High Temperature Mechanical Testing Application Notes - NANOVEA: Advanced Profilometers, Tribometers, Nanoindenters, and Scratch Testers for Materials Testing

High Temperature Scratch Hardness using a Tribometer

nanovea — Thu, 14 Jul 2022 16:56:16 +0000

HIGH TEMPERATURE SCRATCH HARDNESS

USING A TRIBOMETER

Prepared by

DUANJIE, PhD

INTRODUCTION

Hardness measures the resistance of materials to permanent or plastic deformation. Originally developed by a German mineralogist Friedrich Mohs in 1820, scratch hardness test determines the hardness of a material to scratches and abrasion due to friction from a sharp object¹. The Mohs’ scale is a comparative index rather than a linear scale, therefore a more accurate and qualitative scratch hardness measurement was developed as described in ASTM standard G171-03². It measures the average width of the scratch created by a diamond stylus and calculates the scratch hardness number (HSP).

IMPORTANCE OF SCRATCH HARDNESS MEASUREMENT AT HIGH TEMPERATURES

Materials are selected based on the service requirements. For applications involving significant temperature changes and thermal gradients, it is critical to investigate the mechanical properties of materials at high temperatures to be fully aware of the mechanical limits. Materials, especially polymers, usually soften at high temperatures. A lot of mechanical failures are caused by creep deformation and thermal fatigue taking place only at elevated temperatures. Therefore, a reliable technique for measuring hardness at high temperatures is in need to ensure proper selection of the materials for high temperature applications.

MEASUREMENT OBJECTIVE

In this study, the NANOVEA T50 Tribometer measures scratch hardness of a Teflon sample at different temperatures from room temperature to 300ºC. The capability of performing high temperature scratch hardness measurement makes the NANOVEA Tribometer a versatile system for tribological and mechanical evaluations of materials for high temperature applications.

NANOVEA

T50

TEST CONDITIONS

The NANOVEA T50 Free Weight Standard Tribometer was used to perform the scratch hardness tests on a Teflon sample at temperatures ranging from room temperature (RT) to 300°C. Teflon has a melting point of 326.8°C. A conical diamond stylus of apex angle 120° with tip radius of 200 µm was used. The Teflon sample was fixed on the rotative sample stage with a distance of 10 mm to the stage center. The sample was heated up by an oven and tested at temperatures of RT, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C.

TEST PARAMETERS

of the high temperature scratch hardness measurement

NORMAL FORCE	2 N
SLIDING SPEED	1 mm/s
SLIDING DISTANCE	8mm per temp
ATMOSPHERE	Air
TEMPERATURE	RT, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C.

RESULTS & DISCUSSION

The scratch track profiles of the Teflon sample at different temperatures are shown in FIGURE 1 in order to compare the scratch hardness at different elevated temperatures. The material pile-up on the scratch track edges forms as the stylus travels at a constant load of 2 N and ploughs into the Teflon sample, pushing and deforming the material in the scratch track to the side.

The scratch tracks were examined under the optical microscope as shown in FIGURE 2. The measured scratch track widths and calculated scratch hardness numbers (HSP) are summarized and compared in FIGURE 3. The scratch track width measured by the microscope is in agreement with that measured using the NANOVEA Profiler – the Teflon sample exhibits a wider scratch width at higher temperatures. Its scratch track width increases from 281 to 539 µm as the temperature elevates from RT to 300oC, resulting in decreased HSP from 65 to 18 MPa.

The scratch hardness at elevated temperatures can be measured with high precision and repeatability using the NANOVEA T50 Tribometer. It provides an alternative solution from other hardness measurements and makes NANOVEA Tribometers a more complete system for comprehensive high-temperature tribo-mechanical evaluations.

FIGURE 1: Scratch track profiles after the scratch hardness tests at different temperatures.

FIGURE 2: Scratch tracks under the microscope after the measurements at different temperatures.

FIGURE 3: Evolution of the scratch track width and scratch hardness vs. the temperature.

CONCLUSION

In this study, we showcase how the NANOVEA Tribometer measures the scratch hardness at elevated temperatures in compliance to ASTM G171-03. The scratch hardness test at a constant load provides an alternative simple solution for comparing the hardness of materials using the tribometer. The capacity of performing scratch hardness measurements at elevated temperatures makes the NANOVEA Tribometer an ideal tool for evaluating the high temperature tribo-mechanical properties of materials.

The NANOVEA Tribometer also offers precise and repeatable wear and friction testing using ISO and ASTM compliant rotative and linear modes, with optional high temperature wear, lubrication and tribo-corrosion modules available in one pre-integrated system. Optional 3D non-contact profiler is available for high resolution 3D imaging of wear tracks in addition to other surface measurements such as roughness.

