The present invention relates to alloy compositions for protecting or re-finishing industrial tools which will be or have been exposed to wear during use. Wear arises as a result of the normal cutting or drilling or similar operations of the tool. Large industrial tools which suffer wear include drill strings used in the oil and gas industry and the present invention is concerned with providing materials to overcome or reduce such issues. However, the issue of wear at contacting surfaces in engineering applications in general is a widespread problem.

Conventionally surfaces which are prone to wear are protected by the application of hard surfacing alloys. These hard surfacing alloys are sometimes known as hard- banding alloys in the oil and gas drilling industry. Similarly, worn or part worn tools may be re-finished to extend their useful working life by the application of a hard surfacing alloy to the used tool. The hard surfacing alloys perform the function of improving the wear resistance of tools and provide a region of increased wear resistance and hardness relative to the rest of the tool. In certain cases, the hard-banding alloy is applied to a new surface to provide an initial protective layer. When the surface has been worn it can be reapplied over existing hard-banding. Normally the surfaces are inspected to ensure that any subsequent hard-banding layer is consistent with the underlying existing hard-banding layer from a metallurgical point of view. However, different layers may be the same or different composition.

A drill string is used to access underground or undersea reserves of hydrocarbon deposits in the form of oil and gas. The drill string has a drill bit at its remote end for drilling through earth and rock in the ground or seabed which is joined to a series of pipe sections which extend the length of the drill. This is done incrementally as the drill string is gradually formed from multiple sections of pipe which are screwed together as the drill bit penetrates the ground or seabed. The individual sections are usually connected together by tool joints

The drill string is rotated inside a casing which prevents collapse of the hole that is formed by the drill as it progresses. The casing is designed so that the drill bit, joints and individual pipe sections forming the drill sting as a whole can pass through the inside of the casing. As drilling progresses, some of the earth and rock which is being drilled inevitably ends up inside the drill casing and contributes to wear of the drill string as it rotates within the casing hence the casing is also prone to wear. This is of particular concern at the joints between sections of the drill string because these are of slightly larger diameter than the pipe sections forming the drill string itself. In addition, the joints may also directly contact the casing providing another source of wear at the joints. Casing is particularly prone to wear in directional wells where the well path is highly deviated.

Conventionally, this problem has been addressed by providing a surface treatment on the joints. This type of surface treatment is known as hard-facing. Hard-facing refers to the application of a wear-resistant alloy to that part of the surface of a tool which is prone to wear. The hard-facing alloy is normally applied by welding to the surface. Hard-facing alloys are usually classed as hard alloys. Carbides of metals such as tungsten and chromium are known as hard alloys and tungsten carbide has been widely used as a hard-facing material on account of its hardness. Similarly, chromium carbide has been used to impart wear resistance to surfaces.

One problem that is associated with the benefits of the hardness of tungsten carbide is that it may also cause premature wear of casing with which it is in contact.

There is therefore a need for a hard-facing alloy which is relatively economical to manufacture. It is therefore an aim of the present invention to provide hard-facing alloys which are designed so that they provide a protective function to surfaces prone to wear, such as the tool joints of drill strings. Ideally such alloys should provide wear resistance whilst at the same time not suffering the disadvantages of materials such as tungsten carbide. Ideally, the alloy is at least as hard or is harder than the rock or earth which is being drilled. Thus, an aim of the present invention is to provide a hard-facing alloy which is sufficiently hard to provide the protective function whilst at the same time not causing excessive wear in any surface that it might contact when in use (for example, the inside of a well casing). One aim is to provide a hard-facing alloy which has a relatively low coefficient of friction. Another aim of the present invention is to provide a hard-facing alloy which is strong and does not degrade the structural integrity of the substrate i.e. tool surface to which it is being applied. It is also an aim that the hard-facing alloy contributes to the structural integrity of the ensemble as a whole i.e. in the case of a drill string to the strength of the joint between successive sections of the drill string. Another aim is to provide a hard-facing alloy which has good resistance to the formation of cracks. It is also an aim that the alloy will have good longevity in use. A further aim is to provide steel alloys that have good corrosion resistance, including at elevated temperatures. A further aim is to provide a hard-facing alloy which is economical to manufacture. Another aim is to provide a hard-facing alloy which is presented in a convenient form and which is convenient to apply to a variety of industrial tools. It is also an aim of the present invention to prepare an alloy which can be produced in a process which is convenient to run so that the manufacturing process is relatively straight forward. It is also an aim to provide a process which is applicable to the large scale production of hard-banding alloy.

