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<p>The aim of this study was to explore environmentally friendly solutions to reduce the friction present in automotive transmissions.</p> <p>A 2005 Ford Escape Hybrid transmission was used in this study to establish reasonable operating conditions for the gear surfaces.</p> <p>Background on gear operation and surface interaction was studied to understand the nature of the contact between the gear surfaces. Based on this, a mathematical model of gear interaction was developed and used to bracket the loading conditions of the gear tooth interface to be up to 1.5GPa of contact pressure with 2m/s relative sliding velocity. This information was used to aid in the identification of suitable surface engineering technologies and set the operating conditions for reciprocating tribometer based measurements.</p> <p>Additionally, tribological tests were performed on pin-on-disc samples which were treated with various surface treatments. The resulting wear surfaces were then studied using optical and Scanning Electron Microscopy (SEM) as well as Raman Spectroscopy. These techniques were used to better understand the mechanisms associated with wear and the role that the surface treatments played in reducing wear. Based on the testing performed, the best surface treatment for this application was a super finishing process. This process also met cost and environmental constraints. An in-house dynamometer was also developed to be used in the future full scale testing of a transmission.</p> / Master of Applied Science (MASc)

In response to more stringent global CO2 emissions, automotive manufacturers have increased the use of advanced high strength steels (AHSS). Ultra-high strength steels are often used within the body-in-white (BIW) for safety critical parts and structural reinforcements, such as roof rails and side impact beams. Currently, the most commonly used press hardened steel (PHS) grade for these applications is 22MnB5, with a typical composition of 0.22C 1.2Mn 0.25Si 0.005B (wt%). Automotive OEMs have expressed a desire to use Zn-based coatings as they are compatible with the current painting system and have the potential to provide robust cathodic protection. The steel blanks generally undergo direct hot press forming (DHPF) to achieve the necessary martensitic microstructure and target mechanical properties, but this presents challenges for Zn-coated 22MnB5. The adoption of Zn-based coatings within the automotive industry has been inhibited by the prospect of liquid metal embrittlement (LME) resulting from DHPF, as well as the desire to provide robust cathodic protection. Previous literature has reported that a zinc ferrite (α-Fe(Zn)) coating with a global Zn content of at least 30 wt% will provide cathodic protection to the underlying substrate. The main goal of this work was to determine the microstructural evolution and electrochemical properties of galvanized (GI70 – 70 g/m2/side) 22MnB5 substrates as a function of the annealing time at a typical austenization temperature of 900°C. It was found that the Zn-based coatings annealed at 700°C consisted to a mixture of small volume fraction of α-Fe(Zn) and Г-Fe3Zn10. After heating to 900°C, the coating comprised varying volume fractions of α-Fe(Zn) and Zn(Fe) liquid, which transformed to Г-Fe3Zn10 after solidification. The relative fraction of Г Fe3Zn10 was found to decrease with increasing annealing time until the coating completely transformed to α-Fe(Zn) after annealing at 900°C for 240 s. GDOES results found that, when the sample was annealed at 900°C for 240 s, the global Zn content of the coating was less than 30 wt%. Coatings comprising varying fractions of Г-Fe3Zn10 were subjected to uniaxial tensile tests to determine how the coating microstructure affected the mechanical properties in comparison to the uncoated substrate material. It was found that the uncoated substrate material met the mechanical property requirements of σ(UTS)min ≥ 1500 MPa regardless of annealing time. However, σ(UTS) was found to decrease with increasing annealing times for the GI70 coated samples until the target mechanical properties were not met when the sample was annealed at 900°C for 180 s. This was attributed to increased coating thicknesses leading to a decrease in the martensitic cross-sectional area to support the load. Furthermore, the coatings were subjected to a variety of electrochemical characterization techniques, including potentiodynamic and galvanostatic polarization scans, potentiostatic scans, and electrochemical noise tests. Potentiodynamic polarization scans indicated a higher driving force for cathodic protection when the coating contained some fraction of Г-Fe3Zn10. Furthermore, a limiting current density for these samples was observed, demonstrating that Г-Fe3Zn10 corrodes at a slower rate in comparison to α Fe(Zn). Galvanostatic polarization measurements indicated that, when the fraction of Г Fe3Zn10 within the coating was below 15 vol%, the protective properties of the phase were not exhibited. XRD and TEM analysis revealed the formation of three corrosion products on the surface: simonkolleite, hydrozincite, and akaganeite. It was found that, when samples contained greater than 15 vol% Г-Fe3Zn10 in the coating, the predominant corrosion products were a combination of simonkolleite and hydrozincite. When the Г Fe3Zn10 content was below this value, the dominant corrosion product was found to be akaganeite. Furthermore, substrate attack was observed on a sample annealed at 900°C for 420 s when the coating layer was intact, indicating that the α-Fe(Zn) only containing coating obtained at this time does not provide cathodic protection. Based upon the current results, it was determined that a minimum volume fraction of 15 vol% Г-Fe3Zn10 must be present within the coating layer to obtain robust cathodic protection. Furthermore, it was determined that the processing window to develop cathodically protective Zn based coatings while mitigating LME is extremely narrow. This is a result of the fact that it is necessary for at least 15 vol% Г-Fe3Zn10 to be present within the coating microstructure at room temperature, which is liquid at the forming temperatures of 900°C. From the current findings, it was found that it is unlikely that a cathodically protective Zn-based coating can be obtained for DHPF steel parts using 22MnB5 as a substrate material. This is due to the high forming temperature resulting in liquefication of the coating and the rapid cooling rates necessary to achieve the target mechanical properties of σ(UTS)min ≥ 1500 MPa. Thus, it is recommended that the current substrate material be altered such that the part may be formed below the peritectic temperature of 782°C. / Thesis / Master of Applied Science (MASc)

