Thermal stability of Al–Cr–N hard coatings

Willmann, Herbert; Mayrhofer, P.H.; Persson, Per; Reiter, Andreas; Hultman, Lars; Mitterer, Christian

doi:10.1016/j.scriptamat.2006.02.023

Cited by 246 publications

(105 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Besides the XRD peaks arisen from the Si substrate (marked as Si in the figure), other two evident peaks at around 2q ¼ 37.5 and 43.6 could be attributed to the rocksalt-type cubic phase CrN (111) and (200), respectively, similar to Ref. [26,27]. Generally, the intensity of all these two diffraction peaks increased, implying an increase in coating crystallinity, gradually with increasing aluminum fraction.…”

Section: Micro-structural and Morphological Characterizationsupporting

confidence: 72%

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique

Tlili

Nasri²,

Nouveau

et al. 2010

Vacuum

View full text Add to dashboard Cite

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. The CrAlN coatings are a good alternative to conventional CrN coatings especially for high temperature oxidation-resistance applications. Different CrAlN coatings were deposited on silicon (100) by PVD (Physical vapor deposition) technique from two targets (chromium and aluminum) in a reactive nitrogen atmosphere at aluminum applied negative voltage (À300, À500, À700 and À900 V). The composition, structural, mechanical and thermal properties of the as-deposited coatings were systematically characterized by energy dispersive analysis of X-rays, X-ray diffraction, nanoindentation, and the ''Mirage effect'' experiments. The X-ray diffraction (XRD) data show that in general CrAlN coatings were crystallized in the cubic NaCl B1 structure, with the (1 1 1) and (2 0 0) diffraction peaks observed. Two-dimensional surface morphologies of CrAlN coatings were investigated by atomic force microscope (AFM). The results show that with increasing aluminum proportion the coatings became more compact and denser and their increased correspondingly, showing a maximum hardness of about 36 GPa (30 at% of Al) which is higher than that of CrN. Moreover, the results in this work demonstrate that the variation of aluminum fraction alter the resulting columnar grain morphology and porosity of the coatings. However, the thermal properties are greatly affected by these morphological alterations. The correlation between aluminum fraction in CrAlN coatings and its thermal properties revealed that the conductivity and the diffusivity are influenced primarily by size and shape distribution of the pores and secondarily by a decrease of the stitch parameter dimension.

show abstract

Section: Micro-structural and Morphological Characterizationsupporting

confidence: 72%

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique

Tlili

Nasri²,

Nouveau

et al. 2010

Vacuum

View full text Add to dashboard Cite

show abstract

“…In recent years, the industry requirements on high speed and dry applications at elevated temperatures have been devoted in numerous scientific and technological efforts due to the importance in applications where the temperature in the cutting tool edge can exceed 1000 ºC [1]. Tools and machine parts protected by hard coatings are able to operate at these extreme conditions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Silicon Addition on Microstructure and Mechanical Properties of Chromium and Titanium Based Coatings

Ardila-Téllez¹,

Sanchez

Téllez

2014

Fac. Ing.

View full text Add to dashboard Cite

<p>The changes in the microstructure, mechanical properties and residual stresses of AlTiN, AlTiSiN, AlCrN and AlCrSiN coatings, has been studied before and after annealing at 900 ºC and 1100 ºC, using scanning and transmission electron microscopy, along with nano-indentation and X-ray diffraction techniques. The As-deposited coatings show a columnar structure, with a crystallite size between 18 nm and 28 nm. Despite the silicon addition, no effect on the crystallite size refinement was observed.<br />However, the addition of silicon increases hardness, elastic modulus and compressive residual stresses. After annealing at 900 ºC, the crystallite size growth and the residual stress relaxes; therefore, the coating hardness decreases. At 1100 ºC, the oxide layers formed in AlTiN and AlTiSiN, which act as protective layers enhancing oxidation resistance; meanwhile, a complete oxidation of AlCrN and AlCrSiN coatings take place. The Titanium based coatings present some superior mechanical properties and oxidation resistance than the chromium based coatings at 900 ºC and 1100 ºC.</p>

show abstract

“…Another material that has seen use is (CrAl)N. It does not go through the same age hardening process as (TiAl)N, but is seen to have better oxidation resistance [81,85,[88][89][90][91][92]. (CrAl)N is also thermodynamically less unstable than (TiAl)N, allowing for solubility of larger amounts of Al before the onset of the hexagonal phase as well as the appearance of isostructural stability at low concentrations of Cr.…”

Section: Resultsmentioning

confidence: 99%

Theoretical understanding of stability of alloys for hard-coating applications and design

Lind¹

2015

Linköping Studies in Science and Technology. Dissertations

View full text Add to dashboard Cite

The performance of modern hard coating materials puts high demands on properties such as hardness, thermal stability and oxidation resistance. These properties not only depend on the chemical composition, but also on the structure of the material on a nanoscale. This kind of nanostructuring will change during use and can be both beneficial and detrimental as materials grown under non-equilibrium conditions transforms under heat treatment or pressure into other structures with significantly different properties. This thesis aims to reveal the physics behind the processes of phase stability and transformations and how this can be utilized to improve on the properties of this class of alloys. This has been achieved through the application of various methods of first-principles calculations and analysis of the results on the basis of thermodynamics and electronic structure theory.Within multicomponent transition metal aluminum nitride alloys (TMAlN) a number of studies have been carried out and presented here on ways of improving high temperature stability and hardness. Most (TMAl)N and TMN prefer a cubic B1 structure while AlN is stable in a hexagonal B4 phase, but for the purposes of hard coatings the metastable cubic B1 AlN phase, isostructural with the TMN phase is desired. It will be shown how the introduction of additional alloying components, such as Cr, into (TiAl)N changes the thermodynamic stability of phases so that new intermediary and metastable phases are formed during decomposition. In the case of such a (CrAl)N phase it is shown to have greater thermodynamic stability in the cubic phase than the pure AlN, resulting in improved high temperature hardness. Also, the importance of treating not just the binodal decomposition through the formation energy relative to end products but also the impact of spinodal decomposition from its second derivative due to the topology of formation energy surfaces is emphasized in the thesis. The impact of pressure on the AlN phase has also been studied through the calculation of a P-T diagram of AlN as part of a (TiAl)N alloy.During the study of chemical alloying of TM components into AlN the alloying of low concentrations of these TM were treated in great detail. What is generally referred to as the AlN phase in decomposition is not entirely pure and can be expected to contain traces of any alloying components, such as Ti and Cr or whatever other metals may be present. Low concentration alloying of Cr, on the order of 5-10% is also shown to be stable with regard to isostructural decomposition. Detailed analysis of the effect of Ti and Cr impurities in AlN has been carried out along with a systematic search of AlN alloyed with small amounts of other TM components. The impact of these impurities on the electronic structure and thermodynamic properties is analyzed and the general trends will be explained through the occupation of impurity states by d-like electrons.iv Theoretical treatment of such impurities is not straightforward however. AlN is an s-p semiconduct...

show abstract

Thermal stability of Al–Cr–N hard coatings

Cited by 246 publications

References 21 publications

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique

Effect of Silicon Addition on Microstructure and Mechanical Properties of Chromium and Titanium Based Coatings

Theoretical understanding of stability of alloys for hard-coating applications and design

Contact Info

Product

Resources

About