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Chapter 1

Cryogenic Processing: State of the Art, Advantages and Applications Susheel Kalia and Shao-Yun Fu

Contents 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 A Brief History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Cryogenic Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 The Science of Cryogenic Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Polymers at Cryogenic Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Advantages of Cryogenic Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Applications of Cryogenic Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Conclusions and Future Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract Cryogenic processing is the one-time permanent treatment of the materials at very low temperatures to increase the physical and mechanical properties. Cryogenic processing is capable of treating a wide variety of materials such as metals, alloys, polymers, carbides, ceramics and composites. Cryogenic applications of polymers are not only limited to the fields of space, electrical and superconducting technology but also to other advanced technologies such as cryosurgery and cryobiology in the medical field. Keywords Cryogenic processing • Materials • Polymers • Mechanical properties

S. Kalia (*) Department of Chemistry, Bahra University, Waknaghat 173 234, Dist. Solan (H.P.), India e-mail: susheel.kalia@gmail.com S.-Y. Fu Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China e-mail: syfu@mail.ipc.ac.cn S. Kalia and S.-Y. Fu (eds.), Polymers at Cryogenic Temperatures, DOI 10.1007/978-3-642-35335-2_1, # Springer-Verlag Berlin Heidelberg 2013

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1.1

S. Kalia and S.-Y. Fu

Introduction

Cryogenic processing is the process of deep-freezing materials at cryogenic temperatures to enhance the mechanical and physical properties of materials being treated. It is a supplementary process to conventional heat treatment process. The cryogenic processing on materials increases wear resistance, hardness, and dimensional stability and reduces tool consumption and downtime for the machine tool set-up, thus leading to cost reductions [1]. The technique of cryogenic processing is an inexpensive method that improves the physical and mechanical properties of materials such as metals, plastics and composites. The word “cryogenic” comes from the Greek word “kryos”, which means cold and is simply study of materials at low temperature such as 77 K. Cryo processing refines and stabilizes the crystal lattice structure and distributes carbon particles throughout the material resulting in a stronger and hence more durable material [2].

1.2

A Brief History

Scientists have been experimenting with the use of extreme cold to strengthen metals since the mid-1800s, but it was not until the advent of space travel that cryogenic processing really came into own. NASA engineers analyzed spacecraft that had returned from the cold vacuum of space and discovered that many of metal parts came back stronger than they were before spending time in space. Cryogenics and refrigeration technologies share a common history. The most obvious difference between two is the temperature range. Cryogenics had its beginning in the mid of nineteenth century when for the first time man learned to cool objects to a temperature lower than had ever existed naturally on the surface of earth. First practical vapour compression refrigerator was invented by James Harrison in 1855. In 1872, Sir James Dewar invented the vacuum flask. The air first liquefied in 1883 by Polish scientist named Olszewski. Ten years later Olszewski and a British scientist Sir James Dewar liquefied hydrogen. In 1902, Georges Claude improved the efficiency of air liquefaction by including reciprocating expansion engine. The Dutch Physicist Kamerlingh Onnes finally liquefied helium in 1908. Thus, by the beginning of twentieth century, the door had been opened to a strange new world of experimentation [3–7]. Cold treatments were reported to have beneficial effects on tool performance as far back as 1937. Both in the United States and Europe, several reports have appeared of substantial benefits which can be realized by treating steel tools at a low temperature, around 77 K. Within the United States, claims for improvements have been expanded to include copper (Cu), carbides, nylon and some high temperature alloys [3]. The method of cryogenic processing materials at sub-zero temperatures was first acknowledged when metal parts that were transported via train had been crammed with dry ice (at 79 C), resulting in perceptible increases in wear resistance [8]. Work is being done to confirm that cooling below the temperature of dry ice

1 Cryogenic Processing: State of the Art, Advantages and Applications

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( 79 C), at boiling temperature of liquid nitrogen ( 196 C), would further improve the physical properties of materials [9].

1.3

Cryogenic Processing

Cryogenic processing is capable of treating a wide variety of materials such as metals, alloys, polymers, carbides, ceramics and composites. Deep cryogenics is the ultra low temperature processing of materials to enhance their desired metallurgical and structural properties. This is a temperature about 77 K. Cryogenic processing uses temperature around 77 K because this temperature is easily achieved using computer controls, a well-insulated treatment chamber and liquid nitrogen as shown in Fig. 1.1. Cryogenics is a dry process in which liquid nitrogen is converted to a gas before it enters the chamber so that it does not come into contact with the parts assuring that the dangers of cracking from too fast cooling are eliminated. The risk of thermal shock is eliminated as there is no exposure to cryogenic liquids. The whole process takes between 36 and 74 h depending upon the type and weight of material under treatment. Cryogenic processing must be done correctly in order for it to be successful. The basic steps in a cryogenic process are as follows [2, 10, 11]: • Ramp down: cryogenics involves slow cooling of the material from room temperature to 77 K and ramp down time is in the 4–10 h range. • Hold: the material is soaked or held at 77 K for 20–30 h which depends upon the volume of the part. This is the part of the treatment in which the micro-structural changes are realized. • Ramp up: finally the material is brought back to room temperature. The ramp up time can be from 10 to 20 h range.

