ICMCTF2006 Session E2: Friction and Wear of Coatings II: Design and Modeling

Monday, May 1, 2006 1:50 PM in Room California

Monday Afternoon

Time Period MoA Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2006 Schedule

Start Invited? Item
1:50 PM E2-2 Can Wear be a Friend: Wear Fatigue Interactions at the Wheel Rail Interface
A. Kapoor (University of Newcastle upon Tyne, United Kingdom)

Wear is generally considered a mode of failure and at best minimised if not avoided completely. In some situations however, especially those at the wheel rail interface the minimization of wear may lead to failure by rolling contact fatigue, a potentially catastrophic fatigue failure. Recently such a failure on the UK railway network led to many fatalities and cost the railways many billions of dollars in replacing rails which were susceptible to such failures. The subsequent research has highlighted the beneficial role played by wear in (i) producing low contact pressure by generating run-in rail and wheel profiles, and (ii) reducing the growth rate of cracks developing in the rail by crack mouth truncation. The models predict that life is governed by wear as well as rolling contact fatigue. If wear rate is reduced then the life due to wear increases, but that due to fatigue decreases, the optimum occurring at a critical wear rate. A better material with a lower wear rate performs worse in this situation!

In the past decade the rail steels have become much cleaner and the wear rate has been reduced by a factor of 10 or so. The frictional traction at curves has also been reduced by better design of railway vehicles and suspension systems. Both these effects have led to an increase in the number of Rolling Contact Fatigue incidences in the UK as well as in Europe.

The talk will review the current state of the art in this area and the work underway in the UK in understanding this phenomenon and utilising it to enhance the rail life.

2:30 PM E2-4 Rolling Contact Fatigue Behaviour of Coated Ball Bearings
J.W. Eichler, A. Leyland, A. Matthews (The University of Sheffield, United Kingdom)
The paper discusses the design and construction of an instrumented high cycle rolling contact fatigue test machine based on a thrust ball bearing test geometry. The machine is computer controlled and it monitors the speed, temperature, torque and vibration of the bearing. If any of these measurements exceed a set limit the onset of failure is detected and the machine is quick-stopped to allow detailed evalution of the failure mode. The system is currently being used primarily to evaluate the rolling contact fatigue performance of carbon-based thin films. These films can be applied to the balls and or the races of the test bearings, and the machine has demonstrated that coated races can actually worsen the bearing performance, depending on the nature of the coating, whereas coated balls can provide significant benefits. The paper will report on evaluation studies of the failed components with an aim to optimising the performance of carbon based thin films in this application.
2:50 PM E2-5 Evaluation of Coatings Used in Al Pressure Die-Casting
S. Myers (Advanced Coatings and Surface Engineering Laboratory (ACSEL)); J. Lin (Colorado School of Mines); P. Reid (Ried and Associates, LLC); B. Mishra, J.J Moore (Colorado School of Mines)
The harsh and variable environment encountered in aluminum pressure die-casting often results in premature failure, thus creating a cost factor which includes down time, loss of productivity and large quantities of scrap. A wide variety of die coatings and surface treatments are currently being used by aluminum pressure die casters in an effort to prolong die life and die casting campaigns. This paper examines the degradation mechanisms, such as washout/erosion, soldering, and thermal fatigue cracking of several common coatings and surface modifications techniques, such as ferritic nitrocarburizing and ion nitriding that have been used on core pins and inserts in both die casting trials and laboratory tests. The controlling degradation mechanisms will be proposed and promising potential die coating systems and duplex systems will be proposed.
3:10 PM E2-7 Demagnetization Map of Patterned Surface Disk Under Sliding Contact
J. Liu, D. Diao (Xian Jiaotong University, PR China)

The high storage density required in modern magnetic recording systems can be achieved by reducing the flying height of read/write head sliders over spinning disk surfaces. This can increase the likelihood of high-velocity intermittent head/disk contacts, which generates flash temperature and stress fields at the interface. The high temperature and stress fields can degrade the domain magnetization of the hard disk, which is known as the demagnetization. Former studies were not extended to give the critical conditions for the demagnetization. In this paper, therefore, our aim is to propose a demagnetization map for the identification of the demagnetization of the disk by considering the maximum temperature and stress under head/disk sliding contact. For the purpose, a coupled temperature-displacement finite element model of a patterned disk sliding contact with a slider is introduced to calculate the transient temperature and stress distributions of the magnetic media.

As the conclusions, the magnitudes of maximum temperature and stress for the magnetic media of patterned surface disk are simulated for various sliding velocities and loading conditions under sliding contact. The demagnetization map for a patterned surface disk is developed by combining the simulated results together with available demagnetization temperature/stress, the critical temperature and stress magnitude at which occurrence of demagnetization is observed experimentally. In the map, three zones, i.e. safety zone, transition zone and danger zone were divided. When the maximum stress is lower than 1.2GPa and the maximum temperature is lower than 180K, the magnetic disk is located in the safety zone without demagnetization. When the maximum stress is higher than 1.2GPa and the maximum temperature is higher than 180K, the magnetic disk is located in the danger zone. In the region between 1.2GPa and 180K, the magnetic disk is located in the transition zone.

3:30 PM E2-8 Wear and Corrosion Properties of a Low Carbon Steel Processed by Means of Surface Mechanical Attrition Treatment Followed by Lower-Temperature Chromizing Treatment
Z.B. Wang (LASMIS, University of Technology of Troyes, France)
A duplex lower-temperature chromizing treatment at 600°C for 120 min followed by 860°C for 90 min was performed on a low carbon steel plate with a nanostructured surface layer, induced by surface mechanical attrition treatment (SMAT). A chromized surface layer of about 20 abm thick was produced. Microhardness, resistances to wear and corrosion of the chromized SMAT sample were investigated, in comparison with those of the chromized coarse-grained counterpart and the as-annealed coarse-grained sample. It was demonstrated that the chromized SMAT sample showed larger hardness and superior resistances to wear and corrosion. Relative to the chromized coarse-grained counterpart, the much enhanced properties of the chromized SMAT sample might be attributed to the much thicker chromized surface layer with smaller grain size and more homogenous phase-distribution. It is anticipated that the process of the SMAT followed by a duplex chromizing treatment can be developed to significantly modify conventional chromizing technologies and to widen the application of chromizing techniques to a larger variety of materials.
Time Period MoA Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2006 Schedule