Kutz M. Handbook of materials selection

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3 THE IMPACT OF ADVANCED MATERIALS ON SPORTS PERFORMANCE 1269

100

1896 1916 1936 1956 1976 1996

Date

Distance (m)

Fig. 17 Winning Olympic Games javelin throws.

ture but is sufﬁciently strong to deform the elastomer region. As a result, the

cross section will assume the cambered geometry shown. If a satisfactory shape

is achieved, the end result will be an increase in lift-to-drag ratio of the ﬁn—

one of the design parameters used to improve the ﬁn performance. The material

of choice here is carbon ﬁber/Kevlar polymer composite.

3.9 Javelin

The javelin was an event enjoyed by the Mycenaeans at least 3000 years ago.

The Greeks of 500 BC used a thin wooden javelin with a cord wrapped around

its center of mass. When thrown, the thrower held onto the end of the cord to

make the javelin rotate through the air. The rotation acted to stabilize the javelin

by averaging any non-symmetry in its construction about a central axis.

The modern javelin has relatively strict rules concerning its construction.

Essentially, the modern javelin must be smooth and has strict geometric rules to

ensure the positioning of the center of mass. The reason for this can be seen in

Fig. 17 which shows winning throws at the Olympic Games from 1904 onward.

At the Athens Olympic Games in 1908 the winning throw was just over 50 m.

In 1984, Uwe Hohn (from the then East Germany) threw a staggering 104.80

m. Given the dimensions of stadia and the fact that it was becoming unsafe for

spectators, it was decided fairly quickly by the International Amatuer Athletics

Federation that the javelin had to be redesigned to ‘‘under-perform.’’ This was

done by moving the center of mass forward by 4 cm, which caused a dramatic

loss in lift and a consequent reduction in the distance traveled.

Figure 17 shows that the distances for the new-rules javelin were approxi-

mately 15 m less after the center of mass rule change. As far as the rule makers

are concerned there are two advantages: (1) the javelin does not ﬂy as far and

(2) the javelin clearly lands tip ﬁrst. Although this reduces overall throw dis-

tances, the new rule does give the athlete one advantage. The old-rules javelin

was very sensitive to the initial throw conditions and even a small change could

reduce distances by 20 m. The new-rules javelin is much less sensitive to initial

conditions partly because it always has a negative pitching moment. This is

likely to allow the athlete to produce more consistent throws.

1270 ADVANCED MATERIALS IN SPORTS EQUIPMENT

Fig. 18 Forces acting on a skier. (From Ref. 2.)

As with the pole vault, technology strongly inﬂuences the performance of

javelin throwers, and the IAAF successfully used an equipment change to reduce

the length of throws from the mid 1980s. As Fig. 17 shows, however, it might

not be too long until a further rule change is required!

3.10 Skiing and Boards

Skis need to provide for good longitudinal torsional rigidity to allow for good

weight/pressure distribution while being ﬂexible enough to respond to different

surface properties (snow conditions) to dampen vibrations that could lead to hip

and knee injuries (Fig. 18).

Modern skis consist of a cellular core (of polymeric

or metal construction) and layered material around this core (including metals

and polymer composites reinforced with Kevlar, aramid, and carbon ﬁbers) with

metal edges of steel or high-strength aluminum alloys. Debatably, the top-of-

the-line skis, at the present time is the Volant titanium model, again with steel

edges for high hardness, toughness, and wears resistance

(Fig. 19).

3.11 Hockey Equipment

The hockey stick has changed dramatically over the years, transitioning from

wooden handles and paddles to hybrids of wood and ﬁberglass composites, and

recently to include aluminum and carbon or graphite composite shafts.

The

latter concept giving improved performance and player comfort.

4 ETHICAL CONSIDERATIONS

The use of advanced materials in sporting goods has been discussed with some

examples being given; but certainly not all that are possible. Where the sporting

achievement can be gauged in absolute terms, tremendous improvements have

been made in those sports where equipment is critical. However, use of advanced

materials in sports equipment presents us with some ethical questions.