This thesis aims at investigating the feasibility of realizing antireflection (AR) and high-reflection (HR) to the semiconductor waveguide end facet using monolithically integratable deep-etching technology to replace the conventional thin film dielectric coating counterpart. Conventional AR coating and HR coatings are the building blocks of semiconductor optical amplifier and semiconductor lasers. In this thesis, the AR coating and HR coating are first studied systematically and comprehensively using two computational electromagnetics approaches: plane wave transmission matrix method (TMM) and finite difference time domain (FDTD) method. The comparison of the results from the two approaches are made and discussed. A few concepts are clarified based on the different treatment between the AR coatings for bulk optics and those for semiconductor waveguide laser structure. The second part uses the same two numerical tools and more importantly, the knowledge gained from the first part to analyze and design deep-etched waveguide gratings for the advantage of ease of monolithic integration. A variational correction to the TMM is provided in order to consider effect of the finite etching depth also in the plane wave model. Specially, a new idea of achieving AR using deep-etched waveguide gratings is proposed and analyzed comprehensively. A preliminary design is obtained by TMM optimization and FDTD verifications, which provides a minimum power reflectivity in the order of 10-5 and a bandwidth of 45nm for the power reflectivity less than 10-3. In order to eliminate the nonphysical reflections from the boundary, the perfectly matched layer (PML) absorbing condition is employed and pre-tested for antireflection analysis. The effects of etching depth and number of etching grooves are specifically analyzed for the performance of proposed structures. Numerical results obtained by FDTD method indicate a promising potential for this alternative technologies. / Thesis / Master of Engineering (ME)

Super Duplex Stainless Steels (SDSS) are widely used in offshore oil and gas industrial components. They are dual phase materials consisting of ferrite and austenite in similar ratios with high contents of chromium and presence of molybdenum. This combination of microstructure and chemical composition results in enhanced mechanical strength and corrosion resistance. However, this material has poor machinability, exhibiting the following characteristics: (i) tendency to strain-harden; (ii) extreme adhesive behaviour; and (iii) high cutting temperatures. These circumstances not only result in high tool wear rates, but also lead to poor surface integrity due to the work hardening effect, high roughness and tensile residual stress. To minimize these detrimental effects, PVD coating technologies have been widely applied to cutting tools due to their tribological properties exhibited during cutting, which reduce friction and diminish heat. In this work, three different PVD coatings were tested during the turning of super duplex stainless steel of grade UNS S32750. In addition to the tool performance, surface integrity was assessed by surface texture analysis, residual stresses and hardness profile. The electrochemical behaviour of the machined surface was evaluated by potentiodynamic anodic polarization measurements. Stress cracking corrosion (SCC) tests were also performed. Results indicate a relationship between the tool performance and surface electrochemical behaviour, where the tool with best cutting performance, AlTiN, also presented the best electrochemical behaviour. Stress cracking corrosion was found to be associated with residual stresses on the workpiece, among the three tested PVD coated tools the AlCrN/TiSiN showed lowest tensile residual stresses and lowest SCC susceptibility. The surface generated by AlTiN coated tool presented the highest levels of tensile residual stresses, resulting in a higher SCC susceptibility. / Thesis / Master of Applied Science (MASc)

