Microstructural Evolution and Characterization of Inertia Friction Welded Powder Metallurgy Nickel-Based Superalloys
DECEMBER 2017
ABSTRACT
The demand for greater fuel efficiency is continuously increasing in the aerospace industry as is the need to improve thrust by operating at higher temperatures. Novel Ni- based superalloy, RR1000, is a prime candidate for turbine discs, having a substantial amount of stable, ordered L12 intermetallic phase, 𝛾′ (Ni3(Al, Ti)). It is well understood that joining Ni-based superalloys is rather difficult, thus, solid-state welding process such as IFW is of great consideration, as it shows promise in reducing and/or eliminating detrimental effects such as constitutional liquation, strain-age cracking and/or microfissuring.
This paper has aimed to characterize the microstructural features of parent and welded microstructure of IFW ATI RR1000 – SMC RR1000 weldment. It was found that, although RR1000 was manufactured by two different manufacturers, the parent microstructure was essentially the same, having slight differences in grain size yet quite similar microhardness values. Through SEM EBSD analysis, it was found at the edge of the HAZ, located 1.5mm from the WL, was the highest amount of residual strain and greatest % frequency of deformation twins and CSL boundaries, occurring as a result of dynamic recrystallization within the HAZ. Within the HAZ, an absence of primary and secondary 𝛾′ was evident; however, very fine precipitated 𝛾′ was observed. The center of the WL yielded the largest grain size and peak microhardness, a value of 507.33HV. Within the WL area, multiple sites of liquation was evident, with constitutional liquation seen along the grain boundaries, liquid film and relatively large areas of resolidified 𝛾/𝛾′ eutectic product.
Failure Analysis Investigation of Bearing Cap on a Piston Connecting Rod
JANUARY 2017
Abstract—A bearing cap on a piston connecting rod failed while in service which led to a failure analysis investigation. Metallographic analysis revealed a microstructure of pearlite in a proeutectoid ferrite matrix along with manganese sulfide inclusions and carbides present throughout. Fractographic analysis of the failed specimen showed classic brittle fracture, evidenced by secondary cracking, transgranular cleavage and river patterns. Brittle fracture of the bearing cap is believed to be caused by the underlying manufacturing method of intentionally fracturing the bearing cap bolt mating surfaces, as they are sites of high stress concentration.
Keywords—Non Destructive Examination, Optical Microscopy, Scanning Electron Microscopy, Fractography, Secondary Transgranular Cracking, Transgranular Cleavage, River Patterns, Brittle Fracture
Laser Design Optimization
MAY 2017
Abstract—An investigation on a laser housing design was carried out to optimize the design and performance. The initial CAD geometry was provided by the client and a base design simulation was
carried out for analysis of the design’s initial performance. Further simulations were run on the initial design to determine the driving factors which affected the temperature(s) of the system. From this, 4 laser housing designs were created and simulated with an increase in heat source with a combination of alteration to the air and water velocity to meet the client’s constraints. It was evidenced that Laser Housing Design 2 and 4 were the optimized design(s), maintaining a maximum temperature of Helium within ±𝟏% of 220°C, maximum temperature of Aluminum below 45°C, and a maximum water temperature of less than 100°C. Although the 2 designs labeled as optimized designs, it is recommended that Laser Housing Design 2 be used for the laser housing design due to the complexities and limitations of Laser Housing Design 4. This investigation provided a greater insight into the role of simulation in the engineering design process.
Additive Manufacturing
Density and Porosity in SLM TI-6Al-4V
MAY 2017
Abstract—Selective laser melting is an additive manufacturing technique which has become increasingly popular in the production of large scale, net shape components. Because of this growing interest, much research for use of different materials is required. Titanium alloys, Ti6Al4V, is a lightweight and temperature resistant material that is used in aerospace applications. Through the use of SLM manufacturing, physical and mechanical properties are currently being investigated for the future application of SLM in aerospace components. Densification curves of Ti6Al4V were created to understand the relationship between density, porosity and laser energy input. It was observed that lower point distance(s) and smaller hatch spacing yielded an increase in density. Similarly, at higher laser energies, porosity was minimized, thus, density was optimized. The densification curve of Ti6Al4V yielded comparable results to published densification curves, depicting trends of increase in density at higher laser energy inputs. Optimized parameters were selected based on energy input, density and porosity values; as a result, a point distance of 100𝛍𝐦 with a corresponding hatch spacing of 150𝛍𝐦 and a laser energy input of 55.55 J/mm^3 will produce optimized density of Ti6Al4V SLM parts.
Polymers: Property and Design
Use of Polycarbonate in Medical Applications
APRIL 2017
Polymers in the medical industry is rapidly increasing due to the rapid manufacturing and low cost production of reliable products for uses in various medical applications [1]. Thermoplastics are a class of polymer that are used in medical applications; it can be easily shaped above a specific temperature and solidify upon cooling which allows for intricate shapes commonly used in the medical field. This study will thoroughly analyze all aspects of a plastic part of a medical device to be manufactured for use in industry. The plastic part takes form of a closed cylinder which is internally pressurized via a liquid, approximately 887kPa. The length of the cylinder is 10cm long and has a diameter of 4cm. The plastic cylinder must be transparent and undergo manufacturing by means of injection molding. The device will require temperature resistance greater than 120°C to undergo sterilization. The life of the component is desired to be 2 years where it will be under a constant internal liquid pressure of 37°C. The material preferred by the client is polycarbonate; this investigation will determine the potential of polycarbonate as part of this medical device.
Feasibility Report
Creation of an Inter-campus Transport System between the Bay Campus and the Singleton Campus (incl. Student Village)
SEPTEMBER 2016
EXECUTIVE SUMMARY
Following the recent campus developments at Swansea University and further reductions in student loans, the demand for a low cost inter-campus transport system is becoming increasingly significant. This feasibility study investigates the prospect of implementing a not-for-profit, all-electric bus service, between Hendrefoilan Student Village, Singleton Campus and Bay Campus. This service is intended for exclusive use by the students and staff of Swansea University.
Assessment of potential and current transportation options in Swansea highlights a clear gap in the market for an environmentally friendly student transportation method; potentially bringing benefits to the University such as reduced travel costs to students and staff, reduced carbon footprint as well as an association with a revolutionary service in Welsh transportation.
The recommendations discussed in the report include an implementation strategy based on:
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- A fleet of 6 Volvo 7900 Electric Buses.
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- A 16-week implementation time.
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- An estimate investment of £3.7m.
BioBuild - The Circular Economy
NOVEMBER 2016
Executive Summary – A circular economy is a cycle which keeps resources continuously circulating through the entire life of a product, to include the end of life. BioBuild was founded in 2011 by 14 companies in the European Commission to bring to full scale four carefully selected case studies. The case study this report covers is the External Wall Panel (EWP); it was erected to full scale in May 2015. The EWP is comprised of bio-based materials which is a flax fiber reinforced biopolyester composite. BioBuild is a collaborative project, nonetheless, it has addressed the principles on which a circular economy is founded upon which is to preserve and enhance natural capital, optimize resource yields and foster system effectiveness (Ellen MacArthur Foundation, 2015). Analyzing the various aspects that truly define a circular economy, proposed by the Ellen MacArthur Foundation and Accenture, BioBuild demonstrates that a circulars economy exists.