The present invention satisfies some or all of the above aims.

The outer surface of an industrial tool, such as a drill string joint, that will be subjected to abrasion and other wear mechanisms is protected by a hard-facing alloy of the invention. The alloys are manganese steels in general and the main additional components of the alloys of the invention are carbides of titanium, molybdenum and vanadium. It is the interplay between these three compounds in particular that give rise to the superior properties of the manganese steel alloys as hard-banding alloys when compared with conventional hard-banding alloys.

According to a first aspect of the present invention, there is provided an alloy having the following composition:

manganese in an amount of 7 to 12% by weight,

titanium in an amount of 2 to 9% by weight,

molybdenum in an amount of 0.5 to 4.0 % by weight,

calcium in an amount of 0.1 to 1.0% by weight, and

carbon in an amount of 0.25 to 2.5% by weight;

wherein the alloy optionally further comprises one or more of the following elements:

vanadium in an amount up to 4.0% by weight,

chromium in an amount of up to 2.5% by weight,

silicon in an amount of up to 1.0% by weight,

phosphorus in an amount of up to 0.05% by weight, and

sulphur in an amount of up to 0.05% by weight,

and wherein the balance is Fe and incidental impurities. These figures represent the results which can be obtained using Leco for C, S and XRF for the remainder of the elements.

This is the composition of a hardbanding alloy that has been applied to a substrate. Methods of preparing such alloys are discussed later below in more detail.

There are three important carbide forming elements in the hardbanding alloys of the present invention. These are titanium, molybdenum and vanadium. The presence of these elements in the hardbanding alloys of the invention is found to impart exceptional resistance to the formation of cracks, improved wear resistance, and improved hardness to the surface of the underlying joint or tool. The weld deposit characteristics in the hardbanding include a matrix having a fine grain size and small, evenly dispersed carbides within the matrix. A small amount of carbon is present in the matrix. Various other alloying elements may optionally be included in the hardbanding alloys to further enhance various properties exhibited by the weld deposit as described in greater detail below.

Titanium is added to the alloy because it readily forms a carbide. The titanium in the composition reacts fastest and preferentially to form titanium carbide in the presence of other elements. This material has a very high melting point, is stable at high temperature and has a low chemical reactivity. It is also extremely hard.

Molybdenum is added to the alloy because molybdenum is able to penetrate into the unit cell of titanium carbide (forming a so called solid solution) and makes the whole unit cell denser. This results in the titanium carbide being sufficiently dense that it does not float to the top of the alloy. In other words it imparts neutral buoyancy to the alloy. Molybdenum thus functions as a bimetallic carbide forming element together with titanium. Molybdenum is an element that also provides improved tensile strength of the weld and is a solid-solution strengthener.

Vanadium is added in order to produce a ternary carbide. The ternary carbide has a low coefficient of friction and this contributes to one of the beneficial properties of the hard-banding alloys of the present invention. Vanadium is a secondary carbide former and a grain refiner and also increases the toughness of the weld deposit. The carbides are preferably added to the wire as a pre alloyed mixed solid solution of FeTiMoVC in an iron matrix prepared by self propagating high temperature synthesis. This process produces a dispersion of fine carbides (5-10um) in an iron matrix. The surfaces of the carbides are thus protected from oxidation which improves wetting in the weld pool and the fine carbides are introduced as a relatively coarse powder (circa 150um) that contain the finer carbides. Additions of fine carbides directly leads to high losses due to oxidation and physical separation.