We can

clearly enhance behavior by allowing the use of advanced materials, but where

4 ETHICAL CONSIDERATIONS 1271

Fig. 19 Volant titanium skis.

should the line be drawn? Or should there be no restrictions? The solution,

according to a young man in one of my classes at the University of Idaho, is

that if you have the patent, you (and only you) can use this material or design

no matter what it is.

This then brings us to a second question. Should we allow competition at the

highest level to be only affordable to the elite because of the high cost of equip-

ment? In turn this leads into what is perhaps the most controversial question. If

we allow certain classes of materials and designs, but not others, we can actually

favor the class of people who will excel! Let us brieﬂy examine these questions.

The carbon ﬁber vaulting pole, javelins with spiral tails, golf balls with special

dimple patterns, stiffer carbon ﬁber tennis rackets, bicycles with new types of

wheels, and the ‘‘egg position,’’ discuses with their weight distributed as close

as possible to their perimeter, and America’s Cup yachts (forget it, this one is

too complex) all lead to ‘‘further and faster.’’ We should not be Luddites but

where should this end? Can we ensure that it is people who are competing and

not the advanced materials? For sure, we do not want to force the paraplegic

athlete to go back to a wooden pylon. But how about electronically guided darts,

heat-seeking missiles for grouse shooting (allowable, provided the grouse is still

edible, according to a young lady in one of my classes at the University of

Idaho), solar-energy-enhanced bicycles, and terrain-following golf balls, which

automatically ﬁnd the lowest local elevation on a putting surface (the bottom of

the hole).

Returning to running, consider the advanced devices that allow the runner to

be catapulted forward more efﬁciently than if he were running on two human

feet (cost up to $7000). So let’s develop similar devices to be incorporated into

the shoes of Donovan Bailey (winner of the 100 m in Atlanta in a world record

9.84 s) and Michael Johnson (winner of the 200 m in Atlanta in a world record

of 19.32 s). Any bets on whether Donovan and Michael could then break 9 s

and 18 s in their respective events? Is the answer here that nothing beyond the

‘‘natural’’ springiness should be allowed?

1272 ADVANCED MATERIALS IN SPORTS EQUIPMENT

What is the answer to high costs? Many sports rules committees feel that a

reasonable compromise is to keep their sport affordable to many athletes rather

than the elite few. For example, disk wheels were initially banned from Olympic

bicycling competition because they were so expensive that they could not be

considered as available to most cyclists. Should all canoes and kayaks conform

to a single-hull design? Should the ‘‘Hoyt bow,’’ comprised of tiny glass beads

embedded in a rigid foam matrix, be allowed to compete against the traditional

wooden bow? The lack of change in behavior with temperature and minimal

moisture absorption of the new bow has led to winning scores of 1350 (out of

1440) compared to about 1100 thirty years ago—but at a price.

Let us take two examples of how legislation regarding advanced materials

can signiﬁcantly determine who wins an event. Elite rowers stand 6 ft 6 in. and

weigh about 210 lb. In contrast elite kayakers stand 6–12 in. smaller and weigh

30 lb less. This relates to allowable boat dimensions—a rowing boat can be as

long as desired, favoring strength even at higher weights (longer boats can dis-

tribute more weight over a larger area without riding too low in the water, which

leads to excessive drag). In contrast the length of a kayak is restricted, leading

to an optimized aerobic strength-to-weight ratio.

When the javelin was redesigned to be lighter and more aerodynamic, ﬁnesse

was required to make it ‘‘ﬂoat’’ correctly. Masters of this new art, such as Uwet-

lohn of East Germany (1984), deftly projected the javelin over 100 m, much to

the danger of spectators and other athletics warming up on the far side of the

stadium. The 1986 ban on the new design led to a dramatic drop in the world

record by 20 m, with the ‘‘ﬁnesse ﬂoater’’ fading to the second rank, and the

‘‘strong-arm boys’’ once again leading the way.

Lots of questions, few answers.

