---

In this study a feed forward back propagation artificial neural network (ANN) model was established to predict Vickers microhardness in aluminum-alumina nanocomposites which have been synthesized by mechanical alloying and hot pressing. Volume percent of reinforcement, size of nanoparticles, force in microhardness test; and mechanical alloying parameters, such as time, ball to powder ratio (BPR) and speed of ball mill were used as the inputs and Vickers microhardness as the output of the model. Effective parameters in training such as learning rate, hidden layers and number of neurons, were determined by trail and error due to amount and percentage of errors. Regression analysis in train, validation and test stages; and mean squared error were used to verify the performance of neural network. Average error of predicted results was 2.67% or 2.25 Vickers. Also mean squared error for validation data was 7.76. As can be expected, ANN methods reduce the expenses of experimental investigations, by predicting the optimum parameters.

---

Employing of complex surfaces in different industries such as aerospace and die and mold is increasing. For milling of such surfaces, considering factors such as strategies and machining parameters which affect the machinability is necessary. The objective of this study is to investigate the effect of different strategies and machining parameters on microhardness of a typical curved surface (convex) of stainless steel 1.4903. The cutting tool used in this study was ball nose end mill coated TiN and the strategies employed were Raster, 3D-offset, Spiral and radial. Design of experiments was done using Taguchi method. The input parameters were cutting speed, feed rate and step over. After conducting experiments, surface layers hardness of milled samples were measured. The results showed that various tool paths have different influence on microhardness of milled surfaces. Regardless of cutting condition, surface hardness after machining in all strategies was more than the primary hardness of the workpiece material. Spiral strategy provided the most hardness and radial strategy the least hardness. In addition, increasing the feed rate, cutting speed and step over, rised surface hardness and step over had least influence on hardness. The most hardness magnitude was reported in cutting speed of 180 m/min, feed rate of 0.18 mm/tooth and step over of 0.7 mm which shows 56 % of increase.

---

Hard steels are widely used in automotive industry, molding and production of well drilling bits because of its high wear resistance and strength. The tendency to hard machine of these steels is growing in order to achieve high dimensional and geometrical accuracy, increased productivity and improved workpiece properties. In this research, relation between cutting parameters and final surface integrity in hard milling process of a workpiece made out of 4340 steel while using minimum quantity lubrication system is studied. Different parameters were considered in three levels as main milling parameters including: cutting speed, feed rate, axial and radial depth of cut and consequently the effect of these parameters on surface microhardness and white layer thickness were studied using Response Surface Methodology (RSM). The analysis of variance (ANOVA) showed that a model of quadratic polynomial function would work perfectly in order to estimate microhardness and it can also estimate experimental results while a linear model can evaluate white layer thickness changes, better. Also, Statistical analysis revealed that all cutting parameters increase microhardness and white layer thickness. Feed rate with 73.1% and cutting speed with 14.4% had more effect on microhardness comparatively. White layer thickness also varied between 7.6 μm to 16.1 μm while different cutting conditions were applied and cutting speed with 81.3% and feed rate with 9.4% had the most effects on white layer thickness.

---

Engineering components during service are exposed to destructive phenomena such as wear which may lead to their destruction. For their protection and reduction of costs of replacement of these defective components and also increasing productivity, attention is given to welding processes for depositing a wear-resistant layer on the components. In this research, the effect of welding current on last layer weld quality deposited on carbon steel by shielded metal arc welding process using Fe-based hardfacing electrodes is investigated. The chemical composition of the weld deposit layers was studied by quantometery. Optical and scanning electron microscopes, energy dispersive X-ray fluorescence and X-ray diffraction were used for microstructural studies. Microhardness and pin on disk wear tests were also employed for microhardness and wear resistance evaluations. The metallography and X-ray diffraction results show presence of martensite and retained austenite in the microstructure of the last deposited weld layer. The results of chemical analysis and microhardness and wear-resistant tests show that increasing the current increases weld dilution which leads to reduction of alloying elements affecting hardness and wear resistance of the weld deposit and hence these properties decrease slightly. Evaluation of the worn surfaces shows that the wear mechanism on the last deposited layer is of abrasive wear type.

