Austenitic Stainless Steel X5CrNi18-10 Research Articles

Residual Stress Engineering for Wire Drawing of Austenitic Stainless Steel X5CrNi18-10 by Variation in Die Geometries-Effect of Drawing Speed and Process Temperature.

As a result of conventional wire-forming processes, the residual stress distribution in wires is frequently unfavorable for subsequent forming processes such as bending operations. High tensile residual stresses typically occur in the near-surface region of the wires and can limit further application and processability of the semi-finished products. This paper presents an approach for tailoring the residual stress distribution by modifying the forming process, especially with regard to the die geometry and the influence of the drawing velocity as well as the wire temperature. The aim is to mitigate the near-surface tensile residual stresses induced by the drawing process. Preliminary studies have shown that modifications in the forming zone of the dies have a significant impact on the plastic strain and deformation direction, and the approach can be applied to effectively reduce the process-induced near-surface residual stress distributions without affecting the diameter of the product geometry. In this first approach, the process variant using three different drawing die geometries was established for the metastable austenitic stainless steel X5CrNi18-10 (1.4301) using slow (20 mm/s) and fast (2000 mm/s) drawing velocities. The residual stress depth distributions were determined by means of incremental hole drilling. Complementary X-ray stress analysis was carried out to analyze the phase-specific residual stresses since strain-induced martensitic transformations occurred close to the surface as a consequence of the shear deformation and the frictional loading. This paper describes the setup of the drawing tools as well as the results of the experimental tests.

Laser-assisted micro-milling of austenitic stainless steel X5CrNi18-10

This paper presents a novel Laser-Assisted Micro-Milling (LAMM) process of austenitic stainless steel X5CrNi18-10. The LAMM process is compared with the conventional micro-milling process. Ultra-short pulsed laser radiation is utilized for the structuring of the workpiece surface prior to the micro-milling process. Different laser structures are produced on the workpiece surface at a constant laser scanning speed with various laser powers and laser line spans. The high performance of the developed process is shown by experimental investigations. The effect of laser structuring on the micro-milling forces and temperature indicated the superior performance of the new LAMM process. Cutting forces and temperature could be reduced by up to 70% and 50%, respectively. The results of conventional micro-milling showed that increasing the cutting speed, at a constant undeformed chip thickness, reduced the micro-milling forces. Increasing the cutting speed from 50 to 250 m/min halved both the trust and normal forces, while it slightly improved the surface roughness. On the other hand, increasing the feed per tooth degraded the surface roughness and increased the cutting forces. Furthermore, in conventional milling the workpiece was subjected to high plastic deformation during the cutting process, while side flow, smeared material, metal debris, and cavities were observed on the workpiece surface.

Cavitation Erosion Resistance of Laser Beam Nitride Layers of X5CrNi18-10 Stainless Steel

The use of nitration in technical applications, as thermochemical treatment, regardless of the used method (ionic, gas or laser beam nitration) is realized to obtain a nitrogen rich layer, which increase the resistance to shock or abrasion, as a result of the high hardness obtained. All the previous cavitation researches showed that hardness is an important mechanical properties, for cavitation erosion resistance increase. The present paper show some results regarding the cavitation erosion behavior of laser beam nitrated layers. As basic material was used the austenitic stainless steel X5CrNi18-10. This material is frequently used for manufacturing details subjected to cavitation, such as valves, drawers of hydraulic distribution and regulation devices, or the retaining ring for butterfly valves. There were used three power regimes of the laser beams: 120 W, 180 W and 240 W. To obtain cavitation erosion was used the standard device with piezo-ceramic crystals of Timisoara Polytechnic University Cavitation Laboratory. The cavitation erosion comparisons, both with the basic material subjected only to the common thermochemical treatments and with the laboratory cavitation standard steel (OH12NDL), show that the nitrated surfaces presents increased cavitation erosion behavior, the principal factor being the important hardness increase of the nitrated layer. We mention also, that for higher laser beam powers the thickness of the nitrated layer increases. All the images obtained at the end of tests show that the cavitation exposure was stopped before overtaking the nitrated layer. So, all our results concern only the hardened layers.

Influence of the machine hammer peening technology on the surface near material structure of stainless steel X5CrNi18-10

Machine hammer peening (MHP) is a mechanical surface treatment process that leads to increased hardness and induces compressive residual stresses in surface-near layers of the peened workpiece. This fact, in combination with the possibility of phase transformation of the crystal lattice of a processed metastable austenitic to martensitic structure by the application of machine hammer peening, contains great potential. For this purpose, the present study deals with the investigation of the effects of plastic deformation in steel material according to increase the hardness as well as to influence the material structure in near-surface regions by the use of an electromagnetic hammer peening device. The deformation-induced processes of an austenitic stainless steel X5CrNi18-10 (1.4301) at room temperature were investigated.

