TiAlSiN Nanocomposite Coatings Research Articles

Scratch response and tribological properties of TiAlSiN coatings deposited by reactive deep oscillation magnetron sputtering

TiAlSiN nanocomposite coatings were deposited using deep oscillation magnetron sputtering with various nitrogen flow ratio (fN2) of 0%–20%. The increase of fN2 promotes phase separation from a single crystallographic TiAlSi to nc-(Ti,Al)N/a-Si3N4 phase. The introduce of N content leads to the formation of refined grain size, smooth morphologies and dense microstructure. Ti0.15Al0.39Si0.07N0.39 coatings with (Al + Si)/Ti ratio of 2.9 deposited at fN2 = 10% reach the highest hardness of 32.8 GPa, H/E* of and 0.0837 and H3/E*2 of 0.23. The introduce of N leads to failure mode changing from brittle tensile cracking (through-thickness cracking) to buckle spallation (interfacial failure). Ti0.15Al0.39Si0.07N0.39 coatings with highest H, H/E* and H3/E*2 ratios show buckling failure with high LC1 of 25.4 N and LC3 of 43.6 N. Correspondingly, Ti0.15Al0.39Si0.07N0.39 coatings are subjected to oxidation wear with low coefficient of friction of 0.41 and specific wear rate of 0.39 × 10−6 mm3 N−1 m−1.

Improved Adhesion of TiAlSiN Nanocomposite Coatings on Cemented Carbide Substrate by Pre-Implantation

TiAlSiN coatings were deposited on YT 15 cemented carbide substrate by reactive direct current magnetron sputtering (DCMS) in a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The pre-implantation step and the coating deposition were carried out in the same experimental facility. In this article the effects of pre-implantation of several different elements (N, C, and O) were investigated. The adhesion strength, hardness, micro-structure, element concentration, depth profile, and the formation of coatings after the PIII experiments were characterized by a wide variety of techniques such as Rockwell indentation, scratch test, nano-indentation measurement, X-ray diffraction, energy dispersive spectroscopy, and Auger electron spectroscopy. The results showed that the adhesive strength of TiAlSiN coatings was significantly improved on samples pre-implanted with N and O whereas only slightly improved with pre-implantation of C. Additionally, the microstructure and mechanical properties of the TiAlSiN coatings were also altered through pre-implantation. The improved adhesion could be explained by the grain refinement and surface energy enhancement of the substrate by pre-implantation.

Flexible hard TiAlSiN nanocomposite coatings deposited by modulated pulsed power magnetron sputtering with controllable peak power

TiAlSiN nanocomposite coatings were deposited by modulated pulsed power magnetron sputtering (MPPMS) with the varied peak power from 24.8 to 56.8 kW. The coatings had a typical nc-TiAlN/a-Si3N4 nanocomposite structure. The microstructure of the coatings changed from a columnar structure (Zone I in Thornton's Model) at 24.8 kW and 35.2 kW to a dense glassy-like structure (Zone T) at 44.6 kW and 56.8 kW. With increasing peak power from 24.8 to 56.8 kW, the hardness increased from 23.6 to 31.3 GPa, the H/E⁎ changed from 0.079 to 0.091, elastic recovery (We) increased from 50.1% to 57.4%, and compressive macrostress (σ) changed from −0.16 to −1.59 GPa. Fracture toughness (KIC) of the coatings was measured by the indentation test with a Vickers diamond indenter at the load L of 500 mN and 1000 mN. KIC increased from 0.96 to 1.77 MPa∙m1/2 with the peak power from 24.8 to 44.6 kW, except for no fracture at the highest peak power of 56.8 kW. The highest hardness, H/E⁎ ratio and elastic recovery of 31.3 GPa, 0.091, 57.4% with the macrostress of −1.59 GPa were obtained at the peak power of 56.8 kW. The enhanced toughness of TiAlSiN nanocomposite coatings was obtained at peak power of 44.6 kW and 56.8 kW, which was attributed to dense structure in the Zone T at high peak power. Effect of the bombarding energy (Ebi) and surface mobility (D) of the incident species on Zone T structure was explained by the electron densities and temperature, and number densities of Ti and Al sputtered species simulated using a global plasma model. The critical parameter of structural transformation from a columnar structure to a dense glassy-like structure is the increase of bombarding energy E and mobility of species D. The flexible and hard TiAlSiN nanocomposite coatings were deposited by MPPMS at higher peak power.