1.4

The Science of Cryogenic Processing

Cryogenics refines and stabilizes the crystal lattice structure and distributes carbon particles throughout the material resulting in a stronger and hence more durable material. All of the individual particles that make up an alloy are placed into their most stable state. These particles then are aligned optimally with surrounding particles. Also, molecular bonds are strengthened by the process [2]. Particle alignment and grain refinement combine to relieve internal stresses, which can contribute to part failure. This results in material that is optimized for durability. The extremely low temperature during cryogenic processing also slows the movement at atomic levels and increases the internal molecular bonding energy and hence promotes a pure structural balance throughout the material (Fig. 1.2) [2, 12]. As a result of cryogenic processing, material is obtained with an extremely uniform, refined and dense microstructure which ultimately leads to improvement in physical and mechanical properties.

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a

b

500

Temperature (K)

450K 400

300

200

100

77K 0

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10

15

20

25

30

Time (h) Fig. 1.1 (a) Set-up of cryogenic processing in the temperature of 77–450 K, which consists of a well-insulated treatment chamber (left), a liquid nitrogen dewar (right), cryogenic media transport tube, temperature controlling and data acquisition system; (b) temperature (77–450 K)-time curve with controllable heating and cooling speed

Fig. 1.2 Increase in bonding energy at atomic levels with decrease in temperature [2]

1.5

Polymers at Cryogenic Temperature

Applications of plastics in several areas are of special interest because of their excellent electrical, thermal and mechanical properties. The research work in the field of cryogenic treatment of polymers has gained significant attention in recent years. Cryogenic treatment is found to be the most effective tool to improve wear


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resistance capacity of polymers. In cryogenic treatment of polymers, the polymer materials are subjected to sub-zero temperature for a stipulated time using liquid nitrogen or liquid helium etc. Since during the cryogenic treatment the whole bulk is also affected, so it is not merely the surface phenomenon. During cryogenic processing, the extremely low temperature during cryogenic processing also slows the movement at atomic levels and increases the internal molecular bonding energy and hence promotes a pure structural balance throughout the material. Cryogenics technology has proven to be the best in case of metals but the need for the development of hypersonic vehicles and cryogenic storage tanks etc. has led to the evaluation of lightweight materials like polymers [2, 13]. Michael et al. [14] have carried out the tensile tests on various epoxies at room temperature and 77 K and observed that these materials are relatively brittle and show plastic behaviour at room temperature just before fracture. Whereas at 77 K no plasticity was observed, the modulus of elasticity was increased by a factor of 3. Stress–strain behaviour and fracture behaviour of polyimide were measured at 77 and 4.2 K. The modulus of elasticity and ultimate tensile strength were increased by 40 % and 60 %, respectively by cooling up to 77 K, but no further change was observed up to 4.2 K [15]. Effect of cryogenic treatment on tensile strength, elongation at break and modulus of elasticity of some polymers are listed in Table 1.1 [16].

1.6

Advantages of Cryogenic Processing

Cryogenically treated parts not only improve performance but also increase the life of materials. Main advantages include [17]: • One of the most important advantages for cryogenic treatment of materials is an increase in wear resistance. • The structure of materials is permanently changed, resulting in improved mechanical properties. Treated components may be ground after treatment and the benefits of treatment are retained. • The frequency and cost of tool remanufacture are reduced. Treated worn tools require less material removal to restore a uniform cutting edge. • Machine downtime caused by tool replacement is substantially reduced. • Surface finishing is improved on material being manufactured with treated tooling. Treated tooling stays sharper and in tolerance longer than untreated. • The overall durability of the treated material is increased. • Refinishing or regrinds do not affect permanent improvements. • Thermal shock is eliminated through a dry, computer controlled process. • Brittleness is decreased. • Tensile strength, toughness and stability are improved. • Internal stresses are relaxed. • The orderly arrangement of crystals is caused, internal bonding energy is increased, and a structural balance throughout the mass of the material is achieved.