The invention therefore also relates to a process for forming a wire having a

composition as defined above (and also including the preferred arranges of

components discussed below). The process includes the step of adding carbides to the wire as a pre alloyed mixed solid solution of FeTiMoVC in an iron matrix prepared by self propagating high temperature synthesis. The steel alloys of the present invention are based on high manganese steel and as such manganese is an important component of the alloys. Manganese steels, and in particular high manganese steels, have been known for about 200 years and are known as "Hadfield steels" after their inventor. These steels provide a combination of high wear resistance with high toughness. The steels generally include a significant amount of manganese in order to obtain the wear resistance, toughness and work hardening that is required. In the case of the alloys of the present invention, we have determined that an amount of 7 to 12% by weight of manganese is necessary in order to obtain the optimum work hardening behaviour in the hardbanding alloy. More preferably the amount of manganese is in the range of 1 1 to 12% by weight since this leads to the optimum level of work hardening in the alloys of the invention.

It is important to achieve the correct balance between the amounts of titanium, molybdenum, vanadium and carbon so that an alloy of the correct hardness, coefficient of friction and density is produced. It is the interplay between these various factors that gives the alloy of the present invention it superior properties relative to conventional alloys. Furthermore, the relative amounts of titanium, molybdenum and vanadium to the manganese in these manganese steels is important.

Carbon is present mainly to form the ternary carbide. For optimum properties there must be sufficient quantity of carbon to form the mixed solid solution of TiMo(V)C . The iron matrix can also contain small amounts of carbon in solution but too high a quantity of carbon can result in reduced strength due to the formation of iron carbides.

Consequently, carbon must be present in an amount in the range of 0.25 - 2.5% by weight. In an embodiment the carbon is present in a first subrange in an amount of from 0.5 to 1.5wt%. This first subrange provides an optimum combination of wear resistance and low coefficient of friction. In another embodiment, the amount of carbon in a second subrange is from 1 to 2wt%. This second subrange provides an alloy with more wear resistance than the first subrange with a balanced low coefficient of friction.

In an embodiment, the amount of manganese is preferably 7 to 12% by weight.

Because this results in better work hardening behaviour in the hardbandings. More preferably, the amount of manganese is 1 1 to 12% by weight since this gives the best work hardening behaviour.

Titanium is added in an amount of from 2wt% to 9wt% in the alloys of the invention. Higher levels create a very viscous weld bead, lower levels can be used but wear resistance is reduced. In an embodiment the titanium is present in a first subrange in an amount of from 2 to 4.5 wt%, and more preferably the amount of titanium is from 3wt% to 4.5 wt%.This first subrange provides an optimum combination of wear resistance and low coefficient of friction. In another embodiment, the amount of titanium in a second subrange is from 4.0 to 9 wt%. This second subrange provides an alloy with more wear resistance than the first subrange with a balanced low coefficient of friction.

In an embodiment, the amount of molybdenum in the alloy is preferably up to 4.0% Molybdenum content in this range is related to the titanium content and leads to optimum buoyancy i.e. a buoyancy approaching neutral buoyancy for the mixed carbide in the weld bead. In another embodiment the molybdenum is present in a first subrange in an amount of from 0.5 to 2.5 wt%. This first subrange provides an optimum combination of wear resistance and low coefficient of friction. In another embodiment, the amount of molybdenum in a second subrange is from 2.0 to 4.0wt%. This second subrange provides an alloy with more wear resistance than the first subrange with a balanced low coefficient of friction.

The amount of vanadium in the alloy is preferably up to 2.5% by weight. In some cases, vanadium can be omitted from the alloys since the relative amounts of titanium, molybdenum and manganese provide the necessary balance of wear resistance and low coefficient of friction. When present, an amount of vanadium within the range up to 2.5wt% provides an alloy having the correct viscosity in order to be able to disperse properly around the joint and to form an effective hardbanding. If the viscosity is too low the hardbanding will spread too widely when being applied. Equally, if the viscosity is too large it becomes difficult to work and thus to form a suitable hardbanding around the joint. In an embodiment the vanadium is present in a first subrange in an amount of from 1 to 2.5wt%. This first subrange provides an optimum combination of wear resistance and low coefficient of friction. In another embodiment, the amount of vanadium in a second subrange is from 2 to 4 wt%. This second subrange provides an alloy with more wear resistance than the first subrange with a balanced low coefficient of friction.