No / This study investigates the effect of heat treatment on changes in microstructure and wear behaviour of WC-NiCr coatings. Two feedstock powders with a similar chemical composition and different particle sizes (near nano-structured WC-17NiCr and microstructured WC-15NiCr) were used. High-velocity oxyfuel spraying technique was used to deposit coatings on to a mild steel substrate using identical spraying parameters. Coated samples were then heat treated in a nitrogen atmosphere at 500 and 700°C. The effect of heat treatment on changes in hardness and wear performance of the coatings was studied using microstructural analysis, micro-hardness indentation and abrasive wear tests. The results showed that the heat treatment increased the hardness of both coatings and a corresponding increase in wear resistance was recorded. The formation of a brittle CrWO4 phase in the microstructured coating resulted in brittle fracture of the coating and this gave lower wear resistance compared to the nanostructured coatings.

Three hydrocolloid-lipid emulsion coatings were developed using Humkote brand partially hydrogenated cottonseed and vegetable oil, and one of three combined hydrocolloid bases: xanthan gum and propylene glycol alginate (xanthan coating), locust bean gum and xanthan gum (locust bean gum coating), and maltodextrin. Sensory testing using a ranking preference test indicated that these coatings had acceptable appearance and palatability. Quality characteristics of green bell peppers (Capsicum annum L. cv. King Arthur) measured during the 5-week storage period included: respiration rates, chlorophyll content, surface color, puncture force, pectin (uronic acid) content, ascorbic acid (AA) and dehydroascorbic acid (DHA) content, and cumulative weight loss. No significant differences between coated and uncoated peppers were noted in tests for respiration, puncture force, hue angle, chlorophyll content, and AA content. Uncoated peppers had significantly inferior moisture retention (p<0.05), which caused them to be unsaleable after 8 days, while coated groups were saleable for an additional 6 to 8 days. Uncoated fruits also had greater uronic acid breakdown (p<0.05) and higher DHA content (p<0.06) than coated peppers. Significant weekly changes (all treatment groups combined) included linear increases in respiration rates (p<0.01) and moisture loss (p<0.01), increasing linear and quadratic trends in uronic acid content (p<0.01 for both trends), increasing quadratic trends for both chlorophyll and AA content (p<0.05, p<0.01, respectively), and decreasing linear and quadratic (p<0.05 for both trends) in DHA content. The only significant difference between coated groups was in chroma value, with maltodextrin coated peppers appearing less vivid than locust bean coated peppers. Overall, all three coatings performed equally well during the storage study. However, coatings with higher lipid content, which included xanthan gum and locust bean gum groups, withstood humidity changes better than the maltodextrin coated peppers. Coating application provided the greatest benefits in terms of texture maintenance through water retention and prevention of pectin breakdown, despite the lack of differences observed in puncture force. Coatings may also have prevented AA oxidation as demonstrated by the higher DHA content in uncoated groups, however AA patterns do not confirm this concept. Future research should be directed toward further minimizing textural changes and maximizing coating durability. / Ph. D.

