High Temperature microhardness of hard coatings produced by physical and chemical vapor deposition

doi:10.1016/0040-6090(87)90166-0

Thin Solid Films

Volume 153, Issues 1–3, 26 October 1987, Pages 19-36

https://doi.org/10.1016/0040-6090(87)90166-0 Get rights and content

Abstract

The microhardness of hard coatings of TiN and HfN prepared by chemical vapor deposition (CVD) and TiN, HfN, ZrN and TiAlN prepared by physical vapor deposition (PVD) were measured between room temperature and 1000°C. The microhardness of the PVD coatings was significantly higher than that of the CVD counterparts at room temperature but all microhardness values tended to converge at 1000°C. Higher N: Ti ratios were found in PVD TiN relative to CVD TiN. X-ray diffraction measurements indicated that the PVD coatings contained high residual compressive growth stresses associated with lattice distortion and very fine grain size, which were confirmed using transmission electron microscopy. Low residual stresses in high temperature CVD coatings are caused by thermal expansion mismatch between coating and substrate. Differences in grain morphology and crystal texture are attributed to varying conditions of energetic bombardment and deposition temperature in the several PVD methods employed. The faster decrease in microhardness with temperature in PVD coatings is caused by the high residual energy and finer grain size.

References (18)

J.E. Sundgren
Thin Solid Films
(1985)
J.E. Sundgren et al.
Thin Solid Films
(1983)
S. Kanamori
Thin Solid Films
(1986)
A.J. Perry et al.
Thin Solid Films
(1984)
B.O. Johansson et al.
J. Mater. Res.
(1986)
E. Torok et al.
Thin Solid Films
(1987)
P.K. Mehrotra et al.
B.M. Kramer et al.
J. Vac. Sci. Technol.
(1985)
B.M. Kramer
J. Vac. Sci. Technol.
(1986)

There are more references available in the full text version of this article.

Cited by (131)