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Table 1.1 Tensile strength of various plastics at different temperatures [16]

Materials Plastic films & paper Polyimide (H film)

Polycarbonate (Makrolon)

Polyamide (Nomex)

Polyethylene terephthalate (Mylar) Polyvinylchloride (rigid type)

Polyethylene (high density)

Polytetrafluoroethylene (Teflon)

Temperature (K)

Tensile strength (MPa)

Modulus of Elongation at elasticity break (%) (MPa)

298 77 4.2 298 77 4.2 298 77 4.2 298 77 4.2 298 77 4.2 298 77 4.2 298 77 4.2

18.2 32.5 34.0 6.4 13.5 15.6 8.3 14.5 15.8 16.5 26.0 26.8 2.3 9.5 11.6 2.5 10.5 13.5 2.0 4.3 5.6

44 16 8 112 4.5 3.0 21 3.5 3.0 88 9.5 5.5 156 3.6 2.9 525 4.3 3.1 480 6.5 3.5

Bulk materials Polyimide (Vespel) 77 18.4 Polyethylene (high density) 77 13.8 Polyvinylchloride (rigid) 77 11.5 Copyright 1976, reproduced with permission from Elsevier

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510 640 615

450 870 880 110 215 300

145 217

3.1 2.3 11.5

Applications of Cryogenic Processing

There are several categories of industrial applications and representative parts [12]: • Paper and corrugated board industry: chipper knives, slitter knives, tape cutters, paper drills, trimmers, tissue perforators. • Cutting tools: mill, cutters, ball screws, punches, drills, broaches. • Performance vehicles: crankshafts, brake rotors, push rods, heads, pistons, blocks, cams. • Plastics industry: trimmers, mill knives, granulating blades, dies, feed screws. • Other applications: copper, electrode, gun barrels, sporting goods, razor blades, musical instruments.


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Conclusions and Future Prospects

Cryogenic processing is an inexpensive one-time permanent treatment of the materials at very low temperature such as 77 K. This technique improves the physical and mechanical properties of the materials. Cryogenic applications of polymers are not only limited to the fields of space, electrical and superconducting technology but also to other advanced technologies such as cryosurgery and cryobiology in the medical field. More applications of cryogenic processing will take off in the near future. Applications of polymeric materials at cryogenic temperatures usually require a lot of attentions because of severe cryogenic conditions; there is limited work yet and a lot of work has to be done on the cryogenic treatment of polymers. Further newer materials have to be developed with capacity of bearing severe cryogenic conditions.

References 1. Gill SS, Singh H, Singh R, Singh J (2010) Cryoprocessing of cutting tool materials—a review. Int J Adv Manuf Tech 48:175–192 2. Kalia S (2010) Cryogenic processing: a study of materials at low temperatures. J Low Temp Phys 158:934–945 3. Foerg W (2002) History of cryogenics: the epoch of the pioneers from the beginning to the year 1911. Int J Refrig 25:283–292 4. Scurlock RG (1990) A matter of degrees: a brief history of cryogenics. Cryogenics 30:483–500 5. Steckelmacher W (1993) History and origin of cryogenics. In: Scurlock RG (ed) Monographs on cryogenics, vol 8. Oxford University Press, Oxford, p 653 6. Richardson RN, Stone HBJ (2003) The cooling potential of cryogens. Part 1 – the early development of refrigeration and cryogenic cooling technology. Ecolibrium (Australian Institute of Refrigeration Air Conditioning and Heating), pp. 10–14 7. Timmerhaus KD (1982) The cryogenic engineering conference—a record of twenty five years of low temperature progress. Advances in Cryogenic Engineering, vol 27. Plenum, New York, p 1 8. Brown J (1995) Big chill to extend gear life. Power Transm Des, pp. 59–61 9. Sweeney TP Jr (1986) Deep cryogenics: the great cold debate. Heat Treat 18:28–32 10. Singh PJ, Guha B, Achar DRG (2003) Fatigue life improvement of AISI 304 L cruciform welded joints by cryogenic treatments. Eng Fail Anal 10:1–12 11. Gulyaev A (1937) Improved heat treatment of high speed steel. Metallurgy 12:65–70 12. Singh R, Gupta S (2006) National seminar on nonferrous metals—imperative need for sustainable development. Indian Institute of Metals, Khetari Nagar Chapter, Rajasthan, India, pp 45–48 13. Pande KN, Peshwe DR, Kumar A (2012) Effect of the cryogenic treatment on polyamide and optimization of its parameters for the enhancement of wear performance. Trans Indian Inst Met 65:313–319 14. Michael PC, Aized D, Rabinowicz E, Iwasa Y (1990) Mechanical properties and static friction behaviour of epoxy mixes at room temperature and at 77 K. Cryogenics 30(9):775–786 15. Tschegg E, Humer K, Weber HW (1991) Mechanical properties and fracture behaviour of polyimide (SINTIMID) at cryogenic temperatures. Cryogenics 31:878–883 16. van de Voorde M (1976) Results of physical tests on polymers at cryogenic temperatures. Cryogenics 16:296–302 17. http://www.cryoplus.com/advantages.php