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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Residual stress in CVD coatings : Evaluation of XRD and TEM methods for micro and macrostress determination

Karlsson, Dennis January 2015 (has links)
Cutting tools are subject to extreme environment during processing, with hightemperatures and pressures. CVD coatings are used to increase lifetime andperformance of the WC/Co composite. Residual stresses in the coatings areinteresting as they may be destructive or constructive for the material duringoperation. Blasting is used to change the as-deposited tensile stress to compressive.The usefulness of X-ray diffraction (XRD) and nanobeam diffraction (NBD) forcharacterization of strains in the different coating layers has been investigated. XRDwith different anode materials has been used to determine the macrostress in thelayers and an attempt was done to calculate the average microstrain and crystallitesize. NBD was used to study the microstrain within single grains of the differentmaterials. A specimen preparation method has been developed for the studiedsamples using the FIB.The XRD analysis shows that the measurement condition is of great importanceduring stress measurements. The macrostress of the different samples show that theZrCN type coating is less stressed than the TiCN type coating after deposition. It isalso shown that the ZrCN type coating is less affected by the blasting. Determinationof microstrain and crystallite size from XRD needs further development.The NBD is a good method to evaluate microstrain within single grains, or betweengrains oriented in the same zone axis. The analyses show more strain within thegrains after blasting. The measurements indicate more strain variation in the Al2O3layer in the TiCN system compared to the ZrCN system.

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