5 CONCLUDING REMARKS

In this chapter, I have chosen a number of sporting events to illustrate how the

magnitude of the effect of advanced materials differs depending upon the sport

in question. I then presented some ethical issues regarding the use of advanced

materials in sports, with the issues outnumbering the answers. Clearly different

sports have been affected by quite different amounts, in some cases to an extent

that has required legislation restricting certain materials and designs (titanium

baseball bats, ﬂoating javelins, nonconforming golf club drivers, etc.). However,

perhaps the best approach would be to deﬁne acceptable performance standards

rather than the conventional ad hoc regulation focused on design standards.

This should protect the essential skills of the sport, preventing it from becoming

too easy or distancing it from historic or aesthetic origins. For further details on

the use of advanced materials in sports, the interested reader is referred to two

recent conference proceedings.

21,22

Acknowledgments

The author would like to thank C. Shira, S. Haake, S. Fagg, K. A. Prisbrey, K.

Tabeshfar, and X. Velay for useful input into this chapter, and the assistance

provided by Mrs. Marlane Martonick in manuscript preparation. Acknowledg-

ment is also made to Dr. Sharon Stoll, Director of the Sports Ethics Center at

the University of Idaho (UI) and to UI students who have forced me to think

deeper about some of the ethical questions presented in this chapter.

REFERENCES 1273

REFERENCES

1. T. P. Hughes, Networks of Powder: Electriﬁcation in Western Society 1880–1930, John Hopkins

University Press, Baltimore, 1983, p. 15.

2. K. E. Easterling, Advanced Materials for Sports Equipment, Chapman and Hall, 2-6 Boundary

Row, London, 1993.

3. R. Wirhead, Athletic Ability and the Anatomy of Motion, Wolfe Medical Publication, London,

1989.

4. D. Bjerklie, ‘‘High-Tech Olympians,’’ Tech. Rev., 96, 22 (1993).

5. N. Russell, ‘‘High-Tech Sport,’’ Economist, 324, 17 (1992).

6. Atlanta ’96, The Ofﬁcial Commemorative Book of the Centennial Olympic Games, Woodford

Press, San Francisco, 1996.

7. G. Lea, ‘‘On Your Bicycle,’’ Economist, 330, 94 (1994).

8. M. F. Ashby, Met. and Mats. Trans., 26A (Dec.), 3057 (1995).

9. Anon, ‘‘High Performance Composites,’’ July / August 48 (1999), C. Grant, MRS Bull. March 50

(1998).

10. M. Fisher, Atlantic Monthly, 271(1), 78 (1995).

11. J. N. Gelberg, MRS Bull., 23(3), 39 (1998).

12. Rules of Tennis Amendment ITF upheld, July 13, 1978, President’s Newsletter, July 31, 1978.

13. C. Grant, MRS Bull. 23(3), 50 (1998).

14. A. Chou, Golf Digest, Dec., 96 (1999).

15. V. Klinkerborg, Golf Digest, Dec., 94 (2000).

16. F. H. Froes, S. Haake, S. Fagg, K. Tabeshfar, and X. Velay, Gold Digest, Dec., 32 (2000).

17. S. J. Haake, The Chronicle of the Olympics, 1896–1996.

18. H. Casey, private communication with F. H. (Sam) Froes, March 7, 2001.

19. E. M. Lenoe, MRS Bull., 23(3), 47 (1998).

20. F. H. Froes, ‘‘Is the Use of Advanced Materials in Sports Equipment Unethical?,’’ JOM, Feb.,

15 (1997).

21. A. J. Subic and S. J. Haake, (eds.), The Engineering of Sports–Research, Development and

Innovation, Blackwell Science, London, 2000.

22. Proceedings of Materials and Science in Sports Conference, San Diego, CA, F. H. (Sam) Froes

and S. J. Haake (eds.), TMS, Warrendale, PA, April 2001.

