Development and characterisation of nano-multilayer CrAlSiN coating systems for cutting tools

Ji, Ran (2013). Development and characterisation of nano-multilayer CrAlSiN coating systems for cutting tools. University of Birmingham. Ph.D.

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Abstract

Two types of CrAlSiN nano-multilayer coating were designed and synthesised on AISI M2 high speed steel. Selected coatings were also deposited on pre-nitrided M2 substrate to investigate the effect of duplex treatment. A series of type I CrAlSiN coatings, which have sharp interfaces between individual nano-layers, were designed with varying bilayer thickness. An fcc and an hcp phase were identified for all type I coatings, and it has been found that the bilayer thickness has a significant influence on the orientation of both phases, which in turn affects their mechanical properties. Type II CrAlSiN coatings, with blurred interfaces, were synthesised with a medium bilayer thickness. Due to the insignificant difference in composition between neighbouring nano-layers, only one fcc phase was found in type II CrAlSiN coating. The wear resistance of the new nano-multilayer CrAlSiN coating is about 10 times higher than CrN when tested at room and elevated temperatures. This could be attributed to high H/E ratio and good oxidation resistance conferred by the nano-multilayer structure and multi-component composition. It is also found that duplex treatment can improve the wear resistance of nano-multilayer coating by two orders of magnitude due to the improved load bearing capacity of the coating system.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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