Eric Vancoille

Interrelationship between processing, coatingproperties and functional properties of steered arc physically vapour deposited (Ti,AI)N and (Ti,Nb)N coatings

Abstract In the framework of a European BRITE Project on “steered arc ion plating forthe development of new ternary and quaternary ceramic coatings for cutting and forming tools”, (Ti,Al)N and (Ti,Nb)N coatings were developed and optimized. The relation between bias voltage, N, pressure and composition of the coatings was established. Coating properties such as composition, crystal structure, lattice parameter, internal stress, Youngs modulus and hardness measured by nanoindentation were determined. The oxidation behaviour of (Ti,Al)N and (Ti,Nb)N was investigated with Auger electron spectroscopy. The performances of industrial TiN coatings and these new ternary coatings deposited on high speed steel substrates were compared in drill tests. (Ti,Al)N made by the steered arc appears to be more oxidation resistant than TiN and (Ti,Nb)N. Laboratory wear tests and field tests indicate that the interaction between workpiece and coated tool may give important clues as to the suitability of a coating type for a particular type of workpiece material.

Dry sliding wear of TiN based ternary PVD coatings

In order to understand the tribological characteristics of TiN, (Ti, Al)N, (Ti, Nb)N and Ti(C, N) coatings, ball-on-disc experiments were performed under dry sliding ambient conditions. The coefficient of friction and the wear resistance against a corundum counterbody were determined as a function of coating composition and sliding speed. The wear of the (Ti, Nb)N coatings was found to be comparable to that of the TiN coatings and this was related to the formation of a similar type of oxide in the tribo-contact. In the case of the (Ti, Al)N coatings, the wear volume increased markedly as the aluminium) in the coating increased, and the tribo-oxide formed was found to be Al2TiO5. Ti(C, N) coatings exhibited an extremely low wear against corundum because of the low coefficient of friction. A mild-oxidational wear model was found to give a qualitative fit to the experiments. Measuring the coating wear as a function of sliding speed opens the possibility of calculating the activation energy for tribo-oxidation processes of thin coatings.

Mechanical properties of heat treated and worn PVD TiN, (Ti, Al)N, (Ti, Nb)N and Ti(C, N) coatings as measured by nanoindentation

Abstract Steered arc ion plated TiN, (Ti 50 , Al 50 )N, (Ti 85 , Nb 15 )N and Ti(C 60 , N 40 ) coatings were heat treated in an inert argon atmosphere at temperatures up to 900°C. The hardness, Youngs modulus and plasticity of the coatings were measured with nanoindentation after heating. As the coatings were annealed at higher temperatures, the hardness decreased and the plasticity increased. X-ray diffraction of the coatings showed that this corresponds to a decrease in internal stress and a change of crystallographic texture. The nanohardness of the cutting edge of coated drills was also measured after these were used in AISI 4140 steel. Scanning electron microscopy demonstrated the presence of a silicate layer located near the cutting edge of (Ti 85 , Nb 15 )N coated drills. Nanoindentation showed that the mechanical signature of the surface film further away from the cutting edge corresponded to a heat-treated coating covered with an oxide layer.

Tribological and structural characterization of a physical vapour deposited TiC/Ti(C,N)/TiN multilayer

Abstract A physical vapour deposited TiC/Ti(C,N)/TiN multilayer was investigated and compared with a PVD TiN monolayer coating in a ball-on-disc test. Wear and friction against a corundum ball were measured as a function of time and sliding velocity. In these experiments, the coefficient of friction remained constant at 0.2 as long as the ball was sliding on TiC or intermidiate Ti(C,N) layers. When the TiN layer was reached, the coefficient of friction became unstable and rose to an average value of 1–1.5, which is characteristic for a TiN/Al 2 O 3 contact. Wear rates for the multilayer were found to be three to four times smaller as compared to the reference TiN. The multilayer morphology of the TiC/Ti(C,N)/TiN was revealed in a low-angle cross-section resulting from a prolonged ball-on-disc test. In that way, it was shown that the multilayer consisted of nine separate sublayers.