1 Wredenberg, Fredrik; PL Larsson (2009). “Scratch testing of metals and polymers: Experiments and numerics”. Wear 266 (1–2): 76
2 ASTM G171-03 (2009), “Standard Test Method for Scratch Hardness of Materials Using a Diamond Stylus”

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Precise Localized Glass Transition with Nanoindentation DMA

nanovea — Tue, 14 May 2019 16:14:41 +0000

Precise Localized Glass Transition with Nanoindentation DMA

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Imagine a scenario where a bulk sample is uniformly heated at a constant rate. As a bulk material heats up and approaches its melting point, it will start to lose its rigidity. If periodic indentations (hardness tests) are conducted at the same target force, the depth of each indent should be constantly increasing since the sample is becoming softer (see figure 1). This continues until the sample begins to melt. At this point, a large increase in the depth per indent will be observed. Using this concept, phase change in a material can be observed by using dynamic oscillations with a fixed force amplitude and measuring its displacement, i.e. Dynamic Mechanical Analysis (DMA). Read about Precise Localized Glass Transition!

Stress Relaxation Measurement using Nanoindentation

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NOW, LET'S TALK ABOUT YOUR APPLICATION

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ASTM D7187 Temperature Effect Using Nanoscratching

nanovea — Thu, 29 Jun 2017 16:04:10 +0000

ASTM D7187, the resistance of the paint to scratch and mar plays a vital role in its end use. Automotive paint susceptible to scratches makes it difficult and costly to maintain and repair. Different coating architectures of the primer, basecoat, and clearcoat have been developed to achieve the best scratch/mar resistance. Nanoscratch testing has been developed as a standard test method to measure the mechanistic aspects of scratch/mar behavior of paint coatings as described in ASTM D7187. Different elementary deformation mechanisms, namely elastic deformation, plastic deformation and fracture, occur at different loads during the scratch test. It provides a quantitative assessment of the plastic resistance and fracture resistance of the paint coatings.

ASTM D7187 Temperature Effect Using Nanoscratching

The post ASTM D7187 Temperature Effect Using Nanoscratching appeared first on NANOVEA: Advanced Profilometers, Tribometers, Nanoindenters, and Scratch Testers for Materials Testing.

Teflon Mechanical Properties at High Temperature

nanovea — Wed, 27 Jul 2016 20:06:33 +0000

At elevated temperatures, heat changes teflon mechanical properties such as the hardness and viscoelasticity, which may result in mechanical failures. A reliable measurement of the thermo-mechanical behavior of polymeric materials is in need to quantitatively evaluate the candidate materials for high temperature applications. The Nano module of the Nanovea Mechanical Tester studies the Hardness, Young’s Modulus and Creep by applying the load with a high-precision piezo and measuring the evolution of force and displacement. An advanced oven creates a uniform temperature surrounding the indentation tip and the sample surface throughout the nanoindentation test so as to minimize the effect of thermal drift.

Teflon Mechanical Properties at High Temperature Using Nanoindentation

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Thermomechanical Analysis of Solder Using Nanoindentation

nanovea — Tue, 24 Nov 2015 15:44:44 +0000

Solder joints are subjected to thermal and/or external stress when the temperature exceeds 0.6 T_m where T_m is the melting point of the material in Kelvin. The creep behavior of solders at elevated temperatures can directly influence the reliability of solder interconnections. As a result, a reliable and quantitative thermomechanical analysis of the solder at different temperatures is in need. The Nano module of the Nanovea Mechanical Tester applies the load by a high-precision piezo and directly measures the evolution of force and displacement. The advanced heating oven provides a uniform temperature at the tip and sample surface, which ensures measuring accuracy and minimizes the influence of thermal drift.

Thermomechanical Analysis of Solder Using Nanoindentation

The post Thermomechanical Analysis of Solder Using Nanoindentation appeared first on NANOVEA: Advanced Profilometers, Tribometers, Nanoindenters, and Scratch Testers for Materials Testing.

High Temperature Scratch Hardness Using Tribometer

nanovea — Tue, 24 Nov 2015 15:34:17 +0000

Materials are selected based on the service requirements. For applications involving significant temperature changes and thermal gradients, it is critical to investigate the mechanical properties of materials at high temperatures to be fully aware of the mechanical limits. Materials, especially polymers, usually soften at high temperatures. A lot of mechanical failures are caused by creep deformation and thermal fatigue taking place only at elevated temperatures. Therefore, a reliable technique for measuring high temperature scratch hardness is in need to ensure proper selection of the materials for high temperature applications.

High Temperature Scratch Hardness Using Tribometer

The post High Temperature Scratch Hardness Using Tribometer appeared first on NANOVEA: Advanced Profilometers, Tribometers, Nanoindenters, and Scratch Testers for Materials Testing.