Hot stamping of aluminium alloys allows for increased formability, decreased springback and the possibility of integrating age-hardening heat treatments into the process. However, it can be challenging due to the occurrence of material transfer of aluminium onto the tool, as aluminium is prone to adhesion even at low temperatures. Hence, lubrication is always necessary when forming aluminium, but lubricants can still fail, leading to direct interaction between tool and workpiece and thus material transfer. This phenomenon reduces the efficiency of the process, as interruptions are necessary for the refurbishment of the tools. Understanding of how material transfer takes place is important in order to find new or improved solutions, in terms of lubrication and surface engineering, to prevent adhesion. Nevertheless, current research in high temperature tribology of aluminium, mainly in terms of material transfer mechanisms, is very limited, as many of the works focus on lubricated conditions and do not look into the fundamental interactions between aluminium alloys and tool steels. In this context, the aim of this work is to investigate the mechanisms behind the occurrence of aluminium alloy transfer onto tool steel during sliding at high temperature and in dry conditions. A hot-strip drawing tribometer was used to perform tests at room temperature, 300°C, 400°C, and 500°C, directly after solubilizing the aluminium alloy at 520°C. Two different topographies for the tool steel were used: ground and polished. Material transfer characterization was performed mainly through scanning electron microscopy. It was found that grinding marks (ground tool steel) and carbides (polished tool steel) act as initiation sites for the transfer to occur. Temperature plays a role on the growth mechanisms of the transfer films during sliding, as thermal softening of the aluminium alloy is the dominant factor in determining the growth direction of the transfer layers. A growth towards the trailing edge (shearing and smearing of the transferred aluminium) or a growth towards the leading edge (build-up of transferred aluminium, leading to a thicker and more localized transfer material).

Machining of Aluminum can be complicated due to large amounts of adhesion and diffusion of the aluminum onto the cutting tool, causing effects such as built-up layers and built-up edges. This leads to poor surface finishes and can significantly affect the tool life. CVD diamond coated tools have shown to be a potential solution to this problem and is tested and analyzed as such in this thesis. CVD diamond coated inserts are tested and compared to uncoated cemented carbide inserts and Polycrystalline diamond tipped inserts, in milling, turning and in refined tribological methods. The workpiece material in both the machine tests and the tribological tests is a high strength aluminum of the name Alumec 89. The machine tests were performed for 5 and 60 seconds at three cutting speeds, 600, 900 and 1200 m/min, keeping other parameters constant. The cutting inserts, the chips and the generated workpiece surface are examined using LOM, SEM and EDS. In the refined tribological testing, a pin-turning tribometer is used, with pins of uncoated and coated (CVD diamond) cemented carbide pins. These are tested at 5 and 30 seconds at 600 and 1200 m/min, applying a constant force of 10 N. In addition, a friction test was performed to measure the friction of the uncoated and the CVD diamond coated cemented carbide. Like the cutting inserts, the used pins were examined in LOM and SEM. The results show that while a large amount of built-up layer and built-up edges gather when using uncoated cemented carbide tools, only minimal amounts can be detected on CVD diamond and PCD. It has also been shown that the reason for the reduced adhesion in the case of diamond tooling materials is most likely due to the lack of chemical interactions between the diamond and the aluminum. The friction of the CVD diamond material was shown to be lower compared to the cemented carbide. The surface finish generated by the different materials, was the best in the case of PCD while the CVD generated multiple small scratches that severely reduced the surface roughness. This thesis provides some initial basic understanding of the interaction of CVD diamond coated inserts with high strength aluminum alloys.

