Patthi Hussain

A Review of Friction Stir Welding Pin Profile

Friction stir welding (FSW) is a solid state joining process where the joint occurs below the melting point of the base metal. Recently, not only soft materials but also high melting materials have been given an attention in FSW research activities. There are many studies on high melting materials such as steel, titanium, and inconel. There are different parameters which contribute to the joint quality. Many researchers have studied on the traverse and rotational speeds as the main process parameters in order to obtain optimum weld quality. Tool geometry is another important parameter that has an influence on the weld quality. This paper aims to review the development of various pin profiles and its effects to the microstructure and mechanical properties of the weld joint. Based on the published papers, square pin profile produced sound joints. However, in other studies threaded cylinder or threaded taper provides better joints. Above all, there is an equal result among all studies in which threaded shapes are most effective on tool performance.

Microstructure and Nanoindentation Characterization of Low Temperature Hybrid Treated layer on Austenitic Stainless Steel

In this work, the hybrid treated layer on austenitic AISI 316L stainless steels were characterized to investigate the improvement on its surface properties. Characterization of this resulting layer was performed by FESEM (Field Emission Scanning Electron Microscope), USPM (Universal Scanning Probe Microscope) and nanoindentation. By using these methods, changes in the mechanical properties due to the diffusion of carbon and nitrogen at low temperature treatments have been traced. This hybrid treated sample has confirmed a considerable increase in hardness and a small rise in the elastic modulus compared to the untreated sample. It is found that all treated samples have enhance E/H ratio which exhibited the decreasing tendency to plastic deformation and reduced the mismatch of properties, while keeping deformation within the elastic range.

The Effect of Pin Profiles and Process Parameters on Temperature and Tensile Strength in Friction Stir Welding of AL6061 Alloy

The main source of the heat generation during the Friction Stir Welding (FSW) is the friction force between tool and workpiece and the plastic deformation. The geometry of the tool including the pin and the shoulder highly affects the friction force. In this study, the effects of different pin profiles with different rotational and traversing speed are evaluated in order to obtain the optimum pin profile using heat generation and tensile strength. Three different rotational speed and welding speeds are applied with threaded cylindrical, conical, stepped conical and square pin profiles. Thermocouples K type have been embedded in order to record the temperature during the welding at the advancing and the retreating side. Moreover, tensile test and microstructure analysis are performed in order to study the microstructure. The results of experimental process and design of experiments are correlated well. The better joint produced with threaded cylindrical tool pin profile with rotation speed of 1600 rpm and welding speed of 40 mm/min.

The Influence of Nitrogen on The Wear Resistance of Ferritic Stainless Steel

Ferritic stainless steel has low properties of wear resistance and hardness. Normal heat treatment on AISI 430 Ferritic Stainless Steel cannot be treated utilised to achieve this task. However, it can be treated through nitriding method. Nitrogen is well known to improve mechanical, wear and corrosion resistance of stainless steels. Normal heat treatment on AISI Ferritic Stainless Steel is not suitable to achieve this task. Thus, the aim of this work is to investigate the influence of nitriding on wear resistance properties of AISI 430 Ferritic Stainless Steel. The influence of nitriding on the steel were observed. Microstructures, hardness test and scratch resistance analysis for wear resistance were conducted and analysed. Nitriding was carried out at 1200°C for 1 h, 3 h and 5h using nitrogen gas as a medium. Martensitic transformation from ferrite was observed on the as-received samples. From microstructure observations, the influence of nitriding also could be seen. Martensite structure shows higher hardness compare to ferrite structure. Therefore, the hardness for 5 h nitrided sample is higher than 1 and 3 h nitrided sample as more martensite structures was formed at 5 h nitrided sample. Scratch resistance was conducted to analyse the influence of nitriding for wear resistance properties. The depth of penetration obtained shows how much improvement on tribology properties are made. Results from testing conducted shows that the improvement of wear resistance properties is dependent on nitriding time. The longer the nitriding time, the more nitrogen is diffused into the sample. As more nitrogen atoms diffused into the steel, improvement on wear resistance properties are higher.

Nitriding of Duplex Stainless Steel for Reduction Corrosion and Wear

Duplex stainless steel (DSS) which has a dual nature of ferrite and austenite with nearly equal ratio has found a good application in oil and gas industries because of its excellent corrosion resistance, high yield strength, good weldability, and relative low life cycle costing from reduced operating cost. Dual phases of DSS or combination of two-phase existence to be more characterize with better mechanical properties than a single-phase metal of ferrite or austenite. Nitrogen is a good strengthening alloy for DSS because it forms a solid solution of (Fe, Cr)2N which is responsible for the hardness and wear resistance in DSS. Spontaneous formation of oxide or passivated layer is responsible for shield and direct exposure of surface of stainless steel to corrosive medium though is susceptible to depletion and deterioration in high chlorine water and low pH level in production environment. Total damage of passivated region on the surface of DSS prompts initiation of localized defect such as pit which grows over a time to form crack. Oil and gas environment is characterized with high H2S content which is a constraint in application of DSS in this environment because of its insignificant resistance to sulfide stress corrosion cracking (SSCC) and hydrogen-induced cracking (HIC).

