Plasma spray of nicraly coating on laser surface modified H13 tool steel

This thesis presents experimental study of nickel-based alloy, NiCrAlY coating on laser modified AISI H13 steel using atmospheric plasma spray (APS). AISI H13 steel is often being used as die material in metal forming technology, specifically semi solid metal processing. Repetitive process of incoming high temperature, solidification and rapidly quenched semi solid metal through die, causes erosion and corrosion wear on the die cavity surface. Erosion which was causes by friction and corrosion by chemical reaction mitigate die performance and durability properties. Hence, retaining die properties were crucial to gain optimum semi solid metal processes. This study aims to modify AISI H13 steel substrate surface for enhanced mechanical properties and interfacial bonding with NiCrAlY coating. Mechanical properties of AISI H13 steel surface micro hardness was enhanced from rapid quenching process by pulse laser surface modification. While, interfacial bonding of NiCrAlY coating was enhanced by increasing the percentage of chemical elemental diffusion and the surface roughness asperities for mechanical interlocking. A modified layer of AISI H13 steel with enhanced surface properties was developed using two different laser spot size of 90 µm and 600 µm separately. The mechanical properties and interfacial bonding of NiCrAlY coating on laser surface modified AISI H13 steel substrate were enhanced at different laser parameters. Laser parameters of 90 um spot size used were laser peak power; 0.76 kW and 1.3 kW, pulse rate frequency (PRF); 2500 Hz and 2800 Hz and laser scanning speed; 2.0 mm/s and 6.0 mm/s. While, laser parameters of 600 um spot size used were laser peak power; 1.6 kW and 2.0 kW, pulse rate frequency (PRF); 40 Hz and 60 Hz and laser scanning speed; 14.13 mm/s and 20 mm/s. Prior to NiCrAlY coating, lasered samples being modified by 600 um laser spot size went on sandblasting process. Surface profile such as asperities, valleys depth and peak height and average roughness, Ra also had been analyzed. Asperities at the entire surface profile with low peaks and valleys size promotes wettability of coating particle splats during coating. Elemental analysis showed chemical bonding occurred in coating because of element diffusion. Metastable phase occurred on the laser modified surface inspired atomic diffusion that enhanced coating adhesion. Metastable phase consists of excited energy that promotes atomic diffusion between the laser modified/coating interlayer. Results for coating interfacial toughness obtained by Vickers interfacial indentation test (IIT) were obtained above reference sample toughness measurement which was 2.08 MPa. Interfacial toughness range between 2.02 to 6.54 MPa. For conclusion, interface bonding of NiCrAlY coating is enhanced based from the research objectives. Mechanical interlocking plays an important role for interface bonding of NiCrAlY coating. Surface that contains asperities at whole surface profile, decreasing depth and peaks measurement increased coating adhesion. For atomic bonding, metastable α-Fe phase occurs from laser surface modification assists atomic diffusion in the NiCrAlY coating interlayer. Mechanical interlocking plays major role in the succesful of the NiCrAlY coating adhesion. Hence, NiCrAlY coating on laser modified H13 steel by 600 um laser spot size requires surface post processing using sandblasting. This research findings were important to obtained achievement of coating layer with resistance to erosion and corrosion in the direction of manufacturing sustainability

Optimization of EDM Injection Flushing Type Control Parameters Using Grey Relational Analysis on AISI 304 Stainless Steel Workpiece

This paper deals with optimization of Electrical Discharge Machining (EDM) Injection flushing type control parameters on multi-performance optimization characteristics instead of single performance optimization using Grey Relational Analysis (GRA) Method. The experimental control parameters were being optimized according to their various machining characteristics namely material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR) using copper as the tool and AISI 304 stainless steel as the workpiece. This parameters optimization was based on Taguchi’s orthogonal array (OA) combined with GRA. A grey relational grade (GRG) calculated based on GRA was used to optimize the EDM process with multiple performance characteristics and Taguchi’s L18 OA was used to plan the experiments. The machining parameters selected are polarity, pulse on duration, discharge current, discharge voltage, machining depth, machining diameter and dielectric liquid pressure. Results shown that machining performance was improved effectively using this approach. The predicted responses at optimum parameter levels are in good agreement with the results of confirmation experiments conducted for verification tests

LITERATURE REVIEW OF OPTIMIZATION TECHNIQUES FOR CHATTER SUPPRESSION IN MACHINING

Chatter produces a poor surface finish, high tool wear, and can even damage machine tools because of the regenerative effect, the loss of contact effect, and the mode coupling effect. Various research works have investigated the suppression of chatter by either passive or active methods, such as by applying absorbers, damping, varied speeds and other alternatives. In this paper, it can be observed that for chatter suppression, optimization focuses on spindle design, tool path, cutting process, and variable pitch. Various algorithms can be applied in the optimization of machining problems; however, Differential Evolution is the most appropriate for use in chatter suppression, being less time consuming, locally optimal, and more robust than both Genetic Algorithms, despite their wide applications, and Sequential Quadratic Programming, which is a famous conventional algorithm

Assessment Method for Course Outcome and Program Outcome In Outcome Based Education (OBE)

Abstract—Outcome Based Education (OBE) has become the standard of practice in Higher Education Institutions especially those that offer programs in engineering. This paper introduces a method to measure students’ performance in respect to OBE concept. The flow of measurement is taken from students’ progress marks and also final exam. The marks are then converted whether they meet the course outcome set by instructor. After getting the course outcome score, contribution of each course to program outcome can be measured progressively until students complete their 4 year program. In getting the score Program Outcome, the instructor would plan earlier on the assessment question specification to program outcome. The method is found to be very practical to be implemented for any instructor to measure the course outcome and program outcome. In addition, it would contribute to the continuous quality improvement process as specified by Washington Accord as well as Engineering Accreditation Council, Malaysia

