Control of Tribological Characteristics of Wear-Resistant AlCrBN Coatings by Nanoscratch Testing
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-07-02 |
| Journal | Devices and Methods of Measurements |
| Authors | V. A. Lapitskaya, T. A. Kuznetsova, B. WarcholiĆski, Anastasiya Khabarava, T. V. Hamzeleva |
| Institutions | Belarusian National Technical University, Powder Metallurgy Institute |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research validates the use of nanoscratch testing as a high-precision quality control method for wear-resistant AlCrBN coatings deposited via cathodic arc evaporation.
- Method Validation: Nanoscratch testing (micro/nanolevel tribotesting) is demonstrated as an effective, rapid alternative to standard macrotests for characterizing AlCrBN coatings.
- Defect Elimination: The method successfully isolates tribological measurements from the influence of characteristic microparticles (microdroplets) inherent to the cathodic arc process, providing true coating friction values.
- Performance Improvement (Pressure): Increasing nitrogen pressure (pN2) from 2 Pa to 5 Pa resulted in a significant decrease in the micro-friction coefficient (CoF) from 0.087 to 0.036.
- Performance Improvement (Bias): Increasing the substrate bias voltage (UB) from -50 V to -150 V also reduced the micro-CoF from 0.077 to 0.041.
- Current Insensitivity: Varying the cathode current (Ic) from 80 A to 100 A had a negligible effect on the micro-CoF (0.047 vs. 0.045).
- Scale Difference: The micro-CoF values determined by nanoscratch testing (0.036-0.087) were found to be approximately an order of magnitude lower than those obtained from traditional macrotests (0.65-0.77).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Coating Material | AlCrBN | N/A | Wear-resistant nitride coating |
| Coating Thickness | 4.4 ± 0.1 | ”m | Deposited layer thickness |
| Cathode Composition | Al50Cr30B20 | % | Alloy target material |
| Deposition Temperature | 350 | °C | Constant process temperature |
| Substrate Material | 4H13 (X39Cr13) | DIN standard | Martensitic stainless steel |
| Substrate Roughness (Ra) | 0.02 | ”m | Polished prior to deposition |
| Nanoscratch Indenter Radius | 226 | nm | Spherical diamond tip |
| Nanoscratch Load | 500 | ”N | Constant normal load |
| Nanoscratch Cycles | 100 | cycles | Reciprocating test duration |
| Scratch Length | 5 | ”m | Length of single scratch track |
| Minimum Micro CoF | 0.036 ± 0.004 | N/A | Achieved at 5 Pa N2 pressure |
| Maximum Macro CoF | 0.77 ± 0.01 | N/A | Reference value from macrotests [12] |
| N2 Pressure Range | 2 to 5 | Pa | Varied deposition parameter |
| Substrate Bias Range | -50 to -150 | V | Varied deposition parameter |
| Cathode Current Range | 80 to 100 | A | Varied deposition parameter |
| AFM Roughness Ra (Min) | 14.8 ± 0.7 | nm | Measured in particle-free areas (3x3 ”m2) |
Key Methodologies
Section titled âKey MethodologiesâThe AlCrBN coatings were synthesized using the Cathodic Arc Evaporation method, followed by detailed characterization and nanoscratch tribotesting.
- Deposition Setup: Coatings were deposited in a TINA 900 M setup using Al50Cr30B20 alloy cathodes onto polished martensitic stainless steel (4H13) substrates at a constant temperature of 350 °C.
- Parameter Matrix: Six different coating samples were produced by systematically varying the key deposition parameters:
- Nitrogen pressure (pN2): 2 Pa, 4 Pa, 5 Pa.
- Substrate bias voltage (UB): -50 V, -100 V, -150 V.
- Cathode current (Ic): 80 A, 100 A.
- Surface Characterization (Macro): Surface roughness (Ra, Rq, Rz) was measured using a Mitutoyo Surftest SJ-210 contact profilometer over 2.5 mm profiles, capturing the influence of microparticles.
- Surface Characterization (Nano): Surface morphology and nanoroughness were analyzed using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM, Bruker Dimension FastScan) in Peak-Force QNM mode.
- Nanoscratch Testing: Microtribological properties were determined using a Hysitron 750Ubi nanoindenter equipped with a spherical diamond tip (radius 226 nm, 60° apex angle).
- Test Protocol: Multi-cycle reciprocating tests were performed (100 cycles) under a constant load of 500 ”N, with a scratch length of 5 ”m.
- Data Analysis: Testing was specifically conducted on particle-free areas (identified via SEM/AFM) to eliminate microdroplet influence. The average friction coefficient (CoF) was calculated, excluding the initial 10 cycles to mitigate the effect of initial surface topography.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings regarding the precise control and validation of tribological properties of AlCrBN coatings are highly relevant to industries requiring superior wear resistance and low friction performance.
- Precision Machining Tools: AlCrBN coatings are widely used on cutting tools (e.g., end mills, inserts) for dry machining and high-speed cutting of difficult materials (e.g., hardened steels, nickel alloys). The ability to precisely control CoF ensures optimal tool life and chip flow.
- High-Performance Components: Coating critical components in automotive, aerospace, and energy sectors, such as engine valves, bearings, and gears, where low friction and high thermal stability are essential.
- Micro-Electro-Mechanical Systems (MEMS): For micro-scale devices where friction and wear must be minimized at the nanoscale, the nanoscratch method provides necessary quality assurance for thin film performance.
- PVD/Cathodic Arc Process Optimization: The research provides direct feedback on how deposition parameters (N2 pressure, bias voltage) influence the intrinsic tribological quality of the coating, enabling manufacturers to fine-tune recipes for specific CoF targets.
- Quality Control and R&D: Implementing nanoscratch testing as a standard, rapid, and non-destructive quality control method for PVD coating batches, replacing time-consuming and destructive macro-wear tests.
View Original Abstract
In recent years, high-precision probe methods have been increasingly used to control the surface microstructure, mechanical and tribological properties of coatings instead of standard methods. The aim of the work was to study the tribological characteristics of the wear-resistant coatings (using the example of AlCrBN coatings deposited with changes in nitrogen pressure, substrate bias voltage and cathode current) at the microand nanolevel using the nanoscratch testing (nano-scratching) method. The nanoscratch testing method is a non-standard method of tribotesting the wear-resistant coatings and is based on the reciprocating movement of a spherical diamond indenter with a curvature radius of 226 nm on the surface (under a certain load). It was found that the friction coefficient decreases from 0.087 to 0.036 for coatings deposited with an increase in pressure from 2 to 5 Pa. When the bias voltage on the substrate changes from -50 to -150 V, the friction coefficient decreases from 0.077 to 0.041 and when the cathode current changes from 80 to 100 A, the friction coefficient remains virtually unchanged. The use of this method made it possible to perform multi-cycle tribotesting of the AlCrBN coatings, determine the average values of the friction coefficient, and completely eliminate the influence of microparticles (the characteristic defects for coatings deposited by the cathodic arc method) on the measurements. Thus, the effectiveness of the nanoscratch testing (nanoscratching) as a method for the control wear-resistant coatings is demonstrated.