Where first and second subranges have been defined for each of titanium,

molybdenum, vanadium and carbon, these different sub ranges apply independently to those elements. In other words, it is possible to use an amount within the first subrange in relation to say titanium and yet use an amount within the second sub range in relation to one or more of the remaining elements molybdenum, vanadium and carbon. The extent to which this is done will depend on the requirement in any particular case to optimise the combination of wear resistance and low coefficient of friction in the final alloy based on operating wholly or largely within the first subrange or the requirement of achieving an overall higher level of wear resistance based on operating wholly or largely within the second subrange.

In addition to the above components, chromium may also be independently added as an agent which improves the weldability of the hardbanding around the joint. The presence of chromium is not essential and it is simply added to improve the welding characteristics of the hardbanding. When present, chromium can be added in an amount of up to 2.5% by weight. An amount of 0.5 to 2% by weight provides a good welding finish and thus represents the optimum amount of chromium when chromium is used as an additive. As an additional benefit, chromium also provides a well- documented and effective corrosion resistance and oxidation resistance effect.

Chromium also acts as a carbide-former which ensures the formation of strengthening precipitations in the alloy. Calcium is added as an agent to improve the weldability of the hardbanding around the joint. Calcium is important because it also improves the welding finish. It can be added in an amount of up to 1 % by weight. A minimum amount of calcium of 0.1 wt% provides a good technical benefit. An amount of 0.3 to 1 % by weight provides a good welding finish and thus represents the optimum amount of calcium. In some embodiments, calcium is preferably present in an amount of from 0.3 to 0.6 wt%. In other

embodiments, a higher amount of calcium is preferred and in this case it is present in an amount of 0.6 to 1.0 wt%.

Silicon may also be independently added as an agent to improve the weldability of the hardbanding around the joint. Silicon is also not an essential component of the alloy but, when added, it also improves the welding finish. Silicon can be added in an amount of up to 1.0% by weight. The optimum amount of silicon, when present, lies in the range 0.5 to 1 % by weight since this gives the best improvement in weldability. Silicon also provides the function of a deoxidiser and is often an important component in stainless steel. Silicon may also contribute to increasing the stability of any surface oxide film. On the other hand, if the content of silicon is too high the workability of the steel is reduced.

Although chromium, calcium and silicon all independently perform the same function, in certain cases it is desirable to include two or more of those elements in combination. Thus, the inclusion of any two of those elements, or indeed all three of those elements, provides an improved weld in the hardbanding applied to a joint.

Phosphorus, when present, is generally present as a trace element in the alloy. Sulphur, when present, is generally present as a trace element in the alloy.

Aluminium, when present, is generally present as a trace element in the alloy. Although aluminium may be present in an amount of up to 1wt% or even 2wt%, depending on the source of other metals used in the alloy, it is generally preferable for the amount of aluminium to be as low as possible. Thus, ideally, the amount of aluminium is less than 0.6wt%, and more preferably less than 0.4wt% or less than 0.2wt% or less than 0.1 wt%. The aluminium does not provide any significant technical benefit in the alloys of the present invention. Furthermore, when present in a small amount it does not have any deleterious effects on the alloy. Thus it can be tolerated as an incidental impurity to levels of up to around 1wt%. Titanium that is frequently used in alloy manufacture is introduced into the alloy in the form of a titanium edition agent. Titanium addition agents generally fall into three general categories: metal scrap, ferroalloys and master alloys. The source of the titanium may therefore give rise to one or more incidental impurities which may be present in trace amounts or may be present in more substantial quantities (as is the case with the aluminium discussed above). The sources of titanium are considered separately below:

Titanium scrap may be of commercial purity (CP) titanium, or one of the many titanium- rich alloys. The most common of these is 6%AI-4%V (6-4), followed by 6%AI-2%Sn-

4%Zr-2%Mo. Scrap is generally available in the form of solid scrap, turnings or sponge.

Solid scrap is generally clean, but turnings must be degreased before use. Sponge is often from the Kroll process and may occasionally be contaminated with MgCI2.

Titanium turnings may be contaminated with lead or bismuth, which are in the brazing alloy that is often used to fix a boss onto a piece of titanium prior to machining it.

