Nanomechanical Testing - Variation in Material Properties with Temperature

By AZoNano Editors

Table of Contents

Introduction
NanoTest Vantage
NanoTest Vantage Hot Stage
NanoTest Vantage Cold Stage
The Nanotest High Temperature Stage
     Wear Prediction of PVD Coatings for High Speed Turning
     Creep Strain of Ti6Al4V
The Nanotest Cold Stage
     Nano-Scratch Testing of DLC Coating to –30°C
Conclusions
About Micro Materials

Introduction

Properties of materials show significant variations with changes in temperature. While characterizing or developing materials or coatings that need to be used in high temperature applications, test conditions should try and mimic those conditions that will be encountered in service conditions.

NanoTest Vantage

The NanoTest Vantage system from Micro Materials combines several nanomechanical testing techniques into a single instrument. It can also operate at temperatures up to 750°C which means that it is being used increasingly to characterize high temperature and high performance materials and components such as airframes and avionics across the aerospace industry.

NanoTest Vantage Hot Stage

The hot stage of the NanoTest Vantage allows the following operations to be performed at temperatures of around 750°C. The operations are listed below:

  • Nanoindentation
  • Nano-scratch and wear
  • Nano-impact and fatigue

NanoTest Vantage Cold Stage

The cold stage of the NanoTest Vantage allows the following operations to be conducted at temperatures down to -30°C. The operations are listed below:

  • Nanoindentation
  • Nano-scratch and wear

The Nanotest High Temperature Stage

The horizontal loading design of the NanoTest Vantage is crucial for precise and reliable testing at elevated temperatures. The configuration is shown in Figure 1.

Figure 1. Schematic of the high temperature stage of the Nanotest Vantage.

Features of the hot stage are include:

  • Horizontal loading - heat does not flow into the loading head or the depth measurement sensors positioned to the left of the probe.
  • Isothermal contact - separate heating of the sample and probe to ensure heat flow does not take place during indentation.
  • Highly localized heating ensures instrument stability
  • Time-dependent measurements – While measuring high temperatures there is no significant thermal drift and it becomes possible to perform longer duration tests such as indentation creep tests.
  • Non-ambient gases – The temperature controlled environment or purging chamber of the NanoTest Vantage provides a choice of ambient atmospheres and vastly reduces oxidation of samples.

Wear Prediction of PVD Coatings for High Speed Turning

Figure 2 shows high temperature indentation of PVD coatings and the hardness/modulus ratio that strongly influences wear in a range of tribological situations. Nanoindentation on the PVD coatings shows why TiAlN outperforms TiCN in high speed turning despite having a lower hardness value at room temperature.

Figure 2. High temperature hardness/modulus ratio for PVD TiAlN and PVD TiCN.

Creep Strain of Ti6Al4V

Figure 3 shows that the creep strain on Ti6Al4V is significantly higher at 650ºC than at 25⁰C and that in high speed cutting operations, wear resistance and lifetime of coated cutting tools are strongly correlated with their high temperature mechanical properties.

Figure 3. Creep-strain behaviour of Ti6Al4V at 25°C and 650°C.

The Nanotest Cold Stage

The NanoTest cold stage uses three stage Peltier cooling stages on both the sample and the indenter, ensuring isothermal contact during testing. An environmental enclosure is used to monitor the ambient conditions surrounding the test area.

Nano-Scratch Testing of DLC Coating to –30°C

There is a significant variation of coating characteristics with a change in temperature. The left-side figure shows a scratch track created at room temperature, showing some plastic damage but no critical failure. The figure on the right shows the same scratch carried out at -30º, displaying failure along the scratch track. Scratches run from right to left on each image.

Figure 4. Nano scratch testing of diamiond like carbon coating at room temperature (top) and at -30°C (bottom).

Conclusions

The NanoTest Vantage is capable of operations at high temperatures as well as in low temperatures and can perform operations such as nanoindentation, nano-scratch and wear. Nano-impact and fatigue is performed only at high temperatures. Wear prediction of PVD coatings as well as creep strain of Ti6Al4V can be determined using the instrument.

About Micro Materials

Established in 1988 Micro Materials has continually been at the forefront of innovation, with our pioneering approach leading to three world firsts:

  • The first commercial nanoscale impact tester, for erosive wear, toughness and contact fatigue.
  • The first commercial high temperature nanoindentation stage, capable of reaching temperatures up to 750°C.
  • The first liquid cell, allowing the testing of samples which are fully immersed in a fluid.

Micro Materials provide innovative, versatile nanomechanical test instrumentation, and respond to developments in applications in response to customer and market requirements. The integrity, reliability and accuracy of our equipment is paramount, as is our relationship with our users.

This information has been sourced, reviewed and adapted from materials provided by Micro Materials.

For more information on this source, please visit Micro Materials

Date Added: Jul 2, 2011 | Updated: Jun 11, 2013
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