List of questions

What is the effect of coating hardness on abrasive wear resistance?

I have a few questions regarding the nature of abrasive wear. Test results, description of tested coatings and measurements can be found in the attachement.

In our test lab, we have developed a method to test the abrasive wear resistance of coatings by longitudinal turning of a material consisting of a high content of hard chromium carbide particles. When it comes to tungsten carbide, there is a clear relation between its hardness and resistance to abrasive wear, with a higher resistance for harder tungsten carbide materials.
However, when we tested PVD coatings of different hardnesses (measured at room temperature), we saw no correlation between coating hardness and the wear resistance. Instead, the tool life seemed to depend more or less on the composition of the material, the Al-content.
My question is now – what is the most probable reason for this result?
1) The main wear mechanism is not abrasive
2) The hardness is not of importance for abrasive wear resistance
3) The RT-hardness is a bad measure, since coating hardness is altered at the high temperatures
3a. And – if hot-hardness is the most important property – why do we see such a big correlation to the Al-content?
3b. Also –The RT-hardness of the Cr-particles was measured to 22 GPa, which is lower than all measures on the coatings. Can a particle of lower hardness scratch a harder material, or can we assume that the hardness of all tested coatings is decreased to a level beneath 22 GPa during the cutting process?

What materials are available that are both good electrical insulators, but also good thermal consuctors?

Det utvecklas värme i t. ex. ledare i olja i lindningsomkopplaren. Det får bli max 105°C, och man vill därför leda bort överskottsvärme så effektivt som möjligt. Ett möjligt material är BeO som har enastående värmeledningsförmåga, och samtidigt är en bra isolator, men det är dessvärre giftigt.

Are there materials with Curie-temperature around 100 degC, that could be used for heat exchange?

It can possibly be used as a cooling principle when the temperature rise in tap-changer insulation oil get "to hot".

What kind of polymer (or similar) exist that have relatively good conductor properties?

In tap-changers we sometimes use shielding rings do distribute the electric field in a good way. The metal act as perfect conductor with constant electrical potential inside its domain. At outer parts these could be of the size of 1m, meanwhile smaller shields also exist inside the tap-changer and could then be in the cm-range. The shields are normally made of aluminum due to its low weight and price. However if there exist even more lighter material with the same function this would be an interesting alternative to consider. Polymer materials (“plastics”) are easy to manufacture in complex geometries and could possibly also be used in 3D-printers.

Is it possible to improve the mechanical properties (Compressive strength, Compressive stiffness, Stress relaxation) of porous materials (fiber-based materials such as cellulose based paper/pressboard or other polymer fiber based materials such as NOMEX)?

No more than the question.

Which processes exist for producing a stiff, porous material resembling paper/pressboard?

We are interested in different kind of possible production process (electrospinning, woven fabric, wet/dry laid fibers.......)

Which methods exist for analyzing images/data obtained from in-situ X-ray synchrotron spectroscopy of compressed pressboard?

The compressive deformation on pressboard material has been depicted via X-ray syncroton images. The idea is to evaluate the change in fiber-to-fiber contact area. We now need imagining analyses for interpretation of the accumulated data.

When forming a microcellular foam structure with injection molding, mixing supercritical N2 or CO2 with the thermoplastic melt – what is the pressure inside the cavities, after molding and over time?

Will the gas be exchanged over time (e.g. CO2 out; “air” difuses in)? Can it be calculated? Can it be measured, detected?

Is it possible to use X-ray analysis to map the electronic energy band structure of the interface between SiC particles and EPDM rubber matrix in a field grading material?

A so called field grading material (FGM) is used in cable joints and cable terminations for some high voltage applications in order to decrease the electric field stress at critical places. The material is insulating at low electric fields and conducting at high electric fields. The non-linear relation between conductivity and electric field is usually explained by the particle-particle contacts of the semiconducting particles embedded in an insulating rubber. Future electric power systems are foreseen to be more complex and include higher degree of distributed power generation. This would result in more irregularities in the electric system such as for example transients and ripple.

Is it possible to use X-ray analysis to map the electronic energy band structure of the interface between the field grading material and the insulating matrix in cable joints?