Effect of thick film coating on scratch resistance of aluminium 6082-T6 alloy under varied loading conditions
2023, Materials Today: Proceedings
This experimental investigation is devoted to the analysis of computerized data of thick film coated aluminium 6082-T6 specimens under scratch test for different types of loads. Experimentation have been carried out on TiAl, WC-Co and NiCrAlY coated samples. For all the coated samples Ni-Cr bond coat has been used. The scratch width and scratch hardness of these coated samples were determined under constant load sets over fixed stroke length. Scratch test were carried out in accordance with the ASTM G-117 standards. Tests were also performed under step and ramp loads for the same stroke lengths to examine the nature of coated failure. Results of the scratch tests have shown that, the coating thickness and the range of loads play a significant role on the cohesive and adhesive nature of failure. It is identified that, for all type of loading, scratch hardness is found to be high in NiCrAlY coated samples. The nature of fracture and micro mechanism of fracture under scratch are precisely analyzed with the aid of SEM micrographs.
The influence of the H/E ratio on wear resistance of coating systems – Insights from small-scale testing
2022, Surface and Coatings Technology
The limit of applicability of the correlation between the ratio of hardness to elastic modulus (H/E) of coating systems and their wear resistance has been explored. Experimental approaches to determine accurate H/E values by nanoindentation are discussed and best practice recommendations summarised. Small-scale tribo-testing has been used to simplify complex wear conditions, and the role of contact severity and damage tolerance studied to determine why and when coating optimisation strategies are effective. Case studies show the importance of relatively low coating elastic modulus in reducing tensile stresses in sliding/abrasive contact. This may be a key factor in why coating design for optimised H/E and resistance to plastic deformation, H³/E², can be more effective than aiming for extremely high coating hardness since that is typically accompanied by high coating stiffness. The influence of substrate ductility and load support on the damage tolerance of the coating system in impact tests has been investigated by testing at different contact size. Results show that mechanical and microstructural factors should not be considered in isolation. The role of coating microstructural design and temperature on optimising coating performance in high speed machining is investigated.
Deformation behaviour of TiN and Ti–Al–N coatings at 295 to 573 K
2019, Thin Solid Films
Citation Excerpt :
The temperature variation of hardness of the magnetron sputtered TiN coating (TiNcoating) is shown in Fig. 1a, along with data from SC-TiNbulk [19] for comparison. For the TiN coating, the hardness dropped from 22.5 ± 0.7 GPa at 295 K to 13.0 ± 1.2 GPa at 573 K. Over the tested temperature range, 295 to 573 K, the TiN coating displayed a very similar hardness response to the SC-TiNbulk, which exhibited a hardness drop from 21.2 ± 0.5 GPa at 295 K to 12.7 ± 0.4 GPa at 573 K. Also included in the figure are the data obtained by Quinto et al. [23], Quinto [24] and Jindal et al. [25] from Vickers indentation of magnetron sputter deposited TiN coatings, which show a similar trend of the hardness decrease with temperature. The influence of Al substituting for Ti in the TiN lattice on the hardness of magnetron sputtered Ti1-xAlxN (with x = 0, 0.34, 0.52, 0.62) coatings, at various temperatures, is shown in Fig. 1b.
Temperature-dependent nanoindentation testing was employed to investigate the deformation behaviour of magnetron sputtered (100) TiN and Ti_1-xAl_xN (x = 0.34, 0.52, 0.62) coatings in the temperature range from 295 to 573 K. The maximum temperature is sufficiently below the deposition temperature of 773 K to guarantee for stable microstructure and stress state during testing. The TiN coating displayed the same hardness as bulk single crystal (SC) TiN_bulk. The addition of aluminium to TiN (to form single-phase face centred cubic structured Ti_1-xAl_xN coatings) increased the room temperature hardness due to increased bond strength, lattice strain and higher activation energy for the dislocation slip. For coatings with a low aluminium content, Ti_0.66Al_0.34N, the decrease in hardness with temperature was similar to the TiN coating and SC-TiN_bulk. In contrast, the hardness of coatings with moderate, Ti_0.48Al_0.52N, and high, Ti_0.38Al_0.62N, aluminium contents varied little up to 573 K. Thus, the Ti_1-xAl_xN matrix is mechanically more stable at elevated temperatures than its TiN relative, by providing a lower decrease in lattice resistance to the dislocation flow with increasing temperature. The findings suggest that the addition of Al to TiN (to form Ti_1-xAl_xN solid solutions) not only improves the hardness but also leads to stable hardness with temperature, and emphasizes the importance of bonding states and chemical fluctuations, next to structure and morphology of the coatings that develop with changing the chemistry.
Elevated temperature micro-impact testing of TiAlSiN coatings produced by physical vapour deposition
2019, Thin Solid Films
Citation Excerpt :
This is due to a combination of factors which act in synergy including improved oxidation resistance, thermal stability, age-hardening through spinodal decomposition and more protective tribofilm formation in comparison to binary nitrides such as TiN or CrN [12–14]. Despite this, hot microhardness and elevated temperature nanoindentation studies have shown that their hot hardness can decrease dramatically in comparison to room temperature measurements [15–19]. More advanced multilayer coatings and quaternary compositions are being developed with improved properties such as enhanced high temperature mechanical properties and wear resistance [19–36].
A high temperature micro-impact test has been developed to assess the fracture resistance of hard coatings under repetitive dynamic high strain rate loading at elevated temperatures. The test was used to study the temperature dependence of the resistance to micro-scale impact fatigue of TiAlSiN coatings on cemented carbide at 25–600 °C. Nanoindentation and micro-scratch tests were also performed over the same temperature range. The results of the micro-impact tests were dependent on the impact load, coating microstructure, coating and substrate mechanical properties, and their temperature dependence. At higher temperatures there was a change in failure mechanism from fracture-dominated to plasticity-dominated behaviour under the cyclic loading conditions. This was attributed to coating and substrate softening.
Deposition and characterization of (Ti, Al)N coatings deposited by thermal LPCVD in an industrial reactor
2019, Surface and Coatings Technology
Citation Excerpt :
Above this value, a hardness drop is observed, with a value of 20.0 GPa for Ti0.16Al0.84N. Finally, hardness seems to increase slightly for Ti0.14Al0.86N. According to the low Al content in the Ti0.92Al0.08N coating, its hardness (26.6 GPa) seems to be quite high compared to the typical values reported for fcc-TiN coatings (about 20 GPa) [18,21]. This relatively high value can be attributed to the nanolamellae microstructure.
The increased need for protecting cutting tools has led to the development of more and more efficient coatings. Ti-Al-N is one of the most studied systems in the hard coating industry due to the high hardness and good oxidation resistance of Ti_1−xAl_xN coatings. The development of LPCVD processes has led to the discovery of new microstructures and morphologies. In this study, we discuss the microstructural and morphological changes caused by varying the aluminum content in films deposited by low pressure thermal CVD in an industrial reactor at low carrier gas flow and relatively high pressure (>4 kPa). Coatings were characterized using FE-SEM, XRD and TEM analysis, revealing the growth of nanolamellae with modulated Al and Ti contents for the lowest Al containing coatings. The coatings with the highest Al contents were also found to show particular cube-shaped grains with a micromodulation of composition. Experimental Al content values are higher than the calculated one and their evolutions with the AlCl₃/(AlCl₃ + TiCl₄) molar ratio are similar. The hardness and oxidation resistance were characterized and compared with available data in literature. Higher hardness is obtained for coatings having an Al content up to x = 0.65 and a hardness drop is found for higher Al contents. The oxidation resistance of the coatings rises continuously with an increasing Al content.
Influence of annealing on the microstructure and mechanical properties of MTCVD TiC<inf>0.79</inf>N<inf>0.21</inf> coating
2018, Vacuum
TiC_0.79N_0.21 coating was deposited on WC-Co cemented carbide by moderate temperature chemical vapour deposition technique and then annealed in vacuum or air in the temperature range of 700–900 °C for 1 h. The morphology, composition, phase component, residual stress, hardness and plastic deformation resistance of the coating before and after annealing were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analyzer (EPMA), X-ray diffractometer (XRD) and nano-indentator. The results show that after annealing in low vacuum, the grain boundaries of the coating surface are still clearly visible and small capsule or granular oxide particles are uniformly distributed on the columnar surfaces of the coating. Coarse irregular particles enriched with W element are randomly located at the grain boundaries. After annealing in air, the coating is, however, oxidized to rutile TiO₂ and oxidation rate increases with temperature. Dramatic coating oxidation is observed at 900 °C. With the increase of temperature, the residual tensile stress increases and compressive stress decreases after annealing in air and vacuum, respectively. The hardness and plastic deformation resistance on the cross section of coating are improved with temperature after vacuum annealing while opposite tendency is obtained for annealing in air.

View all citing articles on Scopus

^☆: Paper presented at the 14th International Conference on Metallurgical Coatings, San Diego, CA, U.S.A., March 23–27, 1987.

View full text

High Temperature microhardness of hard coatings produced by physical and chemical vapor deposition☆

Abstract

Thin Solid Films

Thin Solid Films

Thin Solid Films

Thin Solid Films

J. Mater. Res.

Thin Solid Films

J. Vac. Sci. Technol.

J. Vac. Sci. Technol.