Surface characteristics of low temperature hybrid thermochemical treatment of AISI 316L

This investigation proposed the low temperature thermochemical treatments in conventional tube furnace of hybrid treating which introduces nitrogen and carbon simultaneously with the aim to improve surface properties of AISI 316L. The outcome of the work showed the formation expanded austenite structured which is supersaturated with nitrogen and carbon. This structure is responsible to the higher hardness as well as better wear property without impairing its corrosion resistance. Characterization of this expanded austenite layers were performed including FESEM, USPM and elemental analysis to reveal the characters of the produced thin layers. Elemental profile of nitrogen and carbon across the hybrid treated layer were obtained by EDS-SEM. The results also demonstrate that hybrid treatment produces a thicker and unique layer on higher temperature treatments for 450°C without impairing its corrosion resistance according to the absence of nitride and carbide of treated layers.

Morphology, topography, and hardness of diffusion bonded sialon to AISI 420 at different bonding time

Sialon and AISI 420 martensitic stainless steel were diffusion bonded in order to study the effect of bonding time on reaction layer’s growth. Joining of these materials was conducted at 1200°C under a uniaxial pressure of 17 MPa in a vacuum ranging from 5.0 to 8.0×10−6 Torr with bonding time varied for 0.5, 2, and 3 h. Thicker reaction layer was formed in longer bonded sample since the elements from sialon could diffuse further into the steel. Sialon retained its microstructure but it was affected at the initial contact with the steel to form the new interface layer. Diffusion layer grew toward the steel and it was segregated with the parent steel as a result of the difference in properties between these regions. The segregation formed a stream-like structure and its depth decreased when the bonding time was increased. The microstructure of the steel transformed into large grain size with precipitates. Prolonging the bonding time produced more precipitates in the steel and reduced the steel thickness as ...

Nanoindentation and microstructure of hybrid treated of AISI 316L at low temperature

This paper presents the characterisation of hybrid treated layer on austenitic AISI 316L stainless steels using field emission scanning electron microscope (FESEM), universal scanning probe microscope (USPM) and nanoindentation after low temperature thermochemical treatments. By using these methods, the improvement of its mechanical properties due to the diffusion of carbon and nitrogen at low temperature treatments were confirmed. The hybrid treated layer has shown increment of hardness and elastic modulus compared to untreated sample. Based on the investigation, it is shown that all treated samples have enhanced E/H ratio which demonstrated the decreasing tendency to plastic deformation and reduced the disparity of properties, while keeping deformation within the elastic range.

Effect of Nitriding on Reaction Layer of Diffusion Bonded Sialon to AISI 420 Martensitic Stainless Steel

Joining sialon to as-received and nitrided AISI 420 martensitic stainless steels using diffusion bonding is reported in this paper. The samples were joined at 1200°C for one hour under uniaxial pressure of 17 MPa in a vacuum (1x10-5 Torr). After joining process, the microstructure, interdiffusion of elements, and hardness of the joint were studied. The interdiffusion and reactivity of the elements created the reaction layer. It consisted of interface layer on the sialon side whereas thicker diffusion layer was formed on the steel side. Thinner reaction layers were observed in joining sialon to nitrided steels compared to joining sialon to as-received steel due to less reactivity between the joined materials. However, more precipitates such as carbides were formed in the parent steel with longer nitriding time. Gaps were formed between the diffusion layer and the parent steel but the interfacial bonds were strong since no cracking occurred on the samples. Since the reaction layer had intermediate hardness, it contributed to the joint’s ductility that reduced the effect of thermal expansion mismatch between the joined materials by acting as a shock absorbing zone.

Precursor preparation for Ti-Al-V-Y alloy via FFC cambridge process

This paper presents the work done for the preparation of precursor for producing Ti-Al-V-Y alloy via FFC Cambridge process. The aim of the work is also to investigate the uniformity of the phases formed during the pre-processing of the precursor.The importance of the alloy for mechanical and medical applications is well known. Titanium oxide (TiO2), vanadium oxide (V2O5), aluminium oxide (Al2O3) and yttrium oxide (Y2O3) were selected as raw materials for precursor. The expected composition for the new alloy is Ti-6Al-4V-0.5Y. Water was used as a binder for the precursor. The materials were pre-mixed by ball milling for 24 hours and pressed using 13 mm die. The pressed mixtures were then sintered in the furnace at 900°C for 24 hours. The sintered samples were analysed using the optical microscope, electron micrograph with EDX and XRD. The result of the optical micrograph showed that the raw materials were uniformly mixed and well distributed with the presence of porosities. Electron micrograph further verified the morphology of the materials and the elements distribution in the precursor. The overlapping of yttrium and vanadium, Y(VO4) was observed and verified by XRD. The derived formulated precursor was then ready for further work of reduction to Ti-Al-V-Y alloy using FFC Cambridge process.