Fräsning och annan intermittent skärande bearbetning ger upphov till termisk utmattning av skärverktyg. Problemet med termiska sprickor blir större vid bearbetning av värmehållfasta material som austenitiskt rostfritt stål eftersom värmeväxlingarna i skärverktyget blir mer extrema. Detta fenomen förvärras ytterligare vid användning av traditionell kylning. Fräsning av rostfritt stål utförs därför torrt. Den torra bearbetningen är inte oproblematisk eftersom höga temperaturer uppstår i skärzonen vilket påverkar verktygets livslängd och i vilken utsträckning avverkningshastigheten kan höjas med högre skärhastighet eller matning. Detaljer som tar lång tid att tillverka är negativt för både företagens ekonomi och miljön till följd av större energiåtgång.Minimalsmörjning är en metod som går ut på att små mängder smörjmedel i form av aerosol fokuseras mot skäreggen och smörjer kontakten mellan arbetsstycke och skär, vilket minimerar friktionsvärmen. På detta sätt kan den totala värmeutvecklingen reduceras samtidigt som värmeväxlingarna hålls på en lägre nivå jämfört med traditionell kylning. Syftet med arbetet var att undersöka och jämföra planfräsning av austenitiskt rostfritt stål, 1.4301, under torr bearbetning och bearbetning med minimalsmörjning.Centralt för studien var hur verktygsförslitningen och ytjämnheten hos bearbetat material påverkas då minimalsmörjning appliceras gentemot vid torr bearbetning.En fråga som togs upp var om avverkningshastigheten kunde ökas med minimalsmörjning utan att få negativ inverkan på verktygsförslitning och ytjämnhet av bearbetat arbetsstycke.Fullfaktorförsök upprättades och jämförelsen mellan torr bearbetning ochminimalsmörjning gjordes med planfräsning med PVD-belagda hårdmetallskär. Ett optiskt mätmikroskop användes för att analysera förslitningen på skärverktygens spån- och släppningssidor efter ca 3 minuter i ingrepp. Ytjämnhet på bearbetad ytamättes med ytjämnhetsmätare och temperaturen i arbetsstycket mättes med termoelement.Resultatet visade att tillämpning av minimalsmörjning sänker temperaturen i skärzonen vilket för rostfritt stål innebär att skärhastigheten bör ökas för att undvika löseggsområdet. På så sätt ökar även avverkningshastigheten och produktiviteten. / Milling and other intermittent metal cutting operations often cause thermal fatigue in the cutting tools used. This type of wear is more severe during machining of heat resistant alloys such as austenitic stainless steel because of more extreme temperature variations during the cutting procedure. This phenomenon is further accelerated by employing flood cooling. Milling of stainless steel is therefore usually performed dry. Dry cutting is, however, not without its share of problems, since high temperatures develop in the cutting zone which adversely affect tool life and to which extent the productivity can be increased via higher cutting speeds or feed rates. Parts that take longer to manufacture are not only bad for business economics, but also for the environment due to higher energy consumption.Minimum quantity lubrication is a method that uses minimal quantities of oil dispersed as aerosol toward the cutting edge. This lubricates the tool-workpiece interface which minimizes frictional heat. This way, the total heat during cutting can be reduced while also avoiding the extreme temperature variations associated with flood cooling. The purpose of this thesis is to study and compare the performance of dry cutting and minimum quantity lubrication during face milling of austenitic stainless steel, 1.4301.The tool wear rates of the cutting tools and surface quality of the machined workpiece were compared for the two cutting environments. Of particular interest was the question whether the material removal rate could be increased with the usage of minimum quantity lubrication without adversely impacting the tool life or workpiece surface quality.A full factorial design of experiments was created, and the comparison of dry machining and minimum quantity lubrication was done by face milling with PVDcoated carbide inserts. An optical stereo microscope was used for the analysis of rake and flank wear after roughly 3 minutes of cutting tool engagement. Surface roughness of machined part was measured with a measuring stylus, and the temperature of the workpiece was measured with embedded thermocouples.The results show that minimum quantity lubrication reduces the temperature in the cutting zone, which for stainless steel means that the cutting speed should be increased to avoid the formation of built-up edges. At the same time, the material removal rate is increased, and productivity is affected positively.

Internal Combustion Engine (ICE) exhaust components are exposed to extreme operating temperatures. Thus, it is necessary that they are designed with materials that can sustain thermal and vibrational stresses. This study investigates the wear mechanisms and tribological performance of the exhaust manifold joint in Scania CV diesel trucks, focusing on the lip seal ring between the exhaust and turbo manifolds. The joint is prone to wear due to thermal and vibrational stresses, impacting its service life and raising environmental concerns. The manifold material, ductile cast iron SiMo51, offers good thermal resistance, while the lip seal ring, made of Inconel 718c, provides excellent thermal fatigue and corrosion resistance, coated with AlTiN for wear and oxidation resistance. However, the tribological performance of this joint and material combination remains unknown, necessitating further research.  This work aims to understand wear initiation mechanisms and their relationship with temperature. Test setups were established using an oscillating cylinder on disc configuration in the SRV 3 tribometer. SiMo51 uncoated/coated with Tribaloy 400 and Inconel 718c uncoated/coated with AlTiN were tested against each other to identify the best material pair. Analysis involved coefficient of friction, visual inspection, wear volume measurements, SEM micrographs, and EDS for surface chemical composition. Results indicated that friction behaviour is temperature-dependent, with oxide layer formation reducing the coefficient of friction when the manifold is uncoated, while the opposite occurs when coated with Tribaloy 400. Wear behaviour varied based on material combinations and temperature. Uncoated manifold exhibited dominant adhesion (galling) accompanied by tribo-oxidation at higher temperatures, with maximum wear volumes at room temperature. Introduction of T-400 on the manifold initiated galling on the lip seal, leading to abrasion on the manifold surface, accompanied by tribo-oxidation at elevated temperatures. Wear increased until 500°C, followed by a decrease at 700°C. Further explanations of T-400 wear behaviour are lacking in the literature.

