Havar, or UNS R30004, is an

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

, possessing a very high

mechanical strength The field of strength of materials, also called mechanics of materials, typically refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. The methods employed to predict the re ...

. It can be

heat-treated Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also ...

. It is highly resistant to

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

and is

non-magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

. It is

biocompatible Biocompatibility is related to the behavior of biomaterials in various contexts. The term refers to the ability of a material to perform with an appropriate host response in a specific situation. The ambiguity of the term reflects the ongoing de ...

. It has high

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

resistance. It is a

precipitation hardening Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and so ...

superalloy A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Several key characteristics of a superalloy are excellent mechanical strength, resistance to thermal creep deformation, g ...

Chemical composition

The composition of Havar alloy is the following:

Physical properties

Havar

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

is about 1480 °C. It will retain three quarters of its room temperature strengths up to 510 °C. Its

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

is 8.3 g/cm³. Its

thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

is 13.0 W/m·K. Its

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

is 960-970 MPa and its

modulus of elasticity An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...

is 200 – 210 GPa. It can be joined by

welding Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing Fusion welding, fusion. Welding is distinct from lower ...

Gas metal arc welding Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) and metal active gas (MAG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal(s), which hea ...

( GMAW),

resistance welding Electric resistance welding (ERW) is a welding process where metal parts in contact are permanently joined by heating them with an electric current, melting the metal at the joint. Electric resistance welding is widely used, for example, in manufa ...

soldering Soldering (; ) is a process in which two or more items are joined by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involv ...

, and

brazing Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...

Applications

Havar foils of various thickness are used as diaphragms for pressure sensing in

process control An industrial process control in continuous production processes is a discipline that uses industrial control systems to achieve a production level of consistency, economy and safety which could not be achieved purely by human manual control. I ...

equipment,

medical implant An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, whi ...

s, as

particle beam A particle beam is a stream of charged or neutral particles. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and neu ...

windows for

beamline In accelerator physics, a beamline refers to the trajectory of the beam of particles, including the overall construction of the path segment (guide tubes, diagnostic devices) along a specific path of an accelerator facility. This part is either ...

s of

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle ...

s in

nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...

, and various other high-temperature applications. Havar foils are frequently used as window material for high-energy

proton beam A charged particle beam is a spatially localized group of electrically charged particles that have approximately the same position, kinetic energy (resulting in the same velocity), and direction. The kinetic energies of the particles are much lar ...

s used in the production of

fluorine-18 Fluorine-18 (18F) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96% of the time and electron capture 4% of the time ...

from

oxygen-18 Oxygen-18 (, Ω) is a natural, stable isotope of oxygen and one of the environmental isotopes. is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceu ...

enriched water. ¹⁸F is a beta plus emitter commonly used in positron emission tomography (PET) scan. The high

and the good

corrosion resistance Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

of Havar foils are both essential for the tightness and the reliability of the cyclotron targets in hospitals while also minimizing the contamination of H₂¹⁸O in the targets by the

activation product Activation products are materials made radioactive by neutron activation. Fission products and actinides produced by neutron absorption of nuclear fuel itself are normally referred to by those specific names, and ''activation product'' reserved fo ...

s of the

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...

s (Cr, Mn, Fe, Co, Ni, W, Mo) present in the

History

Havar was originally developed in the late 1940s by

Hamilton Watch Company The Hamilton Watch Company is a Swiss manufacturer of wristwatches based in Bienne, Switzerland. Founded in 1892 as an American firm, the Hamilton Watch Company ended American manufacture in 1969. Through a series of mergers and acquisitions, t ...

as an alloy for the

mainspring A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. ''Winding'' the timepiece, by turning a knob or key, stores energy in ...

s used in

watch A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by ...

es, and named Dynavar. Later it was used as sensing diaphragms and other uses, under its current name Havar.

Corrosion resistance

Its

allows use in

stress corrosion Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC ...

resistant springs and diaphragms in

oilfield A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...

equipment handling

sour crude oil Sour crude oil is crude oil containing a high amount of the impurity sulfur. It is common to find crude oil containing some impurities. When the total sulfur level in the oil is more than 0.5% (by weight), the oil is called "sour". The impurities n ...

. Havar outperforms

316L SAE 316L grade stainless steel, sometimes referred to as A4 stainless steel or marine grade stainless steel, is the second most common austenitic stainless steel after 304/A2 stainless steel. Its primary alloying constituents after iron, are c ...

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

in resistance to

pitting corrosion Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation re ...

and

crevice corrosion Crevice corrosion refers to corrosion occurring in occluded spaces such as interstices in which a stagnant solution is trapped and not renewed. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between pa ...

environment. In cold-rolled and aged form, its yield and

are higher than of other cobalt-based implant alloys. In Green death, a solution used to test the resistance to corrosion of metals, the Havar alloy does not corrode at all at

room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...

, starts corroding rapidly (15 mm/year) at 70 °C, and reaches rate of 56 mm/year at

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...

(~103 °C).

Machining

Havar is difficult to machine, as it undergoes rapid

work hardening In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context. This strengt ...

under the

cutting tool In the context of machining, a cutting tool or cutter is typically a hardened metal tool that is used to cut, shape, and remove material from a workpiece by means of machining tools as well as abrasive tools by way of shear deformation. The major ...

. The tool should be as sharp as possible and the machine should be rigid, with minimal backlash. Higher power is required than to machine ordinary steels of similar

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

References

{{Reflist Superalloys Cobalt alloys Biomaterials Chromium alloys Nickel alloys Tungsten Molybdenum alloys Ferrous alloys