Hardbanding of drill pipe tool joints and other drilling equipment has been around since the late 1930's. Originally, hardbanding was applied primarily to protect the drill pipe and other tools from premature abrasive wear. Since that time, there have numerous changes in hardbanding and its application, but only within the last few years has new technology been introduced that allows hardbanding to protect the casing, the marine riser and the drill pipe at the same time. Hardbanding is one of the most simple yet most misunderstood products being used on a drilling rig today. Along with the new technology being utilized to drill the highly deviated wells such as horizontal. ERD, or multi-directional, comes the problem of creating excessive downhole drag and torque. All of this drag and torque creates friction, which, in turn, creates wear on the drill string, the marine riser and the casing. Today, there are several types of wear resistant alloy hard-bandings on the market. Most of them are designed to protect either the casing, riser or the drill string, but only one or two of them can sufficiently protect all of them at the same time. Though the wear resistant alloy hardbanding technology has only been on the market for 6-8 years, it has gained increased popularity over conventional tungsten carbide hardbanding for several reasons. This technical paper will attempt to address these points in order to educate concerned parties as to which hardbanding to use in a particular situation.

The proper hardbanding with the right application can:
• Substantially increase the tool joint wear life
• Greatly reduce casing wear caused by the drill string
• Substantially reduce downhole drag and torque
• Reduce rig fuel consumption
• Allow operators to run lighter weight and grade casing.

1-Hardbanding Types

We covers two principal types of hardfacing. These comprise weld overlays that consist of wear resistant alloys that do not contain tungsten carbide granules and weld overlays consisting of tungsten carbide granules (i.e. the wear resistant phase) within a metallic substrate (normally a low carbon steel). In the text these are referred to as wear resistant alloy overlays and tungsten carbide overlays respectively.
There are a number of types of hardfacing material that can be used for the hardbanding of drill string components. The wear resistant alloy consumable used is approved . prior to commencement of the job. Alternatives may be offered for approval by Operating Company.
The Operating Company preferred hardfacings are the wear resistant alloy types and these should be used if at all possible.

A- Wear-Resistant Alloy Overlays
The wear resistant alloy overlays are recommended in place of the tungsten carbide overlays. These materials are hard alloys containing no solid abrasive particles. Therefore, unlike tungsten carbide overlays, there is no possibility of hard particles standing proud or becoming exposed from a softer matrix and producing severe abrasive wear of the casing by a machining action.

B-Tungsten Carbide Overlays
These consist of granules of tungsten carbide in a steel matrix. Either a one layer or a two layer (the abrasive layer being overlaid with a layer containing no tungsten carbide) hardfacing can be used, provided the hardfacing procedure has been fully qualified in accordance with this Specification. The hardness of the alloy steel matrix in single layer hardfacing and the first layer in the two-layer hardfacing should have a minimum Rockwell 'C' hardness of 50. Tungsten carbide particles standing proud of the substrate can cause severe casing wear by a machining action. To minimise the possibility of this happening, the carbide granules should be concentrated in the lower half of the hardfacing deposit such that they are fully embedded. Sintered and pellitised tungsten carbide with a granule size of 25 mes coarser shall be used. The nominal composition of the carbide should be 6% carbon and 6% cobalt with tungsten as the remainder.

2-Surface Preparation

A-New Components
Hardbanding shall be deposited onto a machined surface or alternatively a surface blast cleaned to white metal, (ISO 8501-1, SA2½). This surface shall be free from dirt, paint, rust and grease.
A 50-75 mm band on either side of the machined area shall also be thoroughly cleaned and degreased.
The depth of the machined surface groove for flush type hardbanding shall be determined in each instance by the Applicator to suit his welding procedure.
The following dimensions are provided for illustrative purposes only:
For flush hardbanding a 3/32 inch (2.4 mm) deep groove -0, + 1/32 inch (-0,+0.8 mm) should be machined in the surface to allow hardfacing to be applied in one layer. Alternatively for the two layer tungsten carbide hardfacing, a 1/8 inch (3.2 mm) deep groove -0, + 1/64 inch (-0,+0.4 mm) should be machined in the surface.
For proud hardbanding, in most cases, there is no requirement for a machined groove, the hardbanding is applied directly onto the prepared OD surface of the tool joint.

B-Reapplication of Hardbanding
When components are to be rehardfaced the preferred option is that new bands should not be located over the top of any existing hardbanding, especially if the existing hardbanding is tungsten carbide. The existing hardbanding shall be completely removed by gouging, grinding, or another suitable technique.
After the removal of the old hardbanding the area shall be ground to a smooth bright metal finish and the surface shall be examined by wet magnetic particle inspection (MPI) (ASME V, Article 7) to ensure the complete removal of any cracks. If the depth of the resultant groove is too great for hardbanding a buttering layer of mild steel weld metal may be deposited. At the discretion of the Applicator this layer may be subjected to machining prior to hardbanding.
For wear resistant alloy overlays where an Applicator can clearly demonstrate his ability to rehardface without removing the existing hardbanding, and fully meet the requirements of this Specification, partially worn hardbanding need not be removed prior to re-hardbanding providing the wear resistant alloy overlay to be applied is the same as the existing wear resistant alloy overlay and no cracking of the existing overlay exists.