The transition to a Circular Economy scheme that enables a more efficient usage of the resources is one of the most pressing needs in our society. From the industrial perspective this has been translated into new design philosophies and the search for more efficient systems. Polymeric composites have played a key role in the development of lighter components with good mechanical and tribological properties. Specifically, the demand of Carbon Fiber Reinforced Polymers (CFRP) has had an increasing trend since 1970s-1980s, becoming one of the kind of composites with the highest demand in the market to supply industries such as aerospace, automotive, construction, renewable energies, among others. With the increasing demand of CFRP materials some of the main challenges that arise are their disposal, environmental impact and cost of production to maintain the required supply. The use of Carbon Fibers as a reinforcement for polymeric matrices has been widely documented over the last decades, however the characterization of recycled Carbon Fibers for tribological applications is still scarce. Therefore, this investigation is focused on the mechanical and tribological characterization under water lubricated conditions of Ultra High Molecular Weight Polyethylene (UHMWPE) composites reinforced with virgin and recycled Carbon Fibers and Graphene Oxide. The findings of this work provide an important panorama regarding the performance of recycled Carbon Fibers, showing that they can have a comparable performance in mechanical properties and tribological behavior. This enables the use of recycled Carbon Fibers without compromising performance while reducing the environmental impact and cost.

There has been much discussion about the beneficial uses of lamellar graphite iron in piston rings–cylinder liner systems, where a good combinations of both thermal and tribological properties are essential. The excellent tribological performance of lamellar iron under such sliding conditions is principally associated with lubrication behaviour of the graphite particles which are distributed as lamellas throughout the matrix. During sliding, graphite particles are extruded and smeared onto the counterfaces, act as solid lubricating agents and form a thin graphite film between the sliding surfaces. Although this process especially, during the running-in period significantly changes the sliding wear response of the components, the exact mechanism behind of this phenomenon has rarely been discussed in previous studies. It is tribologically beneficial to keep the graphite open, particularly in applications where the scuffing issues do matter. In this thesis, the main causes involved in closing the graphite lamellas are discussed, with a focus on matrix plastic deformation that occurs during sliding. In first step, the relationship between graphite lamellae orientation and plastic deformation was investigated. To do so, two piston rings, belonging to the same two-stroke marine engine operated for different periods of time, were selected and compared to the unworn sample. The worn piston rings displayed a substantial decrease in both frequency and area fraction of the graphite lamellas. Most of the lamellas were closed as a result of plastic deformation of matrix. This happening was caused mainly by the interaction between abrasive particles and metallic matrix. Additionally, it was found that graphite lamellas parallel or near-parallel to the sliding direction exhibited maximum closing tendency under sliding condition. In next step, to have a better understanding of the graphite film formation mechanism and matrix deformation role in closing the graphite lamellas, microindentation and microscratch testing were performed on typical lamellar iron. The qualitative results showed a similar mechanism involving in graphite contribution to lubricate the sliding surfaces. Moreover, microindentations made nearby the graphite lamellas demonstrated that the deformation of the matrix causes the formation of cracks in the centre of the graphite lamellas, compressing and then extruding the graphite from its natural position, irrespective of the lamellas′ size. Furthermore, it was found that subsurface graphite orientation had a large influence on the extrusion behaviour, in that, for graphite lamellas oriented towards the indenter, the effect was observed more pronounced. Furthermore, an improved fully ferritic solution strengthened compacted graphite iron was produced for future wear studies. The effects of different Si levels and section thicknesses on tensile properties and hardness were investigated as well. The influence of Si content and section thickness on mechanical properties was revealed by improving the materials strength and slightly enhancing the hardness through increasing Si content. Besides, Si addition up to 4.5 wt% significantly affected the strength and elongation to failure of cast samples. / Helios / FFI