A so called field grading material (FGM) is used in cable joints and cable terminations for some high voltage applications in order to decrease the electric field stress at critical places. The material is insulating at low electric fields and conducting at high electric fields. The non-linear relation between conductivity and electric field is usually explained by the particle-particle contacts of the semiconducting particles embedded in an insulating rubber. Future electric power systems are foreseen to be more complex and include higher degree of distributed power generation. This would result in more irregularities in the electric system such as for example transients and ripple.

Is there some kind of coating that could reduce the sticking of material to the pressing tools when pressing ZnO varistor blocks?

A surge arrester is used on a variety of different application within power transmission infrastructure. An example is as a protective device in front of expensive high voltage power transformers.
The “active” part of the surge arrester is a varistor that under normal operating voltage does not conduct any current. If there are sudden power surges in the transmission lines – due to switching, apparatus failures, lightning, etc. – the varistor conducts current very well and thus is able to distribute the power surge to earth in order to protect the other devices.
The varistor is made up of a sintered ceramic material, mainly comprising of ZnO. The ceramic material is mixed, spray dried and pressed to cylindrical bodies and then goes through a binder burn-out and sintering step. The spray dried material is of a certain size distribution and produced at a specific humidity range in order to reduce the internal friction of the powder during the pressing step. In order to further reduce the friction in the pressing step, a friction reducing substance is added in the powder prior to pressing. Unfortunately, this friction reducing substance is detrimental to the electrical performance if there are any residues left after sintering.
In order to keep the friction reducing material to a minimum or even to remove it completely, the friction in the material has to be reduced. As the humidity in the material is a natural friction reducer it would be beneficial to increase the humidity. However this leads to sticking of material inside the punch and die in the press. This in turn leads to build up of material on the tools which after some cycles leads to production of blocks that has to be scrapped.

Is there a method to quantify the sticking behavior of the powder in a more precise way than to press the cylindrical varistor bodies (i.e. a simplified test method)?

A surge arrester is used on a variety of different application within power transmission infrastructure. An example is as a protective device in front of expensive high voltage power transformers. The “active” part of the surge arrester is a varistor that under normal operating voltage does not conduct any current. If there are sudden power surges in the transmission lines – due to switching, apparatus failures, lightning, etc. – the varistor conducts current very well and thus is able to distribute the power surge to earth in order to protect the other devices. The varistor is made up of a sintered ceramic material, mainly comprising of ZnO. The ceramic material is mixed, spray dried and pressed to cylindrical bodies and then goes through a binder burn-out and sintering step. The spray dried material is of a certain size distribution and produced at a specific humidity range in order to reduce the internal friction of the powder during the pressing step. In order to further reduce the friction in the pressing step, a friction reducing substance is added in the powder prior to pressing. Unfortunately, this friction reducing substance is detrimental to the electrical performance if there are any residues left after sintering. In order to keep the friction reducing material to a minimum or even to remove it completely, the friction in the material has to be reduced. As the humidity in the material is a natural friction reducer it would be beneficial to increase the humidity. However this leads to sticking of material inside the punch and die in the press. This in turn leads to build up of material on the tools which after some cycles leads to production of blocks that has to be scrapped.

What are the main tribological parameters for sliding and impact abrasion mechanisms, other than initial material hardness controlling the wear behavior ?

Generally, material initial hardness is the factor to monitor in order to rank its wear resistance capability. However, this design parameter limits the material bendability and could not always guaranty the aimed wear resistance.

How can we select the wear coating under different load conditions ?

Coating can be a solution to increase the material wear resistance without affecting the bulk properties. Chosing the appropriate coating for a given working condition is important. To validate this choice, laboratory wear test methodology can be established.

Q1. For Abrasion applications (mining, drilling, etc) - how can we identify the wear mechanisms in field and select the corresponding laboratory test ?

Q2. What are the wear mechanisms involved in Concrete Mixer and Dredging applications and what are the corresponding laboratory tests?

Q3. What is the best combination of methods regarding time and cost, to cover all relevant aspects of wear (abrasive, adhesive, impact, etc.)?

BG1. Classical wear laboratory tests such as Dry Sand Rubber Wheel Abrasion Test (ASTM-G65) are simplified tests used to study the material wear behavior by generally assessing its mass loss after the wear process. These tests are generally performed to select a material for a given application. Therefore, it is important to select the best laboratory test to represent the targeted application.

BG2. Some complex applications involve combined working conditions (corrosion, wear) that is not easy to assess using simple laboratory tests. To overcome this, combined laboratory tests could be designed in order to best fit the targeted application.