---

Owing to direct contact with the machined surface, the flank surface can cause unfavorable effects on the surface integrity in high speed milling. Thus, in this study, the influences of flank wear width on the main characteristics of surface integrity like roughness, topography, microhardness and electrochemical corrosion resistance during high speed milling process is investigated. Milling tests were performed under constant cutting conditions with three repetitions and using 12 tools with flank wear widths on the AISI 4340 hardened steel. It was concluded that using the tool with flank wear width up to 0.4 mm increase roughness and microhardness, uniformly (95% for surface roughness and 6.3% for microhardness relative to new tool). However, using a tool with the flank wear of 0.6 mm increases these outputs up to 484% and 18.6%, respectively. Surface topography images also revealed that using the tool with the flank wear width of 0.6 mm can cause irregular forms of material flow on the surface. Using the tool with the flank wear of 0.4 mm or less had an insufficient effect on the in-depth microhardness distribution. In addition, electrochemical impedance spectroscopy of the milled surfaces showed that relative to new tool, using tools with 0.4 and 0.6 mm flank wear, reduce Rcorr up to 22% and 83%, respectively. It indicated lower electrochemical corrosion resistance of milled surfaces with 0.6 mm worn-out tools.

---

In this research, microhardness variations of subsurface in hole making on a AISI4340 steel workpiece was studied experimentally. For this purpose, four hole making methods were used including; helical milling, profile milling, drilling with and without predrilling. The design of experiments utilized full factorial method in which two main cutting parameters including cutting speed (Vc) and feed rate (fz) were changed in three levels. Nine experiments were performed for each process and Hardness variations of substrate layer along the hole radial and axial distances were investigated (216 hardness measurements points). Results showed that the measured hardness in all of the experiments were higher than bulk material hardness, regardless of cutting conditions and the maximum hardness value was found in the upper levels of cutting parameters of traditional drilling method (729 Vickers). In addition, due to workpiece temperature and work hardening increasing with prolongation of the process time, the maximum hardness value was obtained on the exit surface of hole in all processes. Also, least microhardness variations was found when using traditional drilling with predrill which represents superiority of non-continues, multistage hole making processes and conventional drilling using predrill in creation of holes with more uniform properties.

---

In this paper the capability of laser surface hardening of martensitic stainless steel AISI 410 is conducted by using a Nd:YAG pulsed laser with a maximum power of 700 W. Focal point position (22mm to 34mm) and laser pulse energy (14.7J to 16.8J) were considered as process variable parameters. microhardness was measured in depth and surface of hardened layer. Metallography of samples was conducted in order to study the microstructure of hardened zone. Also geometrical dimensions of hardened zone (width and depth), microhandness distributions in depth and width of hardened layer, microstructure of hardened layer were investigated. Results show that by increasing laser pulse energy and decreasing the laser focal point position, the hardness and depth of hardened layer increases. Observations indicated that solid state transformation and carbide solution in steel during laser surface hardening process, improved the surface hardness. Lower delta ferrite in martensitic structure in laser hardened layer lead to higher microhardness. Maximum hardened layer of 350 µm in depth and 2208 µm in width and maximum surface hardness of 747 HV0.3 is obtained in maximum pulse energy of 16.8J.

---

Surface engineering in many manufacturing industries plays an important role in improving product performance and increasing the operating time of parts. Pure aluminum has a very high electrical conductivity, good corrosion resistance and strength to weight ratio. However, due to very low hardness and wear resistance, its application is limited. Therefore, this paper is studied may improve the surface properties of pure aluminum using copper and nickel as alloying elements using electric discharge process. The pulse on time and pulse current as input parameters and surface hardness, alloyed layer texture and surface roughness as output parameters have been considered. According to the microhardness testing results, in this alloying method, the average hardness of the aluminum parts is about more than 8 times and in some parts of the 38.5 Vickers reached up to 450 Vickers, Based on the results of XRD analysis, the formation of intermetallic compounds Al3Ni2, ALCu, and Al4C3 increased surface hardness. The results show that by increasing the pulse on time surface hardness increased and surface roughness becomes greater. Also, Increasing pulse current the surface roughness increasing trend.