Fretting of solvent cast polyimide coatings was investigated in a ball-on-flat geometry as a function of relative humidity. Polyimides were synthesized from benzophenone tetracarboxylic dianhydride (BTDA) and bisanline (Bis P), 6-fluoro bis dian hydride (6FDA) and Bis P, and pyromellitic dianhydride (PMDA) and bis A phenyl phosphine oxide (BAPPO). Coating life - the time for the steel ball to wear through the coating - shortened with increasing humidity. Iron oxides or other reaction products from 52100 ball generated at high humidity acted as abrasives and accelerated the wear of the coatings. Variation of coating life among the three polyimides was attributed to the residual stress, which developed upon cooling from the annealing temperature due to the mismatch of thermal expansion coefficients between the polymer and the metal substrate. Calculated from elasticity theory, the normal stress dropped shortly after the start of the test, remained relatively constant, and increased toward the end. This variation correlated with the wear rate and accounted for the non-linear increase of coating life with coating thickness. Sub-surface shear stress and surface tensile stress predicted well, respectively, the debonded shape and the inter-crack spacing of Hertzian cracks. / Ph. D.

The purpose of this study is to characterize the plasma spray deposits used for attaching intrinsic Fabry-Perot interferometric fiber optic strain sensors. The deposits must maintain adhesion at elevated temperatures without distorting the sensors' signals. Two different material systems were tested and modeled, a nickel based alloy and yttria-stabilized zirconia. The material properties of the deposits and the thermal stresses in the system were evaluated to determine attachment lifetime of the sensors. The encapsulated sensors' signals were collected before and after plasma spraying and at elevated temperatures. The material properties of the deposits were evaluated by electron microscopy, energy dispersive x-ray spectroscopy, scratch testing, thermal fatigue testing, and nanoindentation. The thermal stresses were evaluated by Raman spectroscopy and from finite element analysis in COMSOL® Multiphysics®. Several of the sensors broke during encapsulation due to the plasma spray processing conditions and the signals experienced distortion at elevated temperatures. The sensors can be treated to remove this interference to allow for this deposit attachment. The nickel based alloy's ductility and lamellar microstructure allowed for non catastrophic relaxation mechanisms to relieve induced thermal stresses. The yttria stabilized zirconia failed catastrophically at elevated temperatures due its lack of compliance to mismatches in thermal expansion. A high melting point metallic deposit, similar to the nickel based alloy, is desirable for fiber optic sensor attachment due to its ductility, thermal expansion, and dominant relaxation mechanisms. The processing conditions may need to be optimized to allow for the sensors' protection during encapsulation. / Master of Science

Glass, sapphire and polymer fibers transparent to visible and infrared electromagnetic frequencies are extensively used in communication and sensing. The lifetimes of these waveguides are extended considerably by suitably coating them. Plastic coated silica waveguides are gradually replacing metal coaxial cables used in communications and they have been used successfully in various types of sensing. Unfortunately plastic coatings cannot withstand very high temperatures. In order to perform contact or invasive sensing in the medium to high temperature range and in harsh environments, other appropriate coating materials have to be used. This thesis examines various refractory materials as candidate coating materials. Coating materials should not react chemically with the waveguide material but should have matching thermal expansion coefficients. Refractory materials are examined in detail for thermodynamic suitability for both sapphire and silica waveguide cores and claddings. The candidate coating materials selected are alumina, silicon carbide, zirconia and metal niobium. Experimental verification of the chemical inertness of these materials with silica and sapphire in very low pressure and at 857°C temperature is studied. The materials found suitable for coating can be coated using the various methods discussed. Fibers suitably coated with these materials would be suitable for high temperature sensing in harsh environments and in situ within advanced high temperature composites. Metal niobium does not react with sodium and is thermodynamically compatible with alumina which is also a very stable refractory material. Multilayer coatings of niobium and alumina on sapphire exposed to harsh environmental conditions can prolong the life of the sapphire waveguide. X-ray diffraction and electron microprobe analyses of the single oxides and carbides, namely, alumina, silicon carbide and zirconia and the metal niobium, were conducted. It was found that sapphire did not react with any of the selected ceramics; the silica fiber underwent structural change in the silicon carbide matrix and the change was macroscopic. Within the restricted environment, the silica fiber appeared not to react with the alumina, zirconia and niobium matrices. This thesis specifically considers the possibility of using the various ceramics as coating materials without analyzing the nature of the phases present. Hence detailed analyses of phases were not made when macroscopic change in fiber structure was observed or as observed during the x-ray analyses and microprobe analyses. / Master of Science