Literature Review of Optimization Techniques for Chatter Suppression In Machining

Chatter produces a poor surface finish, high tool wear, and can even damage machine tools because of the regenerative effect, the loss of contact effect, and the mode coupling effect. Various research works have investigated the suppression of chatter by either passive or active methods, such as by applying absorbers, damping, varied speeds and other alternatives. In this paper, it can be observed that for chatter suppression, optimization focuses on spindle design, tool path, cutting process, and variable pitch. Various algorithms can be applied in the optimization of machining problems; however, Differential Evolution is the most appropriate for use in chatter suppression, being less time consuming, locally optimal, and more robust than both Genetic Algorithms, despite their wide applications, and Sequential Quadratic Programming, which is a famous conventional algorithm

An Investigation of Phase Crystallinity in Laser Modified Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coating

This paper presents laser surface modification process of plasma sprayed yttria stabilized zirconia (YSZ) thermal barrier coating (TBC) for enhanced hardness properties and low surface roughness. A 300W JK300HPS Nd: YAG laser was used to process YSZ TBC sample surface. The parameters selected for examination were laser power, pulse repetition frequency (PRF) and residence time. Micrographs of the TBC system were captured using EVO 15 Scanning Electron Microscope (SEM). Surface roughness was measured using 2-dimensional stylus profilometer. X-ray diffraction analysis (XRD) was conducted to measure phase crystallinity of the laser-modified coating surface. X-ray diffraction patterns were recorded in the 2θ range of 10 to 80° using Bruker D8 Advance system with 0.7Å wavelength from a copper source (~1.5Å). The laser modified surface exhibited higher crystallinity compared to the as-sprayed samples. The presence of tetragonal phase was detected in the as-sprayed and laser processed samples. The hardness properties of laser modified TBC increased 15% of the as-sprayed sample. These finding are significant to development of thermal barrier coating design optimization for enhanced surface properties of semi-solid forming die

Study of the Surface Integrity of AISI 4140 Steel in Wire Electrical Discharge Machining

he Wire Electro Discharge Machining (WEDM) process is a violent thermal process where literally thousands of electrical discharges are produced in a fraction of a second in order to erode a certain volume of metal. The process is most used in situations where intricate complex shapes need to be machined in very hard materials (such as hardened tool steel). However, the process generates surface that have poor properties such as high tensile residual stresses, high surface roughness, presence of micro-cracks and micro-voids. These properties vary with different levels of the main machining parameters. The aim of this paper is to present experimental work that has been done in order to quantify the effect of some of the main WEDM parameters on the surface texture of AISI 4140 steel. 2D surface measurements were taken on all WEDM samples and 2D surface characterization has been carried out in order to calculate the different surface texture parameters. In this work, the surface characteristics caused by WEDM were analyzed by Scanning Electron Microscopy (SEM)

Effects Of Polarity Parameter On Machining Of Tool Steel Workpiece Using Electrical Discharge Machining

Electrical discharge machining (EDM) has been recognized as an efficient production method for precision machining of electrically conducting hardened materials. This research studies the effect of polarity on the material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR) of the tool steel work piece machining using EDM. Design of experiments (DOE) using L18 orthogonal arrays were being selected and the results being represents using response graph. Wrong polarity can have significant implications on speed, wear, and stability and to investigate this phenomenon using L18 orthogonal arrays design of experiment. The optimum parameters and the effects of polarity to the material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR) are being discussed

Effect of Different Cooling Rates Condition on Thermal Profile and Microstructure of Aluminium 6061

Thermal analysis and microstructure characterization provide information regarding material thermal profiles and microstructure formation. Wrought aluminium alloys offer significant advantages in terms of higher ultimate tensile strength (UTS) and yield strength but relatively poor fluidity properties. The objective of this experiment presented in this paper was to understand the relationship between solidification rate, metallurgical behaviour, and fraction phase growth of wrought aluminium 6061. This information was crucial and important to the foundry industry to understand the material behaviour that will help to cast wrought aluminium 6061. Thermal analysis and microstructure of wrought aluminium 6061 on different cooling conditions are present in this paper. In this work, Aluminium 6061 heated and melted in a graphite crucible at a temperature of 800 °C. Two thermocouples located at the centre and 20 mm from the graphite crucible wall. Slow cooling rate condition experiment rig was developed by placing graphite crucible into a chamber with kaowool insulation. Normal cooling rate condition was developed by allowing the molten solidify at room temperature. Fast cooling rate condition was prepared by applying a forced airflow over the graphite crucible. The slow, normal, and high cooling rates were calculated at 0.03 °C/s, 0.2 °C/s and 0.3 °C/s respectively. Cooling curve analysis was performed to predict various areas of solidification phase and fraction solid. In Addition, the microstructure formation was observed, recorded, and compared between different cooling conditions. The results show slow cooling rate condition formation of eutectic and solidus temperatures occurred far from liquidus temperature. The eutectic and solidus temperature was increased with the increment of the cooling rate. Furthermore, the DCP temperature of slow cooling rate condition at 638.3 °C was the lowest while gives wider temperature range corresponding to the fraction solid percentage increment. Meanwhile, an increase in cooling rate refined the microstructure, improved the grain circularity and at the same time reduced the aspect ratio