1275

CHAPTER 41

MATERIALS SELECTION FOR WEAR

RESISTANCE

Andrew W. Phelps

University of Dayton Research Institute

Dayton, Ohio

1 INTRODUCTION 1275

2 PROPERTIES OF WEAR

MATERIALS 1276

3 MATERIALS SELECTION

PROCESS 1276

4 MANUFACTURING PROCESS

SELECTION 1278

5 BASICS OF WEAR MATERIALS 1279

6 SUBSTRATE SELECTION 1280

7 SURFACE MODIFICATIONS 1280

8 FILM THICKNESS 1280

9 APPLICATIONS AND EXAMPLES

OF WEAR MATERIALS 1281

BIBLIOGRAPHY 1282

1 INTRODUCTION

The selection of materials and methods for wear applications is an important

part of both technological advancement and manufacturing activities. However,

materials selection is often viewed as a random process or worse. The individuals

charged with designing new parts, developing new processes, or overseeing com-

ponent trade study projects rarely have had the opportunity or time needed to

develop a ‘‘feel’’ for the general materials performance of metals, ceramics, or

plastics during a typical undergraduate university education. The good news is

that ignorance is curable and its treatment should leave no permanent scars.

Methods and approaches to solving materials problems have been developed

over time that may help clarify needs and reduce the degree to which materials

selection may be considered a ‘‘black art.’’ Materials application, performance,

and manufacturability are all key parts in the selection for wear resistance ap-

plications, but the general methods are also extensible to other areas of materials

selection.

There is a great deal of interest in replacing hard metallurgical coatings with

materials and systems that are more environmentally benign and are capable of

providing equal or better performance than those materials they replace. Mate-

rials replacement efforts have traditionally relied on the shotgun approach where

a material is simply substituted for another. This particular approach, however,

HandbookofMaterialsSelection.EditedbyMyerKutz

1276 MATERIALS SELECTION FOR WEAR RESISTANCE

rarely ensures success. Numerous factors must be taken into account when

choosing a replacement for a hard coating. These factors include the temperature,

work face pressure, chemical environment, materials compatibility, elastic con-

stants, and cost. If more environmentally benign materials were easily substituted

for traditional hard materials, then they would have been long ago. Because

there is no direct substitution, it is necessary to tailor the replacement materials

to the speciﬁc application.

The main tasks in materials selection for wear application are to ﬁrst specify

performance needs and then ﬁnancial needs. The order of these activities is

important because, while a lower cost component part may be preferred, that

less expensive part’s performance must be suited to the task. It is very difﬁcult

to specify a part mainly on cost without knowing the performance design limits.

This chapter is concerned mainly with the issue of performance, but one always

needs to be aware of the cost of component acquisition or manufacture.

The information base and deposition techniques developed for one class of

materials can typically be extended to other materials in the same class. Ex-

amples of this include hard coatings such as silicon carbide and titanium nitride,

soft coatings such as silver and gold, hardened metal alloys, and polycrystalline

ceramics. General wear surface selection methodology for one class of materials

may be extended to other unrelated classes.

2 PROPERTIES OF WEAR MATERIALS

A wear material may be used to reduce dimensional changes due to unwanted

material removal, reduce frictional losses, to tailor the physical performance of

a component, and/or to provide a physically stable working surface. Wear can

be divided into several categories such as adhesive and abrasive wear that take

place during sliding contact. Surface fatigue and deformation wear are an impact

or loading rate phenomenon, and corrosive wear is caused by the interaction of

the wear surface with the local environment. These wear mechanisms may act

singly or in combination with one another to alter a surface. The proper selection

of a material for a wear application will strongly depend on both the type of

wear to be countered and on the wear environment. The wear environment can

be dry, wet, warm, cold, and so on. Wear taking place in a corrosive marine

environment will be more damaging than the marine environment or the wear

alone. Wear phenomenon is a factor in applications where it might not be readily

apparent. Optical windows that are exposed to the natural elements have a need

for wear protection where dust, sand, and ice can impact and roughen soft optical

surfaces. Fan and propeller blades in water can experience wear by cavitation

erosion in water and bug and dust impact erosion in air.

3 MATERIALS SELECTION PROCESS

The classic method of selecting a wear material is to use what has always been

used in the past for a particular application. There is a reason for this—it works.

For example, steel ball bearings are relatively inexpensive and are superb at

what they do if they are not pushed beyond their performance limits. A good

reason would be needed to replace steel ball bearings in an application for an

alternative material or a different type of bearing. Changes in performance needs

such as increased rotational speeds, a need for mass or volume reduction, altered

3 MATERIALS SELECTION PROCESS 1277

mechanical shock environment, or increased reliability could lead to a demand

for an alternative material.