Ferrotitanium is available in many grades, but by far the most common contains approximately 70% Ti. The use of 90-6-4 scrap makes a ferroalloy with approximately 4.5% Al and 3% V, which is the basis of many specifications. CP grades of scrap can be used to make alloys with <1 % Al, but generally at a significant price premium. Tin is generally unwanted in most steels, so the tin bearing grades of scrap are used in the lower grades of ferrotitanium.

Ferrotitanium is now almost invariably made in an electric induction furnace by melting scrap titanium with iron units. Previously, the alloy was produced by aluminothermic reduction of ilmenite, using a variation of the Thermite process. This produced an alloy with about 40% Ti and 8% Al, balance Fe. This was used in the formulation of many welding rods, and such an alloy remains available today, although it is mostly used for welding and similar operations.

Since the main use of titanium is as a scavenger for carbon, nitrogen and oxygen, the steelmaker naturally prefers to buy ferrotitanium that has the lowest possible content of these elements. This is especially true as the alloy is generally priced on the titanium content, and 1 % N can combine with over 3.4% Ti. To minimize the content of carbon, oxygen and nitrogen, the titanium scrap must be carefully selected, and extra measures are taken during the ferrotitanium production process, causing a slight increase in its price.

Other impurity elements in ferrotitanium may be picked up from the titanium scrap that is used in its manufacture. These can include Cr, Ni (from stainless steel which may get mixed into the titanium scrap before it reaches the ferroalloy manufacturer), Zr and Cu.

Addition of the other essential components of the alloys to a melt may similarly give rise to the presence of incidental impurities depending on the source of the element concerned. In each case, such impurities are deemed incidental if they have no technical effect on the resulting alloy. This may be the case even if an incidental impurity is present in an amount of say 1wt% or 2wt%. The skilled person will immediately recognise which elemental components may be regarded as incidental impurities and which are essential to the working of the invention.

In circumstances in which the addition of a particular essential element in the alloy composition of the invention also results in the addition of another essential element (because the other essential element is perhaps present as an impurity in the addition agent for the first essential element) then the overall composition must be carefully monitored to ensure that all of the essential components remain within the desired parameters. If necessary, this can be compensated for by adjusting the relative proportions of additional materials used for each of the essential components in the alloys of the invention. The skilled person will be able to analyse and compensate as necessary for variations in the essential elemental components due to the presence of incidental impurities using known analytical techniques and by varying the amounts of the usual addition agents for each essential component.

The present invention relates to improved steel alloys based on high manganese steel. The experimental results presented below demonstrate that the steels of the invention have improved wear and erosion resistance relative to conventional steels.

Furthermore, the alloys of the invention can be conveniently and relatively

economically prepared. It is important to recognise, as discussed below in relation to the methods of producing the alloys, that the above composition represents the composition of the hardbanding wire. The composition of the welded deposit will be different due to factors inherent in the welding process. In particular the weld deposit will be lower in alloy levels compared to the wire due to dilution with the base materials. The degree of dilution could be reduced drastically by following a different welding technique such as Cold Metal Transfer(CMT), Laser Deposition & Plasma Transfer Arc (PTA) Welding

Technique.

Most of the conventional hardbanding materials currently used in the market are laid down by a MIG welding setup. In the MIG welding setup there is high amount of dilution in the weld. In contrast in Cold Metal Transfer (CMT), Laser deposition & Plasma Transfer Arc (PTA) welding techniques as used in the case of the materials of the invention there will be a reduced amount of dilution. This leads to improved properties in hardbanding. The alloys of the resent invention can be deposited using the above said welding techniques (CMT, Laser & PTA) and consequently exhibit improved properties relative to conventional hardbandings.

The term dilution refers to the Fe (iron) from the base material to the weld bead during welding process. As the dilution of iron increases, the composition of weld bead changes as well. A discussion concerning the influence of the welding process and parameters on dilution can be found in the following technical paper: http://www.twi- global.com/technical-knowledge/published-papers/cra-weld-ove rlay-influence-of- welding-process-and-parameters-on-dilution-and-corrosion-res istance/. Figure 7 in that paper shows the relationship between dilution and heat input for the first weld- bead for different welding processes. It can be seen for example that the the degree of iron dilution in MIG welding is 20 -40% which changes the composition of weld bead by 20-40% (since more iron goes into the weld bead, other ingredients in the weld bead decreases by 20 - 40wt%). It can also be seen from the same graph that there is a low iron dilution value of 0-20% for short circuit transfer technique (STT) and this is similar to that obtained in the Cold Metal Transfer Technique. Similar issues of dilution occur in relation to other base metals when forming welds. Thus the dilution of elements other than iron can also have a negative effect on the properties of the weld bead.