Evaluation of Metallization Options for Advanced Cu Interconnects Application

The traditional Cu interconnect barrier/seed process consisting of PVD-Ta based barrier/Cu-seed will reach its limit between 20 nm and 30 nm wide trench dimension. To extend Cu interconnect technology further, possible solutions such as PVD-RuTa, PEALD-Ru-based, CVD-Co, PVD/CVD-self-formed-MnSixOy and self-assembled monolayers (SAMs) are studied. It is shown that both PVD-RuTa and CVD-Co possess the so-called seed enhancement capability allowing Cu filling of narrow recesses. However, they exhibit limitations in terms of Cu-diffusion barrier efficiency, electromigration reliability and scalability. Despite, the concept of SAM [NH2-SAM(C3)] as Cu diffusion barrier is demonstrated, it requires maturity and compatibility within the process flow (e.g. adhesion with the Cu overlayer). Finally, it is considered that PEALD-Ru-based alloys and CVD-based MnSixOy films are serious candidates for sub-30 nm wide trench technologies because of their conformal nature and ability to act as an efficient Cu diffusion barrier in the range of 2 nm thickness.

Micro-Raman spectroscopy for the characterization of wear induced surface modifications on hard coatings

Micro-Raman spectroscopy can be a helpful tool in determining wear induced surface modifications due to its ability to identify compounds and measure internal stress in an area with a diameter as low as 1 pm. Micro-Raman spectroscopy is used here to characterize surface reactions, transfer layers and internal stress relaxation induced by wear processes for four different hard coatings: PVD TiN, solar beam oxidized TiN, CVD diamond and diamond-like carbon coatings. The Raman spectroscopic investigation of partially worn coatings has resulted in very specific information complementary to results that can be obtained with commonly used surface characterization techniques.

Mechanical Properties of Tin, (Ti,Al)N, (Ti,Nb)N and Ti(C,N) Coatings Measured by Nanoindentation

Ternary alloyed TiN based PVD coatings are second generation coatings for high speed cutting of abrasive alloys. In this respect, hardness is certainly one of the most interesting mechanical properties, but evaluating it is a challenge because of the limited coating thickness (2 to 3 μm). Therefore, nanoindentation was used to determine hardness and Youngs modulus of steered arc ion plated (Ti,Al)N and (Ti,Nb)N coatings with different compositions. It was found that the ternary coatings were harder and showed a higher Youngs modulus compared to the simple TiN. Since high temperatures develop during machining at increased speeds, the effect of a heat treatment on the mechanical properties of these coatings is worth investigating. So the hardness of TiN, (Ti 50 ,Al 50 )N, (Ti 85 ,Nb 15 )N and Ti(C 60 ,N 40 ) coatings was determined after a heat treatment under argon at temperatures up to 900 °C. It was observed that the hardness decreased as the coatings are annealed at progressively higher temperatures. X-ray diffraction showed that the internal stress decreases and the crystallographic texture of the coatings is modified.

Paper V (i) Modelling a Ball-on-Disk Experiment for the System 100Cr6 Steel Vs (Ti,X)N Coating

Friction and wear characteristics of PVD TiN, (Ti 50 ,Al 50 )N and (Ti 70 ,Nb 30 )N coated disks sliding against DIN 100Cr6 (AISI D3) hardened chromium steel balls were investigated. The coefficient of friction and the arm displacement were measured on-line whereas the worn-off volume of the ball after the test was optometrically determined. In most cases a reddish brown transfer layer of Fe and Fe 2 O 3 was left on the disk. The on-line measured friction and displacement were found to be a result of debris formation, trapping and ejection. In the steady state a dynamic equilibrium exists between particle formation (F), adhesion (A) and escape (E). It is suggested that the coefficient of friction originates mainly from the shear force between the particles in the third-body layer. The experiments show that care must be taken when interpreting the on-line measurements for studying the wear behaviour of (Ti,X)N coatings vs steel.