Thesis-1994-Naeem.pdf (9.83 MB)
Chemically vapour deposited α-alumina coatings on high speed steel cutting tools
thesis
posted on 2014-02-11, 14:50 authored by Zakia NaeemA detailed study has been made of the atmospheric pressure chemical vapour deposition
(CVD) of aluminium oxide (Al2O3) coatings on powder metallurgy (PM) BT42 grade high
speed steel (HSS) indexable cutting tool inserts. To facilitate this, a laboratory-scale CVD
reactor was initially designed and purpose-built.
The literature on the effect of process parameters on Al203 coatings chemically vapour
deposited on cemented carbide substrates was comprehensively surveyed. With reference to
deposition conditions quoted in this literature, a series of trial Al203 coating runs were then
performed using uncoated and TiN, TiC and Ti(C1N) precoated PM HSS inserts. Concurrently,
modifications to the laboratory-scale CVD reactor were made. Eventually, deposition
conditions were established under which a preliminary a Al203 coating could be deposited
on the PM HSS inserts and, in the case of the Ti(C1N) precoated inserts only, substantially
retained during the obligatory post-coating HSS substrate heat treatment. The effect of the
absence/presence and type of precoating on the CVD of AI203 coatings on the PM HSS inserts
are discussed. Subsequent coating runs were carried out only on Ti(C1N) precoated inserts.
The characteristics of the preliminary AlP, coating on the Ti(C1N) precoated PM HSS inserts
were determined, both before and after the obligatory HSS substrate heat treatment, using an
established characterisation procedure. This involved the following techniques: X-ray
diffraction, Auger electron spectroscopy, optical microscopy, fractography, scanning electron
microscopy, microhardness testing, profilometry and scratch-adhesion testing. Although
many of the characteristics of the preliminary AI20, coating were found to be inferior to those
presented in the literature, they were also established to be essentially unaffected by the
post-coating HSS substrate heat treatment.
To im prove upon the preliminary Al203 coating, the effect of two of the most important CVD
process parameters quoted in the literature; C02JH 2 mole ratio and Alel3 concentration, on
the characteristics of Al20, coatings chemically vapour deposited on the Ti(C1N) precoated
PM HSS inserts was investigated. Both parameters were found to have a significant effect
on Al203 coating characteristics. The reasons for this are discussed in detail.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© Zakia NaeemPublication date
1994Notes
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.594421Language
- en