Testing of intergranular and pitting corrosion in sensitized welded joints of austenitic stainless steel

Pitting corrosion resistance and intergranular corrosion of the austenitic stainless steel X5Cr Ni18-10 were tested on the base metal, heat affected zone and weld metal. Testing of pitting corrosion was performed by the potentiodynamic polarization method, while testing of intergranular corrosion was performed by the method of electrochemical potentiokinetic reactivation with double loop. The base metal was completely resistant to intergranular corrosion, while the heat affected zone showed a slight susceptibility to intergranular corrosion. Indicators of pitting corrosion resistance for the weld metal and the base metal were very similar, but their values are significantly higher than the values for the heat affected zone. This was caused by reduction of the chromium concentration in the grain boundary areas in the heat affected zone, even though the carbon content in the examined stainless steel is low (0.04 wt. % C).

Laser-assisted metal spinning for an efficient and flexible processing of challenging materials

The demand for components made from high performance materials like titanium or nickel-based alloys as well as strain-hardening stainless steel is steadily increasing. However, conventional forming operations conducted on these materials are generally very laborious and time-consuming. This is where the limitations of metal spinning also become apparent. Using a laser to apply heat localized to the forming zone during metal spinning facilitates to enhance the formability of a material. In order to analyse the potential of the new manufacturing process, experimental investigations on laser-assisted shear forming and multi-pass metal spinning have been performed with austenitic stainless steel X5CrNi18-10, nickel-based alloy Inconel 718 and titanium grade 2. It could be demonstrated that the formability of these materials can be enhanced by laser-assistance. Besides the resulting enhancement of forming limits for metal spinning of challenging materials, the forming forces were reduced and the product quality was improved significantly.

Testing of susceptibility to intergranular corrosion in welded joints of austenitic stainless steel

The susceptibility to intergranular corrosion of welded joints of austenitic stainless steel X5CrNi18-10 was examined. The testing was performed by the electrochemical potentiokinetic reactivation method with single loop (EPR) and double loop (DL EPR). Also, the susceptibility to intergranular corrosion of stainless steels after senzibilization heat treatment (675 °C/1h) was examined. At given welding parameters (current intensity, the thickness of welded samples of stainless steel, etc.) the base metal is completely resistant to intergranular corrosion, while the heat affected zone shows a relatively low susceptibility to intergranular corrosion. After senzibilization heat treatment the stainless steel showed something higher susceptibility to intergranular corrosion. The advantages of applied electrochemical methods in relation to the classical chemical methods for intergranular corrosion testing were analyzed. DL EPR and EPR methods provide quantitative data on the sensitization degree to intergranular corrosion (in welded joints) and also to intergranular stress corrosion cracking.

Forming a Structured Surface of a New Type of Solar Absorber with Hydroforming

One of the ways to increase efficiency of the solar absorber is modification of absorption area in the system of pyramidal cavities, where the incident radiation is absorbed by multiple reflections. The paper deals with the technology of production of the flow solar absorber with a structured surface in a single technological operation using hydroforming. Two laser-welded sheets are inserted into the forming chamber. Then the space between them is pressurized with hydraulic fluid which causes their form to the desired shape. The first part of this article describes hydroforming device. The second section deals with theoretical simulation of forming a different structured surface in the programming environment of ANSYS. As follows practical test of hydroforming is performed. Austenitic stainless steel X5CrNi18-10 was used as a material for the production of samples.

Experimental Investigation and Analysis of Cutting Forces When Machining X5CrNi18-10 Stainless Steel

In this study, cutting forces experimental measurement an analysis with special carbide insert when turning austenitic stainless steel have been investigated. Stainless steel X5CrNi18-10 is often considered as poorly machinable material. In this experimental study a number of turning tests carried out by using a test lathe and a cutting force measuring device are presented. Accordingly the effect of cutting speed and tool insert cutting geometry on cutting forces in turning austenitic stainless steel X5CrNi18-10 (AISI 304) using Wiper cemented carbide tool insert has been discussed. The effect of cutting parameters (feed rate, depth of cut) is also analyzed by cutting forces measurement. The input parameters were varied as vc = 100 m.min-1, f = 0,150 and 0,275 mm and edge geometry r = 95°, r'= 5°, εr = 80°, rε = 0, 8 mm, s = -6°. The results show that main cutting force Fc decreases with the increasing of cutting speed in turning without using the coolant. A benefit for production process also confirmed fact that this growth is 2,5 to 3 times higher as for turning of CS0E4 under the same machining conditions due to the hardening of austenitic steels for chip creation. It was also noted that experimental specimens showing larger cutting forces then generated worse surface finish as well as larger surface damage.