BG3. Wear resistance is very complex to define. How should you test material in order to get most knowledge regarding wear resistance without using a high number of time consuming and expensive test methods?

How could the effect of test volume, test temperature and test direction be incorporated in fatigue dimensioning?

We know that parameters such as temperature, anisotropy and volume strongly affect the fatigue property of a component. However, dimensioning with respect to fatigue seems to be based on conservative values without regard to this fact. We belive there are much more opportunities with modern high quality steel. How should this be investigated and highlighted?

Q1. For Abrasion applications (mining, drilling, etc) - how can we identify the wear mechanisms in field and select the corresponding laboratory test ?

Q2. What are the wear mechanisms involved in Concrete Mixer and Dredging applications and what are the corresponding laboratory tests?

Q3. What is the best combination of methods regarding time and cost, to cover all relevant aspects of wear (abrasive, adhesive, impact, etc.)?

BG1. Classical wear laboratory tests such as Dry Sand Rubber Wheel Abrasion Test (ASTM-G65) are simplified tests used to study the material wear behavior by generally assessing its mass loss after the wear process. These tests are generally performed to select a material for a given application. Therefore, it is important to select the best laboratory test to represent the targeted application.

BG2. Some complex applications involve combined working conditions (corrosion, wear) that is not easy to assess using simple laboratory tests. To overcome this, combined laboratory tests could be designed in order to best fit the targeted application.

BG3. Wear resistance is very complex to define. How should you test material in order to get most knowledge regarding wear resistance without using a high number of time consuming and expensive test methods?

How does compressive/tensile strain in PVD coatings affect properties like electric conductivity and adhesion?

We are interested in a discussion on how compressive/tensile strain in PVD coatings will affect properties like electric conductivity and adhesion. How does crystal structure, grain size, texture and columnarity of a coating contribute to the amount of strain as well as the type of strain (compressive or tensile). Other factors might be of importance like the properties of the substrate?

In particular we would like to identify a method which can be used to measure strain in thin coatings (<100 nm) deposited on rough substrates (Ra ~ 150 nm).

How do these compare?
TEM
XRD
Nanoindentation?
Laser acoustic wave excitation?
Raman (http://onlinelibrary.wiley.com/doi/10.1002/jrs.2332/abstract) ?

What is the effect of surface topography on friction and on wear initiation?

The question relates mainly to coated metal cutting tools.

What different surface conditions impact the CVD coating on a hard metal (WC+Co) substrate? What surface parameters can be measured and what impact do they have on the coating? Are there differences between surface impacts to different coatings?

We also would like to discuss what surface parameters that can be measured and what impact they have on the coating? Are there differences between surface impacts to different coatings?

Is there a reliable method for elemental mapping on a surface (surface means 1-3 microns deep only and not more)?

We know already about EDS mapping (unable to identify light elements) and also GDOES.
The method needs to be a scan of the surface area of interest which means only several point measurements will not fulfil the task.
Application examples are to quantify surface cobalt, crushed WC or brush residues on the surface of a hard metal (WC+Co).

Is tempering on medium (0.4-0.6wt% C) carbon steels needed?

It is known that high carbon content steels (1 wt%) are brittle after martensitic hardening process and therefore tempering is applied in order to avoid to large distortion or even cracking. What tempering temperatures (if any) would be suitable for medium carbon steel grade in order to avoid the same behavior as for high carbon steel grades?

Is there a difference in stability of the retained austenite for different heating rates ranging, from slow (1 K/s) to extremely high (200 K/S), for high carbon bearing steel (1wt% C)?

When the same steel (typically 1 wt%C) is submitted to a smooth or a very quick heating rate before quenching, the resulting microstucture is martensite and retained austenite. Does the formed retained austenite have the same behaviour, in term of stability for both cases when tempering or other treatment are applied in order to reduce the retained austenite content?

How is it possible to test stress condition and material strength in complex structures of polymer material?

We have developed a fork for stables. We would like to be able to test the strength and stress condition for different polymer compositions and geometries. How do we do that?

How does effectiv deep cooling process of tool steel look like to reduce the amount of retained austenite?

Does the type of quenched martensite (lath/plate) influence the deep cooling procedure? if yes, why?
To which temperature should one deep cool the tool steel and what is the influence of the holding time?
How should the material be heated up from the deep cooling temperature to the rooms temperature?