Analysis of TiAlSiN coatings deposited by reactive magnetron sputtering under high-current ion assistance

TiAlSiN nanocomposite coatings are obtained by the reactive magnetron sputtering of one-component targets with a widely varying (5–25) ratio of the ion current density j i to the atomic flux density j n on the sample surface. The plasma in the deposition chamber is generated by a broad (80 cm2) low-energy (100 eV) electron beam. The beam current is varied from 5 to 30 A, which makes it possible to adjust j i in the range of 1.8 to 9 mA/cm2. It is shown that an increase in the ratio j i /j n is accompanied by a nonmonotonic variation in the hardness and texture of the coatings under the action of internal stresses. It is established that exceeding the value j i /j n at which the maximum hardness of the coating is reached (43 GPa) leads to the relaxation of intrinsic stresses and a reduction in the hardness to 36 GPa.

Effect of bias voltage on TiAlSiN nanocomposite coatings deposited by HiPIMS

TiAlSiN nanocomposite coatings were deposited onto cemented carbide (WC-10wt.%, Co) substrates by high power impulse magnetron sputtering (HiPIMS). The effect of substrate bias voltage on plasma discharge characterization of HiPIMS, element concentration, deposition rate, microstructure, surface/cross-sectional morphology, hardness and adhesion strength of coatings were studied. Compared with those deposited with direct current magnetic sputtering (DCMS), HiPIMS-deposited TiAlSiN coatings show improvements in some properties, including the surface roughness, the grain size, the hardness and adhesion strength, but a decrease in the deposition rate. When the bias voltage increases, the discharge current rose up from 118A to 165A. HiPIMS-deposited TiAlSiN coatings show a shift of the preferred crystallographic orientation from (220) to (200) and decreases in surface roughness from 14.1nm down to 7.4nm and grain size from 10.5nm to 7.4nm. Meanwhile, a change in crystal morphology from columnar to equiaxial and a grain refinement, as well as an increase of hardness from 30GPa up to 42GPa of those TiAlSiN coatings were observed with the increasing bias voltage and a decrease in adhesion strength from HF2 to HF5 of those coatings were revealed by indentation adhesion test.

Effect of Ti content on the microstructure and mechanical properties of TiAlSiN nanocomposite coatings

TiAlSiN coatings has been proposed and studied because of their desirable properties in hardness and coating-substrate adhesion. Further improvement of their performance can be achieved by better understanding the effect of the concentration of each element on the microstructure and mechanical properties of the coatings. In this paper, the TiAlSiN coatings with different Ti content were deposited by reactive DC magnetron sputtering method. The microstructure and mechanical properties of the coatings were analyzed by energy dispersive spectroscopy, X-ray diffraction, transmission electron microscope, scanning electron microscope, nano-indentor and Rockwell indentation tester. The results reveal that TiAlSiN coatings consisted of amorphous phase and crystalline phase. With a Ti content of 63at.%, as well as a Si content of 7at.%, a super-hard TiAlSiN coating with a nanoindentation hardness of 66GPa was achieved. What is more, in contrast to the well-described super-hard nanocomposite TiAlSiN coatings, another “nanocomposite” microstructure coating with a Ti content of 29at.% in which the amorphous phase is wrapped in a crystalline phase was identified, with a comparatively low hardness value of 20GPa. The highest adhesion strengths with a Rockwell indentation classes HF2 was achieved for a coating with a Ti content of 63 or 65at.%.

Effect of microstructure on mechanical and tribological properties of TiAlSiN nanocomposite coatings deposited by modulated pulsed power magnetron sputtering

TiAlSiN nanocomposite coatings were deposited in a closed field unbalanced magnetron sputtering system by reactive sputtering from Ti0.475Al0.475Si0.05 targets using modulated pulsed power magnetron sputtering (MPPMS) under a floating substrate bias. The ratio of the nitrogen flow rate to the total gas flow rate (fN2) was varied from 0 to 40%. The application of MPPMS as sputtering sources was aimed at generating a high ionization degree of the sputtered material and a high plasma density by using a pulsed high power approach. When fN2=0%, an amorphous-like structure Ti0.479Al0.454Si0.066 coating was deposited with a hardness of 10GPa. When nitrogen was added, an optimized nanocomposite structure of nc-TiAlN/a-Si3N4 formed in the TiAlSiN coating deposited at fN2=10%, in which 5–10nm TiAlN nanocrystallites were embedded in a 2–3nm thick amorphous Si3N4 matrix. As the fN2 was increased up to 40%, the elementary composition of the coatings remained almost the same, but the grain size of nanocrystallites approached to 10–20nm and the AlN phase gradually precipitated. A maximum hardness (H) of 33.2GPa, a hardness to the elastic modulus (E) ratio of 0.081 and an H3/E*2 ratio of 0.19GPa were found in the coating deposited at fN2=10%. The friction coefficient of the TiAlSiN coatings was around 0.8–0.9 as sliding against a Si3N4 counterpart under a normal load of 0.5N. A wear rate of 2.0×10−5mm3N−1m−1 was measured in the TiAlSiN coatings deposited at fN2=20–40%. As only a low residual stress is found in the TiAlSiN coatings, we consider the complete phase separation is responsible for the enhanced mechanical and tribological properties of the nc-TiAlN/a-Si3N4 nanocomposite coatings.