Investigation of Different Hard Coatings for Micromilling of Austenitic Stainless Steel

(Micro-)Machining of austenitic stainless steel is highly challenging due to the formation of build-up edges, adhesive tool wear and also the ability for work hardening, the low thermal conductivity, and the high toughness. Here, the application of tool coatings is a suitable method to extend tool life and to improve consequently the overall workpiece quality. Yet the qualification of different tool coatings for micromilling austenitic stainless steel has to be analysed.In this investigation micromilling experiments applying two fluted endmills having a diameter of d = 1mm with different hard coatings were applied. The austenitic stainless steel X5CrNi18-10 (1.4301) served as the workpiece material. The tool coatings were CrN, TiN, AlCrN, AlTiN and TiAlN. Using a constant set of cutting parameters and the same basic tool geometry, the achievable performance of the different coatings was evaluated in terms of the process forces, the tool wear and the achievable surface quality. The application of a TiAlN and AlCrN coating generated very good results regarding the tool wear. Relating to the surface quality, the AlTiN coating provided the best results.

Analysis of Micro Burr Formation in Austenitic Stainless Steel X5CrNi18-10

This paper presents the results on the analysis of micro-burr formation for slot milling of austenitic stainless steel X5CrNi18-10. Two-fluted submicron grain cemented carbide tools with a diameter of d = 0.5mm were used. Applying cutting speeds from vc = 100 m/min to vc = 200 m/min and feeds per tooth from fz = 6μm to fz = 8μm the influence of these parameters on the burr formation was investigated. Additionally the effect of the lubrication method – minimum quantity lubrication, flood lubrication and bath lubrication – on the burr formation was analysed.

Cavitation Erosion Resistance of Austenitic Stainless Steel after Glow-Discharge Nitriding Process

This paper presents investigation of cavitation erosion resistance of nitrided austenitic stainless steel X5CrNi18-10. The diffusion layers were produced by using different parameters of reactive atmosphere (N2:H2). The microstructure, chemical composition and phase identification of the modified layer were examined using scanning electron microscopy, glow-discharge optical emission spectrometer and X-ray diffractometry, respectively. Cavitation erosion resistance of produced surface layers was investigated in a rotating disc facility. As a property characterizing the cavitation erosion resistance of manufactured surface layers were proposed incubation period and mass loss after 330 min of cavitation test. It was found that cavitation erosion resistance of modified surface layers is lower than reference material (not treated X5CrNi18-10 stainless steel).

Monitoring laser cut quality using acoustic emission

The paper presents results of an analysis of acoustic-emission (AE) signals obtained during laser cutting of a steel plates, which are frequently used in the production of automotive body components. In the course of laser cutting, continuous signals, which are related to the quality achieved of the laser cut, are measured. After laser cutting characteristic AE bursts in the specimen material, which are results of a thermal influence, can be detected. The presence of dross is an important indicator of poor quality of laser cutting. The investigation on laser cutting was conducted on an unalloyed steel DC04 sheet and on austenitic stainless steel X5CrNi18-10 sheet of 1.5 mm in thickness. The same physical mechanism in the cut formation at both steels, however, resulted in a considerable different cut quality, which was indicated by the AE signals captured after the cutting process.

Wear behaviour of carbon nanotube reinforced epoxy resin composites

This paper deals with the effect of a multi-walled carbon nanotube (MWCNT) reinforcement on the wear behaviour of Epoxy (EP) composites. Firstly, various dispersion methods were compared. Secondly, the optimum CNT amount was evaluated. In a third step, dry lubricants were added to the optimised EP/CNT composite. Finally, the influence of the steel counterpart (martensitic bearing steel 100Cr6 and austenitic stainless steel X5CrNi18-10) was studied. The preparation method was found to have a decisive effect on the wear behaviour of the composite. A pre-treatment of the CNTs in concentrated nitric acid proved beneficial. Even more important was the mixing method. A dual asymmetric centrifuge delivered so good wear results that the pre-treatment could be skipped. The optimum CNT content was at about 1 wt%, regardless of the preparation method. The lowest wear rates were found after addition of 10 wt% graphite. MoS2 proved to be less effective and Polytetrafluorethylene (PTFE) even increased the wear. The wear rates against the unalloyed martensitic steel were far higher than against austenitic stainless steel.