Few particulars are provided here in terms of speciﬁc wear materials selection.

Each wear application needs to be approached as a unique situation if a ‘‘best’’

result is to be achieved. That said, the following guidelines can allow for the

rapid selection and insertion of an optimal wear system into operational use.

1. Specify the maximum operational limits of the wear materials system for

safety and lifetime. Properties that make some wear ﬁlms excellent for one

particular application may be completely unsuitable for other uses.

2. Specify the normal operational parameters and acceptable performance

criteria of the wear materials system. Performance criteria would include the

number of cycles of use and the physical and chemical exposure environment

before, during, and after use. This step provides for the selection of a broad

range of materials and technologies that could ﬁt the needs of the application.

No preemptive elimination of technology should be attempted at this stage. Some

of the materials and technologies may later be found to be mutually exclusive

or inappropriate for use at a later point. Preemptive preselection at this point

may eliminate ‘‘poor’’ candidates but also serves to too narrowly focus the ma-

terials search too early in the process. Early candidate elimination is attractive,

but it can eliminate an entire class of potential solutions and can possibly restrict

the ultimate wear material selection to a good solution but perhaps not the best

solution. The more care that is taken during this crucial step will enable the

actual materials selection phase to be much smoother in terms of performance,

availability, and price.

3. Establish the degree of mechanical, physical (thermal expansion, dielec-

tric constant, and so on), and chemical compatibility the wear material must

have with the system. The real process of wear material selection begins once

the preceding steps have been taken.

4. Material availability and cost are closely related factors usually taken into

account at the same time. The cost of a particular wear material is almost ex-

clusively controlled by its availability. Availability is directly controlled by prev-

alence of use (numerous examples exist of high-priced ﬁnished parts made from

more common materials than their lower cost cousins) with the attendant savings

of resulting from high-volume manufacturing. Availability of raw materials and

the ability to work, shape, and form those materials can also inﬂuence materials

cost.

Cubic boron nitride is an extremely hard wear material used in tooling for

ferrous metals where diamond is inappropriate. It is a completely synthetic ma-

terial not found in nature and is produced mainly as a bulk powder in high-

pressure growth apparatus in limited batches. The powder is then used as a loose

abrasive or it can be reworked into a solid piece of tooling. For all practical

purposes, cubic boron nitride is unavailable as a directly applied coating.

The need to process the material after its synthesis adds yet another layer of

expense to the cost of tooling. Cubic boron nitride tends to be expensive due to

its availability. Titanium nitride is a fairly hard materials that is also completely

1278 MATERIALS SELECTION FOR WEAR RESISTANCE

synthetic but it is easy to produce. Inexpensive titanium-nitride-coated tooling

is now available from many suppliers.

A General Hierarchy in Cost of Manufacture of Wear Materials

Bulk materials of commonplace composition that are easy to work and form

(a) Materials that can be made in ﬁnal shape with no post processing

(b) Materials that can be made wear resistant after ﬁnal shaping as by

tempering of metal or ﬁring a ceramic

Coatings of commonplace composition that may be applied to easily manu-

factured substrates

(a) Coating applied under ambient conditions such as room temperature

and pressure

(b) Coatings formed in nontoxic water baths

trolled atmospheres

(d) Small batch vacuum-based treatments

Wear materials that are formed ex situ and then are attached to a substrate

(a) Gluing

(b) Cementing

(d) Diffusion bonding

Bulk materials of uncommon composition that are difﬁcult to work and form

such as solid carbides, borides, and silicides

4 MANUFACTURING PROCESS SELECTION

Process selection is a second-tier consideration in most instances of wear ma-

terials selection. The physical properties of wear coatings may vary depending

on the deposition method and technique. The standard cost savings from con-

tinuous and semicontinuous manufacturing methods such as extrusion and roll-

ing versus stamping and milling operations also apply for wear materials.