Achieving sustainable lubrication by using environmentally friendly formulated lubricants has became an essential component of the transition process from fossil-powered vehicles to electrified transportation. Mixtures, or aqueous solutions of molecules such as polyhydroxy alcohols, and glycols usually known as green lubricants make it possible to achieve low friction coefficients under different lubrication conditions, which constitutes a potential alternative to improve the tribological performance of moving parts in automotive systems, at the same time that the environmental requirements are satisfied. There is a need to improve the protection against mild-wear and micropitting offered by green-lubricants before consider using them in the transmission gear box of battery electric vehicles BEVs, where their low shear-stress resistance can potentially help to improve the vehicle efficiency. Therefore, this research work aims to gain understanding of the tribological behaviour of rolling-sliding elements under glycerol-based lubrication, with focus on assessing the influence of different glycerol-based lubricant formulations on the wear modes associated to rolling contact fatigue such as micropitting, and macropitting.  Micropitting tests were carried out by using a micropitting rig, with a roller on ring planetary configuration. The evolution of microcracks, and micropitting was studied for several glycerol-based lubricants at different slide-to-roll ratios (SRRs) 5-30%, and different load contact conditions 1.5-2.5 GPa. A comparison against a fully formulated transmission oil has been performed. A relationship between the surface damage morphology and the operating conditions has been established. The lubrication regimes of DLC coated contacts and uncoated contacts in presence of glycerol-based lubricants were investigated through the construction of 3D friction maps, and Stribeck curves in a wide range of rolling speeds, and SRR testing conditions. The capability of two different DLC coating systems to prevent micropitting onset due to rolling contact fatigue in presence of glycerol-based lubricants was studied: Cr/a-WC:H/a-C:H and a-C:Cr.  Under mixed-lubrication regime it was found that a reduction up to 51% of friction can be achieved by using glycerol-based lubricants compared to a commercial transmission oil. The initial low friction coefficients at low contact cycles was attributed to the low pressure-viscosity coefficient of the glycerol-based lubricants. Friction was even further reduced with the increasing contact cycles since glycerol aqueous solutions were found to promote mild-wear, causing a smoothing of the surface asperities and therefore an enhancement of the hydrodynamic effect due a higher lambda ratio (Λ), making possible to trigger superlubricity in the contact. Surface micro-cracking was found to decrease at low SRR values under glycerol-based lubrication contrasted to the contacts lubricated with a fully formulated transmission oil. Once microcracks were nucleated, micropitting progressed faster in the contacts lubricated with glycerol-based lubricants, while micropitting was null or significantly delayed in presence of transmission oil. With the increasing SRR surface microcracks density and micropitting was found to became higher. The reduction of microcracks density with a glycerol-glycol based lubricant was attributed to the adsorption of long glycol molecules on the steel surface that avoid the direct interaction between asperities. The faster micropitting progression was attributed to the presence of dissolved water in the contact. Thin DLC a-C:Cr coatings were shown to significantly mitigate the penetration of surface initiated pits into the steel substrate, which was translated in a lower volume loss. Local micro-delamination was found to be the main reason behind coating failure in presence of glycerol-based lubricants, as a result, pitting took place on the steel exposed areas.

Grease is among the most widely used lubricants in rolling element bearings. Proper understanding of the effect of lubrication due to grease aging can provide a significant increase in the life of the engineering systems. However, at present, there is no sufficient understanding of the grease aging effect in rolling elements bearing. This restricts the optimal usage of the bearing and timely monitoring of the grease. The current research work tries to address this issue with an experimental investigation. This project studies the behavior of 4 types of greases in rolling elements bearings for various operating conditions by recording the temperature and acoustic emission data. The aged samples were prepared to keep in the oven at 150 °C for a series of time duration letting it go through the chemical changes and thermal degradation. Tests were carried out in a test rig with the different levels of oxidized greases for 5 hrs time. And the effects in bearing temperature, acoustic emission were recorded. This is an investigation to analyze the effects of grease composition and aging in rolling elements lubrication by means of acoustic emission and bearing temperature. The IR spectroscopy was carried from the samples collected from the oven in order to understand the change in lubricant composition. The results show that the grease with di-urea thickener and base oil of synthetic ether and polyolester gives the best bearing temperature and acoustic emission behavior compared to the other grease type. The possibility of using the acoustic emission and temperature data to monitor the grease aging is also presented. Along with this, the possibility of using the AE statistical methods, AE count method, and energy plot were also explored to relate with the degree of aging.

