Microstructural, Mechanical and Tribological Characterisation of CVD and PVD Coatings for Metal Cutting Applications

The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment.  In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions. The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties.  Through the deposition of well designed bonding and template layer structures the above problems may be eliminated. Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts. Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting. In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.

Parenthood in transition : Somali-born parents' experiences of and needs for parenting support programmes

BACKGROUND: Pre- and post-migration trauma due to forced migration may impact negatively on parents' ability to care for their children. Little qualitative work has examined Somali-born refugees' experiences. The aim of this study is to explore Somali-born refugees' experiences and challenges of being parents in Sweden, and the support they need in their parenting. METHODS: A qualitative descriptive study was undertaken. Data were collected from four focus group discussions (FGDs) among 23 Somali-born mothers and fathers living in a county in central Sweden. Qualitative content analysis has been applied. RESULTS: A main category, Parenthood in Transition, emerged as a description of a process of parenthood in transition. Two generic categories were identified: Challenges, and Improved parenting. Challenges emerged from leaving the home country and being new and feeling alienated in the new country. In Improved parenting, an awareness of opportunities in the new country and ways to improve their parenting was described, which includes how to improve their communication and relationship with their children. The parents described a need for information on how to culturally adapt their parenting and obtain support from the authorities. CONCLUSIONS: Parents experienced a process of parenthood in transition. They were looking to the future and for ways to improve their parenting. Schools and social services can overcome barriers that prevent lack of knowledge about the new country's systems related to parenthood. Leaving the home country often means separation from the family and losing the social network. We suggest that staff in schools and social services offer parent training classes for these parents throughout their children's childhood, with benefits for the child and family.