The composition quoted represents the average composition of the precursor material as a whole across the bulk material which is used to form the hardbanding layer. This point is important because the composition of the precursor wire or strip etc. that is used to form the hardbanding layer may not be uniform prior to being welded. This is because the contents of the hardbanding wire or strip are a physical mix of different elements and compounds.

According to a second aspect of the invention, there is provided a wire for use as a surface treatment, the wire having the following average composition:

manganese in an amount of 7 to 12% by weight,

titanium in an amount of 2 to 9% by weight,

molybdenum in an amount of 0.5 to 4.0% by weight,

calcium in an amount of 0.1 to 1 % by weight, and

carbon in an amount of 0.25 to 2.5% by weight;

wherein the alloy optionally further comprises one or more of the following elements:

vanadium in an amount up to 4.0% by weight,

chromium in an amount of up to 2.5% by weight

silicon in an amount of up to 1.0% by weight

phosphorus in an amount of up to 0.05% by weight

sulphur in an amount of up to 0.05% by weight, and

and wherein the balance is Fe and incidental impurities. The wire described above is a precursor to the hardbanding alloy composition which is applied to the target surface by welding.

The alloys of the invention can be used in a wide range of applications such as in drill strings, piping systems for oil transportation, chemical engineering plant applications, heavy industry and mining applications, material conveying systems, and fluids and solids transport systems where abrasive wear is a particular issue.

The hardbanding alloys of the present invention are used to produce a weld deposit. The alloys are formed into wires which are then applied to the tool or joint. The weld deposit is thus produced by melting the welding wire onto the surface to be treated. The wire may be a solid wire, a metal-cored wire or a flux-cored wire.

A metal-cored wire is in the form of a metal sheath which is then filled with a powdered metal alloy. Similarly, a flux-cored wire may is in the form of a mixture of powdered metal and fluxing ingredients. One benefit of both the metal-cored and flux-cored wires of the invention is that they allow a wide variety of alloy components and alloys to be included within the powdered metal core in addition to the alloy content provided by the sheath. This allows the overall composition of the hardbanding alloy to be fine-tuned.

Normally, for example, a hardbanding alloy precursor in the form of a wire or a strip is made from U-shaped, or similar, length of metal or alloy to which further components are added in powder form. Thus, in a first step the U-shaped length of metal has the powdered components necessary to achieve the overall alloy composition added to it, and in a further step the U-shaped tube then has its two longitudinal open edges folded together to form a tube which encapsulates the powder. This traps the powder within the void to form a powder-filled tube. The composition of the metal casing and powder thus corresponds with the composition of the ultimate hardbanding alloy and represents the composition referred to above. The precursor wire, which can be referred to as the hardbanding wire or strip, can be thought of as a blend of alloys since the metal casing may either be a single metal or an alloy and one or more of the powder components may be a single element (metallic or non-metallic) or an alloy. Conveniently, some of the alloy metals are included in the composition in the form of powdered carbides which are added to the wire.

In certain embodiments, the alloy is in the form of a tubular wire formed from a steel sheath with alloying elements contained to form the desired alloy when deposited. This is in contrast with the conventional situation of a solid wire made from the alloy. The alloy is in the form of a tubular wire formed from a steel sheath with alloying elements contained within the sheath so that an alloy of the invention having the composition described above in the various embodiments is formed in use i.e. when the tubular wire is used in a welding or hardbanding application. Thus, the melted sheath and components merge to form an alloy of the ultimate composition during use. One important feature of the present invention is that the resulting hardbanding alloys that are ultimately applied to the target substrate are produced from the blend of powdered materials in the precursor wire. Adding all of the necessary elemental components and melting them together to form a uniform composition which is then used as the welding composition is not practicable. Conversion of a cast ingot to a wire would be very difficult and expensive if not impossible as would conversion of the ingot to powder. The hard-facing material of the present disclosure may be applied onto the surface of new tools or tools having a surface comprising another worn hard-face material. The tools to which the hard-face material is applied are typically metallic in nature with steels having less than about 1 percent carbon. Examples of base metals to which the hard-face materials of the present disclosure may be applied include, but are not limited to, stainless steels, manganese steels, cast iron and iron steels, nickel-based alloys, and copper-based alloys. Examples of several hard-face materials over which the hard-face materials of the present disclosure may be applied include, but are not limited to, tungsten carbide, martensitic, and chromium carbide deposits.