3-Hardfacing Locations

1- Drillpipe Tool Joints
Hardbanding shall be applied to box tool joints in the following locations:
- A 3 inch (75 mm) wide band on the OD next to the taper.
- A 3/4 inch (19 mm) wide band on the 18° taper plus 3/4 inch (19 mm) long fingers projecting beyond the band at three equally spaced locations (120° apart) around the taper. The fingers may be omitted if rehardbanding also if the fingers encroach on the OD transition radius, which could cause stress raisers and initiate fatigue cracks.
FIG 1.1
For flush hardbanding, it is not possible to grind smooth the taper after hardbanding. In such cases it is only necessary to ensure that the leading edge of the hardfacing on the OD of the tool joints is smooth and rounded off.
It is recommended to hardband both box and pin tool joints, especially if the drilling conditions are onerous (rapid wear of hardbanding/tool joint envisaged) or reduced torque is required. A 2 inch (50 mm) wide weld band on the tool joint pin OD, adjacent to the 35° taper, is recommended.

2-Heavyweight Drillpipe
Hardbanding shall be applied to both the pin and box tool joints as well as the central upset wear area. The standard band widths are 4 inch (100 mm) on both the pin and box end, plus a 1 inch (25mm) wide hardband on the taper section of the box, and two 3 inch (75 mm) wide bands on the central upset area. A crack free hardbanding (preferably on that exhibits low tool joint wear in Open Hole) shall be applied proud to the central upset wear pad, recessing for the hardbanding is not permitted in light of previously documented fatigue failures at the central wear pad.
For flush hardbanding, it is not possible to grind smooth the taper after the hardbanding of new tool joints. In such cases it is only necessary to ensure that the leading edge of the hardfacing on the OD of the tool joints is smooth and rounded off.

3-Drill Collars
Hardbanding shall be applied to the following locations:
(1) Drill collars without slip and elevator recesses.
- A 10 inch (250 mm) wide band at 30 inches minimum (750 mm) from the pin shoulder.






(2) Drill collars with slip recesses.
- A 10 inch (250 mm) wide band under the slip recess and a 4 inch (100 mm) wide band above the slip recess.





(3) Drill collars with slip and elevator recesses.
- A 10 inch (250 mm) wide band under the slip recess, a 1 inch (25 mm) wide band above the slip recess, and a 4 inch (100 mm) wide band above the elevator recess.



As per below, a comparison of the wear related performance properties of the wear resistant alloys, tungsten carbide (Hughes Smooth X), and no hard facing (Bare TJ Steel).
For recommended wear resistant alloy overlays, detailed in the following subsections, are as follows:
a) ARMACOR M
b) ARNCO 100XT (superseded 200XT which exhibited excessive stress cracking)
c) ARNCO 300XT

ARMACOR M
ARMACOR M is an alloy of iron, chromium and boron; it is the generation of chromium borides, which gives the alloy its wear resistance. The as-deposited hardness of the weld deposit is in the range 52 to 54 HRC(Rockwell “C”). ATI claims that during the wear process, ARMACOR M forms a very thin, very hard amorphous (metallic glass) layer on the surface, which enhances the wear resistance, reduces the coefficient of friction, and prevents galling. DEA 42 tests have confirmed the good casing and tool joint wear resistance, and a low coefficient of friction.
ARMACOR M is available in 1/16 in. (1.6 mm) cored wire and a gas metal arc welding (GMAW) technique is generally used for its application. This type of welding equipment is widely available, meaning that the application of ARMACOR M can be performed in most parts of the world.

It is not recommended that ARMACOR M be applied over tungsten carbide or directly over itself, as detrimental cracking may occur. ATI has recently developed a Cooling, Shaping Shoe, which enables ARMACOR M to be applied over worn deposits of ARMACOR M. Another advantage of this shoe is that it assists in the rapid cooling of the weld puddle. The rapid cooling reduces the level of shrinkage and thereby reduces the residual stresses that induce cracking, increases the hardness of the weld, and provides a smoother surface finish. The results of trials have confirmed the beneficial claims for the shoe.

ARNCO 100XT
ARNCO 100XT and ARNCO 300XT are marketed by ARNCO Technology Trust, 3657 Briarpark, Houston, Texas 77042.
ARNCO 100XT is a ferrous based alloy containing chromium manganese and molybdenum, that does not exhibit cracking.
ARNCO 200XT was the predecessor of 100XT, this material was prone to stress cracking and several incidences of spalling have been experienced. The Company no longer recommends the use of ARNCO 200XT.
The welding process for 100XT is FCAW (Flux Cored Arc Welding) with a 100% CO2 shielding gas. The average as-deposited hardness of ARNCO 100XT is around 54 HRC. Good casing wear resistance, a low coefficient of friction, reasonable tool joint wear in cased hole, and good tool joint wear in open hole have been demonstrated in the DEA 42 tests. ARNCO 100XT is also available in a self-shielded, open arc version called 100XT-0A. This new version requires no shielding gas.

ARNCO 300XT
ARNCO 300XT is the latest hard facing material developed by ARNCO Technology Trust. Unlike its predecessors, ARNCO 100XT and 200XT, ARNCO 300XT is a chrome-free hard facing. The ARNCO 300XT wire cost is almost double the cost of 100XT; however, test results reflect that it lasts 5-6 times as long as 100XT. It was designed to provide improved open hole wear resistance from abrasion, which ARNCO states is significantly higher than that of the ARNCO 100XT; yet whose properties are casing wear friendly.
ARNCO 300XT alloy belongs to the family of Fe-based hard facing materials. Its typical chemical composition, in the undiluted condition, is C, Mn, Si, Ni, B, Nb. The hardness value ranges from 61-64 HRC, dependent upon the number of passes. The DEA 42 results reflected a slightly higher friction factor (0.19) than that of ARNCO 100XT. In addition, the report stated the radial wear of the ARNCO 300 XT tool joint in the open hole simulator was the lowest that Maurer Technology had ever measured for proprietary hard facing. The date of the report was 11/2/02. The diametrical wear of the ARNCO 300XT tool joint during the casing wear test was reported to be equal to that of ARNCO 100XT.