Method of manufacture becomes very important when directional or textural

property characteristics of a material need to be considered. Many of the phys-

ical, optical, chemical, electrical properties of wear ﬁlms will be controlled or

modiﬁed by their degree of deviation from perfection imparted during manufac-

ture. This is a common consideration in the area of composites manufacture.

The component materials of a composite structure are only slightly more im-

portant than the manner in which they are arranged in space and bound to one

another. Workpieces with apparently similar material compositions can have dra-

matically varied performance characteristics depending on the arrangement in

space of their component parts as inﬂuenced by their method of manufacture.

The physical properties of wear ﬁlms can be modiﬁed and controlled by altering

5 BASICS OF WEAR MATERIALS 1279

deposition parameters, using additives, changing substrate selection, and varying

the seeding and nucleation method.

5 BASICS OF WEAR MATERIALS

Wear materials tend to be one of two types: (1) bulk solids or (2) coatings, ﬁlms,

and surface treatments. A bulk wear material will typically provide long-term

wear surface use. There is more of a wear part available for continued use

provided that signiﬁcant dimensional changes have not affected the actual per-

formance of the tool. However, the lack of availability of a wear material in

bulk form or difﬁculty or expense in its manufacture can force the use of coatings

or ﬁlms instead. Likewise, coatings or ﬁlms can enable the use of a material

that is unsuitable in the bulk form but has very good performance when com-

bined with other materials in a multicomponent wear system. The trade-off in

the use of bulk and ﬁlm materials is the possibility of enhanced performance of

a coated tool versus the cost and effort required to make the coated tool. Other

factors such as increased tool lifetime and length of time between tool changes

may make a coated wear system attractive with respect to an inexpensive bulk

material system. Cost and availability are two factors that strongly govern the

selection of a bulk material or a surface treatment for a particular wear appli-

cation.

The following references provide a rich resource for review and further ex-

ploration of the properties and behavior of wear materials: Buckley and Rabi-

nowicz (1986), Apachitei and Duszczyk (2000), Bull and Matthews (1992), Bull

et al. (1988), Formanek et al. (1993), Jackson and Mills (2000), Joost and

Schwedes (1996), Karja et al. (1993), Foroulis (1984), Dobrzanski (2001), John

(1984).

The general application of wear materials in varied situations are addressed

in a number of the following references: Ball and Ward (1985), Balon and

Aizinbud (1989), Berns (1995), Bull et al. (2000), Burkle et al. (1995), Cooper

et al. (1992), Franklin and Beuger (1992), Franklin and Dijkman (1995), Gagg

(2001), Gandhi and Agrawal (1994), Garbar (1995), Gates and Eaton (1993),

Geiger (1992), Hsu et al. (1991), Hsu and Shen (1996), Jang and Kim (1996),

Jilbert and Field (1998), Jones (1997), Jung (2000), Klocke and Krieg (1999),

Korsunsky et al. (1995), Kuljanic (1992), Kurzynski (1996), Larsen-Basse

(1990), Lempert (1988), Llewellyn (1996), Lohmann and Van Valkenhoef

(1989), Lyons (1998), Mainwaring (1994), Manning et al. (1984), Margus and

Comerford (1994), Martinella (1993), Medley (1992), Meyerrodenbeck et al.

(1992), Mikhailin et al. (1985), Nuttall (1985), Onate et al. (1998), Paller (1991),

Pascheto and Behnood (1997), Pejryd et al. (1995), Penlington et al. (1995),

Phillips and Knapp (1995), Ramalingam and Zheng (1995), Reinhard and Volz

(1983), Robinson et al. (1993), Rozenberg et al. (1987), Sare and Arnold (1995),

Sessler et al. (1993), Sexton et al. (2001), Stack (1997), Stewart (1997), Stokes

and Cooley (1985), Suchanek et al. (1999), Thompson (1994), Uma Devi and

Mohanty (1998), Voronenko (1992), Ward et al. (1996a), Wassell et al. (1997),

and Wendl and Wupper (1991).

Hardness is related to wear in that if it is very difﬁcult to break one bond,

then the chances of breaking many bonds (wear) will be low. A related series

of references deal with the use of hard materials in wear applications: Bulloch