---

---

---

---

electrical discharge coating (EDC) is the simplest way to deposit a thin or thick coating on the surface of a substrate to change the properties of this undesirable layer. In the EDC process, the molten pool produced due to sparking in electrical discharge is combined with material particles from the loosely bonded compacted electrode (green compacted) and then rapidly cooled to form a coated layer. Extensive methods for coating the surface of the substrate exist such as electroplating, electroless plating, vapor deposition methods, thermal spraying and many others. These processes have disadvantages such as high capital costs, complexity, higher setup complexity and space requirements that limit their implementation to some extent. Among all coating methods, EDC has advantages over other coating methods. For EDC, there is no need to set up any equipment to create a vacuum or isolation environment around the bed. Also, only by changing the different variables of the machine, the thickness can be changed and the characteristics of the coating layer can be controlled. This study focuses on chrome ceramic coatings formed in the EDC process on stainless steel substrates (ST37) with process parameters with 8 amp current and 100 µs on time. The results showed that the hardness of stainless steel coated with chromium and copper increased to 1284 (HV) in electrical discharge.
 

---

Today, the wire arc additive manufacturing process is based on gas metal arc welding as one of the electric arc fusion processes, widely used in the industry due to its high efficiency. The correct selection of input parameters directly affects the welding quality, and by controlling those parameters, the amount of welding material can be reduced, its properties can be improved, and then the efficiency of the process can be increased. In this research, the production of a composite sample with a combined electrode by gas metal arc welding (GMAW) was investigated. At first, the welding speed, voltage, and wire speed were selected by studying and checking the effective parameters of the process in the wire and arc additive manufacturing (WAAM) by gas metal arc welding. Then, in order to evaluate the effects of effective welding parameters, three three-level factors were designed by the Taguchi method in Minitab software with an L9 array-related experiment. After performing the appearance review process, tensile and microhardness tests were performed. The tensile test results showed that the highest tensile strength is 294.327 MPa in the sample with a welding speed of 86 mm/min, voltage of 32 V, and wire feeding speed of 6 m/min. The microhardness test results showed that the highest value of microhardness was 463.1 Vickers for the sample produced with a welding speed of 86 mm/min, voltage of 27 V, and wire feeding speed of 5 m/min.

---

 The conventional material removal processes have always run into difficulties in machining hard materials, and nickel-based superalloys are no exception. The inherent properties of these materials usually lead to high tool wear rates and low surface integrity. These concerns justify the need for combining conventional material removal processes with advanced technologies. Laser Assisted Machining is one such process by which, through localized softening of work material prior to the cutting operation, a more efficient material removal process can be realized compared with what can be done by conventional machining. This work studies the effect of machining parameters such as constant Rotational speed at 400 RPM, feed rates of 0.035, 0.07, 0.105 mm/rev, and cutting depths of 0.3, 0.6, and 0.9 mm on variation of cutting force, chip temperature, surface roughness, and microhardness in variation of the workpiece surface. The process is a Laser Assisted Turning (LAT) process compared to conventional Turning (CT) by analyzing the parameters for a Waspaloy. A fiber laser with constant power output of 500 W was used to irradiate the tool material. The angle of contact of the beam with the tip of the tool was fixed at 60°. The workpiece's hardness was 385 ± 10 Vickers initially and had a diameter of 25 mm. It has been revealed that the application of LAT decreases the cutting force up to 16% compared to CT. The workpiece surfaces produced by LAT had higher chip temperatures than CT and were of 42% better quality in terms of surface roughness. In the LAT process, the difference in microhardness values at different points on the workpiece surface was within a much smaller range than in the CT process. The results showed that as the scanning speed of the laser increased on the surface of the workpiece, the thickness of the laser heat-affected zone below the surface of the workpiece decreased.