According to a third aspect of the invention, there is provided a process for

hardbanding a tool joint, the process comprising welding a precursor material having the composition of the alloy or wire of any preceding claim to a target substrate. The invention thus provides a process for preparing a hardbanding at a joint. This process comprises welding a precursor material having the composition described above to a target substrate. In other words, the process involves welding wire of the second aspect of the invention to a target surface to achieve a hardbanding alloy composition on the target surface. The hardbanding alloy which results effectively has a uniform composition which is the same as the average composition in the precursor wire. It is possible to compensate for loss of certain elemental components during the welding process by varying slightly the composition of the wire. Such variation is entirely within the capabilities of the skilled person. The invention also relates to a tool which includes the hardbanding alloy of the present invention.

The wear resistant properties of the alloys of the present invention can be assessed following the Casing Wear Tests described in the American petroleum Institute (API) Standard 7CW, the first edition was published in June 2015. The content of that document and the testing procedure are not reproduced here in the interest of brevity. However, it is specifically intended that the details of that testing protocol, which are readily available to the skilled person, are specifically incorporated into the present disclosure. Thus, it is intended that this document forms part of the disclosure of the present invention in so far as it relates to the wear properties of the alloys of the present invention. This document describes a test method to create a measurable wear groove and classify the wear by determining the amount of material worn away from a casing specimen by means of abrasion. Briefly, the abrasion is created by rotating and reciprocating a drill stem element test specimen against a stationary casing specimen at a prescribed side-load. Additional abrasion is supplied by materials in the drilling fluid continuously circulated during the test procedure. The chief abrasive component within that drilling fluid is 100 mesh sand.

The lost diameter of a hardbanding alloy of the invention (designated HadTic) and of three comparative alloys was measured. The HadTic alloy of the invention had the following composition:

Carbon - 0.84 wt%

Manganese -10.67 wt%

Titanium - 3.82 wt%

Molybdenum - 2.37 wt%

Calcium 0.33 wt%

Vanadium - nil

Chromium - 2.24 wt%

Boron - nil

Silicon - 0.66 wt%

Nickel - nil

Iron - Balance

The comparative alloys had the following compositions shown in Table 1 below.

TABLE 1

3 Competitor <2% <4 <3 <4 - <20 <5 <2 - Balance

Hardbanding

III

The HadTic hardbanding alloys of the invention are strengthened by manganese and exhibits work hardening behaviour with the defined carbon and manganese ratio. Wear resistance is provided by a dispersion of fine (5um) complex carbides. The fine and dispersed complex carbides results in low coefficient of friction behaviour when the hardbanding is in contact with the casing. Wth these advantageous metallurgical benefits, HadTic hardbanding is the best wear resistance and casing-friendly

hardbanding.

From the API 7CW Procedure B results, the HadTic wear graph (Figure 1) shows evidence of work hardening behaviour with a slow wear rate and lesser wear whereas other known hardbanding alloys exhibits higher wear and wear rate. Competitor i.e.

known hardbanding alloys form mainly chromium carbides in the weld bead without any work hardening behaviour due to lesser manganese and carbon to manganese ratio. The beneficial effect of low coefficient of friction when in contact with the casing is shown in casing wear test where HadTiC shows a low wear on the casing.

Figures 1 shows the wear volume lost of hardbanding alloys and Figure 2 shows the casing wear of hardbanding alloy of the current invention (designated HadTic) and of three comparative alloys. The alloys had the compositions shown in Table 1 above. It can be seen that the alloys of the invention demonstrate both best wear resistance results and a lower casing wear compared with known hardbanding alloys.