimens were modified through the variation of ultrasonic shot-peening parameters (shot material, shot diameter, sonotrode amplitude vibration and coverage). Each surface was characterized using fifty surface roughness parameters and two types of robust Gaussian filter (low pass and high pass) associated with twenty one cut-off lengths. For each type of processing parameter, the most relevant roughness parameter and its corresponding length scale and filter were found. A linear relationship was identified between the four ultrasonic shot-peening parameters and the mean density of furrows with a coefficient of determination equal to 0.97.     

Eutectic bonding of austenitic stainless steel 316L to magnesium alloy AZ31 using copper interlayer

The eutectic bonding of magnesium alloy (AZ31) to austenitic stainless steel alloy (316L) was performed using pure Cu interlayers. The effect of hold time on the microstructural developments across the joint region and the related effect on bond shear strength were studied at a bonding temperature of 530°C. The bonding process took place through a sequential occurrence of solid-state diffusion of Cu into the magnesium alloy, eutectic phase formation, interlayer dissolution, and isothermal solidification. A (Mg–Cu–Al) ternary intermetallic phase formed within the joint and concentrated into the center of the bond during the solidification stage increasing the hardness value to a maximum average of VHN313 while the maximum recorded bond shear strength was 57 MPa achieving 69% of the AZ31 shear strength and about three to four times of the adhesive joints.     

Effect of hydrogen on tensile flow and failure mechanism of low nickel-type 316L austenitic stainless steel

Journal of Mechanical Science and Technology - An investigation of the effects of hydrogen on tensile flow, strain-hardening and fracture characteristics of low nickel-type 316L austenitic...     

Structural analysis and intergranular corrosion tests of AISI 316L steel

Pure AISI 316L steel is investigated after solution heat treatment (1050 °C/H₂O) and structural sensitization (650 °C). Two quite different intergranular corrosion tests are used to determine the degree of structural sensitization due to the precipitation of secondary phases along the grain boundaries (mainly the M₂₃C₆ and σ‐phase): the oxalic acid etch test and the electrochemical potentio‐kinetic reactivation test. Generally, the dissolution of chromium‐rich carbides (M₂₃C₆) is provoked by oxalic acid etch tests, whereas the chromium‐depleted zones, in the vicinity of chromium‐rich carbides (M₂₃C₆), are attacked by electrochemical potentio‐kinetic reactivation tests. Both intergranular corrosion tests are used to determine the maximum degree of structural sensitization. Thus structural analysis by carbon replicas reveals the Laves phase, and both the M₂₃C₆ and (Cr,Mo)_x(Fe,Ni)_y phases. The results of intergranular corrosion tests are related to the findings of the structural analysis.     

316L不锈钢的车削精加工研究

笔者对316L不锈钢材料的切削加工特点进行分析,并从刀具材料的选用以及切削用量、切削液的选择3方面对316L不锈钢零件的车削精加工进行了分析和研究.     

Effect of sigma phase on near-threshold fatigue crack growth behavior and ultrasonic evaluation in AISI 316L stainless steel

In this work, we examined the influence of microstructural changes, such as an intermetallic sigma (??) phase, on the fatigue behavior of high-temperature aged AISI 316L stainless steel. Nondestructive ultrasonic test and fatigue crack growth tests were performed to determine the threshold stress intensity factor of these artificially aged specimens. Ultrasonic test results characterizing the microstructural changes were compared with those of the fatigue tests to propose an empirical formula capable of predicting the threshold stress intensity factor by a nondestructive method. We observed a strong correlation between the increase in the volume fraction of the ?? phase and the decrease of ??K_th. Ultrasonic velocity increased in response to the coarsening behavior of the ?? phase in the vicinity of the grain boundaries.     

Fretting fatigue properties of plasma nitrided AISI 316 L stainless steel: Experiments and finite element analysis

This study investigates the effects of thickness, hardness and composition of modified layer on the plain and fretting fatigue properties of the nitrided 316 L steel plasma nitrided under various processing conditions. Fretting fatigue behaviour of untreated and nitrided material is also analysed with the finite element method. Experimental and theoretical fatigue life results are compared. The result indicates that the nitriding process improved the fretting fatigue properties of 316 L stainless steel. The experimental test results are close to theoretical fretting fatigue life results, thus it yields that the established model in the numerical analysis is consistent in this regard.     

Fretting fatigue properties of plasma nitrided AISI 316 L stainless steel: Experiments and finite element analysis

This study investigates the effects of thickness, hardness and composition of modified layer on the plain and fretting fatigue properties of the nitrided 316 L steel plasma nitrided under various processing conditions. Fretting fatigue behaviour of untreated and nitrided material is also analysed with the finite element method. Experimental and theoretical fatigue life results are compared. The result indicates that the nitriding process improved the fretting fatigue properties of 316 L stainless steel. The experimental test results are close to theoretical fretting fatigue life results, thus it yields that the established model in the numerical analysis is consistent in this regard.     

Delamination wear of metal injection moulded 316L stainless steel

The wear behavior of metal injection moulded (MIM) stainless steels was studied using a pin-on-disc apparatus under dry sliding conditions. Pin specimens were MIM 316L stainless steel, while disc specimens were wrought 316L stainless steel. At low sliding speeds (0.2–0.6 m/s), the wear rates gradually decreased with increasing sliding speed, but then increased at high sliding speeds (0.6–2 m/s). The adhesive-induced delamination wear dominated at low sliding speeds, while abrasive-induced delamination wear dominated at high sliding speeds. At low sliding speeds, the surface densification occurred on the worn surface of pin specimens, hence no difference was found between the wear resistances of MIM pins containing 2% and 6% porosity. In contrast, the abrasive-induced delamination wear at high sliding speeds was enhanced by porosity; therefore the wear rates of MIM pins containing 6% porosity were higher than those of MIM pins containing 2% porosity.     

TEM and AES investigations of the natural surface nano‐oxide layer of an AISI 316L stainless steel microfibre

The chemical composition, nanostructure and electronic structure of nanosized oxide scales naturally formed on the surface of AISI 316L stainless steel microfibres used for strengthening of composite materials have been characterised using a combination of scanning and transmission electron microscopy with energy‐dispersive X‐ray, electron energy loss and Auger spectroscopy. The analysis reveals the presence of three sublayers within the total surface oxide scale of 5.0–6.7 nm thick: an outer oxide layer rich in a mixture of FeO.Fe₂O₃, an intermediate layer rich in Cr₂O₃ with a mixture of FeO.Fe₂O₃ and an inner oxide layer rich in nickel.