Application of Taguchi method in optimizing the microstructure of 316LN austenitic stainless steel

The hot deformation behavior of AISI 316LN austenitic stainless steel was studied through isothermal hot deformation tests conducted on Gleeble 1500 thermo‐simulation machine. By using Taguchi method with an L16 (4³) orthogonal array, the hot deformation conditions including deformation temperature, strain rate and strain were optimized for obtaining minimum mean grain size of the steel. Analysis of variance was used for determining the effect of the hot deformation parameters on the mean grain size. The results suggested that the strain had the most significant effect on the mean grain size among the three factors. The percent contributions of deformation temperature, strain rate and strain to the mean grain size were 0.80 %, 2.45 % and 93.32 %, respectively. Finally, the confirmation experiment under the optimum conditions, i.e., 1050 °C temperature, 0.01 s^–1 strain rate and 0.7 strain was carried out. The observational mean grain size (11.4 μm) is approximately twelve times smaller than that of the initial microstructure.     

Effect of rare earth cerium on the impact toughness,corrosion and wear resistance of CrNiMnMo alloyed lining steel

The effects of the addition of rare earth cerium on the impact corrosion and wear resistance of CrNiMnMo alloyed lining steel were studied using metallurgical microscopy, scanning electron microscope, x-ray powder diffraction, a hardness tester, an impact tester, and an impact corrosion abrasion tester. The properties of CrNiMnMo alloyed lining steel with the addition of cerium were compared with that of CrNiMnMo steel without the addition of cerium after being heat treated by same processes. The results show that CrNiMnMo alloyed lining steel with the addition of rare earth cerium consisted of lath martensite with a low residual austenite phase after being quenched and tempered. The lath of the martensite was fine and uniform. The impact toughness and the corrosion resistance of the steel lining board improved greatly with the addition of cerium and the impact toughness increased by 22 % with the fracture mode of being ductile. The CrNiMnMo alloyed lining steel with cerium showed the highest resistance to impact corrosion abrasion compared with the alloy without cerium.     

Challenges in dissimilar friction stir welding of aluminum 5052 and 304 stainless steel alloys

In this study, dissimilar friction stir welding of aluminum 5052 and stainless steel 304 has been carried out with different process parameters. This investigation provides a better insight regarding the defect formation of the weld joints with tilt angles ranging from 0 ° to 2.5 °. The experiments were conducted according to Taguchi L9 orthogonal array by changing the tool rotational speed, and welding speed. The tool pin was kept 70 % towards the aluminum with the tool rotational speed ranging from 800 min⁻¹ to 1200 min⁻¹ with a varying traverse speed of 5 mm/min to 15 mm/min. The bottom part of the stir zone was perfectly welded without any defects. Tunnel defect was detected just above the bottom welded surface. Microstructural analysis reveals that the weld between both materials is formed on the retreating side, whereas on the advancing side, the weld was formed with void defects. Mostly, the stir zone is filled with irregular shaped aluminum and steel parts which were detached from the base material. Several other defects such as voids, cracks, and fragmental defects were observed in the stir zone irrespective of the process parameters. It was observed from the experimental investigations that the tunnel defect can be reduced by increasing the tilt angle.     

Analysis of powder steel material,laser sintering technology and machining on surface parameters and fatigue

The technology of selective laser melting (SLM) is booming in all engineering applications today and tends to expand production of statically and dynamically loaded parts, not only for the prototypes but also for direct metal end–use parts. However, apart from design and type of loading, there still is a number of real material and technological parameters that contribute to the final quality of the produced parts and affect or improve the surface integrity and life of the parts. This paper expands the results and conclusions made in some previous works and presents all data from the tests expressed in their technological relations. The main conclusion is that a suitable machining process did not affect the surface integrity and fatigue of the tested samples, and the key role in assessments were the material structure, its homogeneity and defects.     

