Effects of gas flow on detailed microstructure inhomogeneities in LPCVD TiAlN nanolamella coatings
Artikel i vetenskaplig tidskrift, 2020

Depositing homogeneous TiAlN coatings with a high Al content on cutting tool inserts is a challenging task. In this work, high-Al cubic Ti1-xAlxN coatings (average x = 0.8) with periodic Ti(Al)N (x = 0.5) and Al(Ti)N (x = 0.9) nanolamellae structure were synthesized by low pressure chemical vapour deposition (LPCVD) with different gas flow velocities, and the detailed microstructure was investigated by electron microscopy and simulations. Using a high gas flow rate, the columnar TiAlN grains with regular periodic nanolamella structures disappeared, the coating became enriched in Ti and hexagonal AlN (h-AlN) formed in the coating. The high Ti content is suggested to be caused by the high gas flow rate that increases the mass transport of the reactants. However, this does not influence the Al-deposition much as it is mainly limited by the surface kinetics due to the relatively low deposition temperature. Density functional theory (DFT) modelling and electron microscopy showed that h-AlN tends to form on the Ti(Al)N phase with a specific crystallographic orientation relationship. The Ti enrichment due to high gas flow rate promotes the formation of h-AlN, which therefore deteriorates the nanolamella structure and causes the disappearance of the columnar TiAlN grains. Thus, by designing the CVD process conditions to avoid too high gas flow rates, homogenous TiAlN coatings with high Al content and nanolamella structures can be deposited, which should yield superior cutting performance.

DFT

TiAlN

CVD

Transmission electron microscopy

EBSD

Författare

Ren Qiu

Chalmers, Fysik, Mikrostrukturfysik

Axel Forslund

Kungliga Tekniska Högskolan (KTH)

Olof Bäcke

Chalmers, Fysik, Mikrostrukturfysik

Anand Harihara Subramonia Iyer

Chalmers, Fysik, Mikrostrukturfysik

Mohammad Sattari

Chalmers, Fysik, Mikrostrukturfysik

Wiebke Janssen

Walter AG

Thorsten Manns

Walter AG

Johannes Kümmel

Walter AG

A. Ruban

Kungliga Tekniska Högskolan (KTH)

Dirk Stiens

Walter AG

Hans-Olof Andrén

Chalmers, Fysik, Mikrostrukturfysik

Mats Halvarsson

Chalmers, Fysik, Mikrostrukturfysik

Materialia

25891529 (eISSN)

Vol. 9 100546

CVD 2.0 - En ny generation av hårda beläggningar

Stiftelsen för Strategisk forskning (SSF), 2016-05-01 -- 2021-06-30.

Ämneskategorier

Oorganisk kemi

Bearbetnings-, yt- och fogningsteknik

Annan materialteknik

Infrastruktur

Chalmers materialanalyslaboratorium

DOI

10.1016/j.mtla.2019.100546

Mer information

Senast uppdaterat

2020-08-28