Optimizing Mechanical and Tribological Properties of Coated Automobile Components using the NanoTest System - Application Note by Micro Materials

 

Topics Covered

Background
Micro Materials NanoTest System
Using NanoTest to Optimize Properties of Coated Automobile Components
Case Study: Optimisation of DLC Coatings for Automotive Use
Customer Case Study: The University of Birmingham, UK

Background

Micro Materials Ltd are based in Wrexham, UK, which is located approximately one hour from the cities of Manchester and Liverpool.

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.

Micro Materials NanoTest System

The MML NanoTest(TM) system is a fully flexible nano-mechanical property measurement system, offering a complete range of nanomechanical and nanotribological tests, including nanoindentation, nano-scratch and wear, nano-impact and fatigue, elevated temperature nanoindentation and indentation in fluids.

Amongst other parameters, the NanoTest(TM) is capable of measuring hardness, modulus, toughness, adhesion and many other properties of thin films and other surfaces or solids.

Using NanoTest to Optimize Properties of Coated Automobile Components

Recent automotive development has concentrated on the optimisation of thin films and coatings used in a range of automotive applications, for example hard PVD coatings for coating piston rings, valve stems, bearings, gears. Also of interest is the scratch resistance of paints and clearcoats, brake pads and the fatigue wear of gears.

Many of the automobile components in question (engine components, brake pads) experience high temperatures during operation. With the NanoTest hot stage it is possible to optimize the mechanical and tribological properties of coated components at their operating temperature.

Case Study: Optimisation of DLC Coatings for Automotive Use

DLC Applications in the automotive industry include Wrist pins, Spur gears, Plungers of injector pumps, Pistons, Valve train, Camshafts, Injector needles and more.

DLC films are finding increasing use as they have many excellent mechanical properties, such as they are inert, can be used at operating temperatures up to 350¢XC, have high hardness and low friction, and experience very low levels of wear under some conditions.

However there are also some drawbacks, including the fact that DLC suffers from brittleness, high stress, poor adhesion, poor resistance to fatigue, and is often limited in its thickness due to stress build-up in thicker layers.

Nano-impact can be used to assess the toughness and bonding strength of DLC coatings under industrially relevant conditions

In the example below, the influence of applied load on time-to-fracture and failure mode was investigated for a DLC-coated engine component. At or below 5 mN cohesive fracture occurs but at higher load there is a more damaging failure mechanism. Fracture over 5 mN is accompanied by coating delamination exposing the softer substrate.

The problems highlighted in the nano-impact test are mirrored in longer engine trials. To avoid them graded DLC coatings have now been developed and the nano-impact test is an important tool in the optimisation of their properties.

No fracture at this load within 900 s

Fracture at this load within 600 s

Fracture at this load within 30 s

Tests can be repeated at loads up to 500mN with the NanoTest pendulum, or at much higher loads with the MicroTest pendulum to reproduce the contact pressure for different applications. Impact testing can be done with either loading heads up to a temperature of 500¢XC or more.

Customer Case Study: The University of Birmingham, UK

Weight saving is an important driver in high performance engines. For example, the valves in IC engines are usually made of steel. Advanced applications require lower inertial mass and light non-ferrous alloys have been suggested for engine blocks. Despite the weight saving, these materials can exhibit poor tribological properties. Researchers at Birmingham University used the NanoTest to study how the mechanical and tribological properties of FeAl and TiAl intermetallics vary with temperature, and how their load support and performance in tribo-contact can be enhanced by thermal treatment. Development of low friction and oxidation-resistant coatings for these lightweight materials is a natural progression.

Source: Micro Materials Ltd

For more information on this source please visit Micro Materials

About Micro Materials

Established in 1988, Micro Materials Ltd are manufacturers of the innovative NanoTest system, which offers unique nanomechanical test capability to materials researchers for the characterisation and optimisation of thin films, coatings and bulk materials. The current model, the NanoTest Vantage was launched on June 1st 2011.

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 25, 2008 | Updated: Apr 18, 2013
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