Microstructure and mechanical properties of TiAlSiN nano-composite coatings deposited by ion beam assisted deposition

TiAlSiN nano-composite coatings with Silicon contents from 4.1 to 23.9 at.% were deposited on Silicon wafers. The nanohardness, microstructure, and adhesion force of the coatings were deeply affected by Silicon contents. The TiAlSiN with 9.0 at.% Silicon has a maximum hardness of 40.9 GPa, a highest adhesion force of 67 N and a lowest friction coefficient of 0.5. Microstructures show that Silicon doping increases the hardness of coating due to solid solution hardening effect and grain boundary enhancement effect. The amorphous Si3N4 matrix, which contains (Ti,Al)N nano-crystals, is formed as the Silicon content is increased. The matrix contributes to the nano-hardness and helps to resist surface oxidization. Especially, the matrix induces low surface roughness and decreases the friction coefficient.

Microstructure Controlling and Properties of TiAlSiN Nanocomposite Coatings Deposited by Modulated Pulsed Power Magnetron Sputtering

Microstructure Controlling and Properties of TiAlSiN Nanocomposite Coatings Deposited by Modulated Pulsed Power Magnetron Sputtering

Influence of oxidation on the structural and mechanical properties of TiAlSiN coatings synthesized by multi-plasma immersion ion implantation and deposition

TiAlSiN nanocomposite and TiN coatings were synthesized by multi-plasma immersion ion implantation and deposition. The structure, hardness and tribological properties of both coatings oxidized at 800 °C were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, nano-indentation and ball-on-disk tests. The results show that the TiN coating was oxidized almost completely after air exposure at 800 °C. Except for a thin oxidized layer formed on the top surface containing TiO 2, Al 2O 3 and SiO 2, the cross section of the TiAlSiN coating remained in its original configuration after oxidation. Analysis revealed that the oxidized layer remained in a similar structure as before oxidation, which is TiO 2 nanocrystals embedded in an amorphous SiO 2 matrix. The hardness results show that the TiAlSiN coating after oxidation maintained a similar hardness as the un-oxidized coating. In addition, the TiAlSiN coating also showed a high wear resistance at 800 °C.

Influence of Si content on structure and mechanical properties of TiAlSiN coatings deposited by multi-plasma immersion ion implantation and deposition

TiAlSiN nanocomposite coatings were prepared by multi-plasma immersion ion implantation and deposition (MPIIID). The chemical composition, microstructure and mechanical properties of these coatings were investigated by energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nano-indentation and scratch tests. XRD patterns reveal that the main reflection in the as-deposited coating corresponds to a strong TiN (200) preferred orientation. XPS results show that AlN, Si 3N 4, Al 2O 3 and Ti 2O 3 are also formed in the coating. Comparing with the TiN coating, when the Si content in the coating is 0.9%, the film shows an increased hardness of 32 GPa, while its fracture toughness and adhesion strength are weak. When the Si content is increased to 6.0%, the coating exhibits a super hardness of 57 GPa as well as excellent fracture toughness and adhesion strength.

Deposition and characterization of TiAlSiN nanocomposite coatings prepared by reactive pulsed direct current unbalanced magnetron sputtering

This work reports the performance of high speed steel drill bits coated with TiAlSiN nanocomposite coating at different Si contents (5.5–8.1 at.%) prepared using a four-cathode reactive pulsed direct current unbalanced magnetron sputtering system. The surface morphology of the as-deposited coatings was characterized using field emission scanning electron microscopy. The crystallographic structure, chemical composition and bonding structure were evaluated using X-ray diffraction, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, respectively. The corrosion behavior, mechanical properties and thermal stability of TiAlSiN nanocomposite coatings were also studied using potentiodynamic polarization, nanoindentation and Raman spectroscopy, respectively. The TiAlSiN coating thickness was approximately 2.5–2.9 μm. These coatings exhibited a maximum hardness of 38 GPa at a silicon content of approximately 6.9 at.% and were stable in air up to 850 °C. For the performance evaluation, the TiAlSiN coated drills were tested under accelerated machining conditions by drilling a 12 mm thick 304 stainless steel plate. Under dry conditions the uncoated drill bits failed after drilling 50 holes, whereas, TiAlSiN coated drill bits (Si = 5.5 at.%) drilled 714 holes before failure. Results indicated that for TiAlSiN coated drill bits the tool life increased by a factor of more than 14.