Dry machining characteristics of coated inserts and multi response optimization through DEAR-Taguchi method

The primary intent of the proposed research work is to investigate the effectiveness of the titanium aluminium nitride/tungsten carbide-carbide coated insert during dry turning structural stainless steel. The aim of the study is to simultaneously optimise machining variables like spindle speed, depth of cut and feed for several responses like flank wear, material removal rate and surface roughness. Titanium aluminium nitride/tungsten carbide-carbide is coated on the surface of carbide tool by cathodic arc evaporation method. The characterization studies have been conducted to ensure the existence of coating material. Micro hardness of coated and pure inserts was tested, which confirms that titanium aluminium nitride/tungsten carbide-carbide coated insert possesses 17.43 % augmented hardness over pure inserts. The machining was performed by adopting Taguchi experimental design. A multi-response optimization approach was applied in this study that included ranking methodology based on data development analysis and Taguchi's design. The performance index for multiple responses was measured and mathematically analysed for their effect on processing parameters. The combination of parameter such as spindle speed: 2000 min⁻¹; cutting depth: 0.45 mm and feed rate: 0.16 mm rev⁻¹ was experimental as optimal machining parameters.     

Electrochemical performance and microstructural evolution of laser deposited Al‐Sn coating in acidic environment

Outstanding performance of materials is one of the requirements of modifying the existing materials in order to meet a global demand necessary in technology innovation. Direct laser metal deposition technique due to excellent properties has replaced conventional techniques in modifying the surface of materials. The interplay between melting, fusion and optimised laser parameters are very important factors to be considered when using laser metal deposition technique. ASTM A29 steel property was enhanced through this technique by Al‐Sn reinforcements. A 3‐kW continuous wave ytterbium laser system was employed by this process. This research investigated the microstructure and corrosion properties of fabricated laser metal deposited ASTM A29 steel. The resulting microstructure and content of the inconsequential elements in the coatings fabricated were studied to obtain the results achieved. Observation of the microstructure showed typical phase of acicular α′‐martensite attributed to rapid cooling of the molten pool. The electrochemical behaviour was investigated in 1 M HCl solution at 27 °C via potentiodynamic polarization technique. The fabricated coatings had corrosion rate of 0.03435 mm/yr, current density of 3.95 ? 10^?6 A/cm², and polarization resistance of 7093.4 Ω ? cm². While the control had corrosion rate of 16.308 mm/yr and polarization resistance of 8.0631 Ω ? cm².     

Experimental and analytical study of residual stresses relaxation in nitrided 42CrMo4 parts

Initial compressive residual stresses, induced by ionic nitriding treatments, relax during component operating life and it is important to consider the relaxation phenomenon in the design of the component. The paper presents three analytical models (Seungho Han et al., Zaroog and Kodama) to estimate the level of residual stress after cyclic loading. The initial and final residual stresses has been measured after each loading cycle for many load magnitudes using x‐ray diffraction. It was found that about 40 %–50 % of the maximum residual stresses are relaxed during the first cycle. The reduction in the residual stress, are dependent on the applied load because of the plastic deformation caused by the superposition between the nitrided residual stress and the applied load. It was found that the estimated average values by analytical models are comparable with the results of experimental studies after cyclic loading.     

Experimental testing of wood‐concrete and steel‐concrete composite elements in comparison with numerical testing

The paper presents the results of experimental tests with a numerical comparison of some typical composite element systems. Two different kinds of elements were tested: composite steel‐concrete and composite wood‐concrete elements. Deflections at midspan under monotonously increasing static load on simply supported beams were measured. The affects of different types of composite connections on the results were researched. In numerical tests the structure was modeled with two‐dimensional plane elements. The composite surface was modeled with two‐dimensional contact (interface) elements for the continuous connection simulation and modified beam elements for the discrete connection simulation. The applied material models include the most important nonlinear effects of concrete, steel and wood behavior, as well as the nonlinear behavior of the composite surface at the connection. The achieved results of the developed numerical model were compared with the results obtained through the experimental test.     

Scale‐dependent hierarchy of structural elements in the microstructure of thermomechanical treated ferritic steels with residual austenite

Experimental results of the structural investigations of dislocations and carbides are presented here for four steels with ferritic‐carbide structures which were subjected to different final thermal processing. The investigation was carried out using different methods which involved optical microscopy, REM, TEM and x‐ray structural analysis. The complex procedures implemented permitted both investigations at intervals from the macro to the micro scale as well as detection of the total spectrum of the scale and structure levels which form during the steel's thermal treatment. As a consequence of these analyses, representative structural volume elements (RSVE) were detected which includes all relevant structural parameters, i.e. dislocation structures, precipitates and phases.