The global shift towards sustainable practices extends across various domains, including energy generation. Wind energy, a cornerstone of this transition, relies heavily on the efficient operation of wind turbines. This study investigates the impact of contaminants on the longevity and performance of blade bearings in wind turbines. Under real-world conditions, blade bearings frequently operate in suboptimal lubrication environments, attacked by contaminants like wear particles and water. This research, conducted in collaboration with Vattenfall R&D, aims to focus on the specific effects of these contaminants.  Through comprehensive literature reviews and tribological tests, the study evaluates the load in rolling elements, examines the contact conditions between raceways and rollers, and determines the effects of contaminants on wear volume. Findings indicate that most pitch movements in blade bearings are limited to small angles, influencing lubrication requirements and wear patterns. Chloride-based EP additives, probably inactive due to insufficient activation temperatures, show potential for hydrolysis-induced corrosion.  Wear tests suggest that used grease may perform better under certain conditions compared to fresh grease, highlighting the complexity of lubricant performance. Long-term tribological tests show that FUCHS LUBRITECH GLEITMO 585K exhibits better wear resistance compared to Shell Rhodina BBZ in test conditions.  The study underscores the importance of proper lubrication and contamination management in extending blade bearing life. Recommendations include regular grease monitoring and analysis, understanding tribo-corrosion effects, and improving seal compatibility to enhance overall bearing reliability.

Volvo Cars in Skövde manufacture and assemble Volvo engines. When attaching the ignition coil to all 4-cylinder engines, a special mounting tool is required. This mounting tool is currently manufactured from injection-molded polyoxymethylene (POM), a thermoplastic. It has been noted that the life span of the tool is shortened as a result of abrasive wear that occurs during the attachment process of the ignition coil. An investigation of the possibility of manufacturing the mounting tool with a 3D-printer is undertaken in cooperation with ÅF, a consultant to Volvo Cars. A literature study is first presented to introduce broader knowledge on the subject. The abrasive wear and other material characteristics such as tensile strength, compressive strength and elongation of  POM and an alternative material for 3D-printing,  Ultem™, an amorphous thermoplastic polyetherimide are discussed.  These material characteristics are studied further and considered in tandem with both a theoretical analysis and a wear experiment, based on the pin-on-disc method. It is shown in the theoretical analysis that the wear is approximately six times larger for Ultem™ when compared to POM. The wear resistance of Ultem™ is highest when wear occurs parallel to the direction of the printed layers. In contrast, the experiment shows that the wear is about three times larger in Ultem™ than in POM.  The highest tensile strength of Ultem™ is also found in the direction of the printed layers. Some issues with the small elongation of the 3D-printed material are presented. It is recommended that ÅF apply the 3D-printing technique with Ultem™ only for construction details with complex geometries and where the material elongation will not exceed 5%. It is also recommended that ÅF both support and contribute to this innovative technique in order to develop leading edge competence in the subject. / Volvo Cars i Skövde tillverkar och monterar Volvomotorer. Vid monteringen av tändspolen till alla 4-cylindriga motorer behövs ett monteringsverktyg. Detta monteringsverktyg tillverkas för närvarande från formsprutad termoplast polyoximetylen (POM). Det har noterats att livslängden av verktyget förkortas på grund av abrasiv nötning som uppkommer under monteringsprocessen av tändspolen. Möjligheterna att tillverka monteringsverktyget med en 3D-skrivare utvärderas i samverkan med ÅF, en konsult till Volvo Cars. En litteraturstudie presenteras för att introducera en bredare kunskap i ämnet. Den abrasiva nötningen och materialegenskaper såsom draghållfasthet, tryckhållfasthet samt töjning hos POM och ett alternativt material för 3D-skrivning, Ultem™, en amorf termoplast polyeterimid, behandlas. Dessa materialegenskaper studeras vidare och tas i beaktning med både en teoretisk analys och ett nötningsexperiment, baserat på pin-on-disc metoden. Enligt den teoretiska analysen är nötningen hos Ultem™ approximativt 6 gånger större vid jämförelsen med POM. Nötningsbeständigheten hos Ultem™ är högst då nötning sker parallellt med 3D-skrivningsriktningen av lagren. Nötningsexperimenten visar att nötningen hos Ultem™ är ungefär 3 gånger större vid jämförelsen med POM. Den högsta draghållfastheten hos Ultem™ uppkommer också parallellt med 3D-skrivningsriktningen av lagren. Problem med den låga töjningen hos det 3D-skrivna materialet behandlas. ÅF rekommenderas att tillämpa 3D-skrivning med materialet Ultem™ främst för detaljer med komplexa geometrier med en töjning som inte överskrider 5 %. ÅF rekommenderas även att både stödja och bidra till denna innovativa teknik för att kunna skapa en ledande expertis i ämnet.