Boronizing Oil-well Downhole Pumps
(Rod Pumps)

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· Performance Guaranty – equal or better than big brands

· Parts and Service Guaranty – huge inventory in Texas, USA

· Price Guaranty – price match even more saving since our products has longer life than the competition to short your shutdown time

Besides our special barrels, we also has other patented products: gas anchors, sand control etc.

Hardness Compare	Silicon Sand		Boronizing		Chrome Plating	Carbon Nitriding
	Artificial	Nature	Fe2B	FeB
Vickers (HV)	1161	1364	1450	1860	900-1160	654-760
Knoop (HK)						690-788
Mohs (MM)	7	7.5
Rockwell						58-62.5
Conclusion	Sand is harder than chrome plating and other pump barrel, but Boronizing is harder than sand which can get much better pump life and cut you operation cost

Longer Life Barrels: Barrels are the most important parts in oil-well pumps, which normally account for about 60% of the total pump cost. It has been a major problem in this field to improve the service life, corrosion resistance and wear resistance of the barrels. Good news is that our company’s new invention patent (no. ZL2013.1.0166047.0), “Chemical Heat Treatment Method for Pump Barrels”, can effectively solve this problem. This method is a boronizing process for pump barrels, and has a prominent advantage in corrosion resistance and wear resistance, compared with traditional process, such as chrome plating and carbonitriding.

Boronizing with solid penetrant and well type electric furnace heating is an energy-efficient and environmentally friendly production process, without any discharge of waste water or gas. The temperature is controlled automatically by electric furnace.

Because of its excellent corrosion and wear resistance, the boronizing barrels have been well received by customers, and purchased by many oil-well pump manufacturers. Barrels and pumps of our company are also sold overseas. Barrels have been in short supply in recent years, however the production has been limited by site and some other factors. In order to make more use of this technology, provide better service to oil fields and related fields, as well as make greater contribution to the society, our company is looking for cooperators. Any party who are interested in the cooperation, please contact us for more details.

Boronizing Pump Barrels 

1. Overview of Previous Pump Barrel Processing Methods

Barrels are the most important parts of oil-well pumps, which are heavily used in oil fields. Barrels normally account for about 60% of the total pump cost^[1]. Barrels must be heat treated to improve inner hole surface hardness, wear resistance and corrosion resistance. The main heat treatment methods used in the past are the following:

1.1 Carbonitriding

Carbonitriding is a mature technology, which is widely used now. In order to increase the depth of the infiltrated layer, the barrels is usually 20steel, and heated at over 900℃. After carburizing, quenching is needed, which results in large deformation. So the next step is heavy honing. The problem of this process is that when the temperature is lower than 880℃, the content of nitrogen is ideal with a certain anti-corrosion effect, but the whole layer is thin and difficult to meet the use requirements; while when the temperature is above 900℃, the whole layer is thicker, but the content of nitrogen is little and the corrosion resistance is poor.

1.2  Hard Chrome Plating

Plating hard chromium on the inner hole surface of pump barrels can meet the requirements of corrosion resistance, wear resistance and hardness. However, chrome plating process should be reduced or avoided due to its serious environmental pollution. In addition, the inner hole surface should be alkali washed for oil removal and acid washed for activation before chrome plating. But the inner hole is too long and narrow to be washed thoroughly, which will reduce the bond strength between the coating and the substrate. During oil pumping, the inner hole surface will be peeled off due to sand abrasion and squeezing between the plunger and the barrel, which may even stuck the pump. Moreover, the chrome coating is easy to be corroded by H₂S and acid washing residue in the oil well.

1.3 Electroless plating

Electroless plating is also known as nickel-phosphorus composite plating. Its advantages and disadvantages are similar to that of chrome plating, with better corrosion resistance and acid resistance. However, the coating of electroless plating, which is only about 0.04mm, is easy to be scratched during oil pumping, and it is difficult to increase the coating thickness.

1.4 Nitriding

A qualified nitriding layer has outstanding hardness, corrosion resistance and wear resistance. The ideal nitriding material should be 38CrMoAlA, which is very expensive. The parts need to be heated in a furnace for 2 to 3 days, or even longer, which highly increases the cost. Moreover, a difficult problem is that the ammonia gas is decomposing all the time while flowing through the long and narrow hole of the barrel, so the decomposition rate of ammonia gas at the entrance side is far different from that of the exit side, and the nitride layer is very uneven. Therefore nitriding is more suitable and mature for outer surface or short holes, while it’s difficult to control the product quality for long and narrow inner holes.

1.5  Laser–quenching

This method is to apply a laser device into the barrel. When the laser device moves along the barrel axis and project laser perpendicularly onto the inner hole surface of the barrel, the barrel revolves around its axis, so the laser projection point moves helically in the inner hole surface. As the laser beams is very concentrated with an extremely high temperature, the laser projection point is heated up instantly to nearly melting point. Then after the laser projection point moves forward, the heated point is cooled down rapidly, as metal is a good conductor of heat, so that the point is quenched. It’s easy to find out that the method doesn’t change the material of the surface, so it can’t improve the corrosion resistance. In addition, the hardened zone made by laser–quenching is helical, but not the overall inner surface, so after a period of corrosion and sand wear, the unhardened zone of the inner surface will pit helically, which will increase the loss of the pump and reduce the pump efficiency.

2. Brief introduction of pump barrel boriding Technology

The technology is pump barrel boriding , with solid penetrant , without any discharge of waste water or gas, it’s environmentally friendly. The surface microstructure of the pump barrel after boronizing is FeB and Fe₂B, it‘s prominent corrosion resistance and wear resistance, especially resistance to abrasive wear is most better than other pump barrel’s surface. As far as metal boronizing is concerned, it has more than half a century's history. Everyone knows that the surface corrosion resistance and wear resistance of boriding is excellent, but it is not easy to use the technology in the pump barrel which is long and slender pipe and extremely high dimensional accuracy. Before and after 1986, many large enterprises and institutions of higher learning have cooperative research (the inventor was also involved), want to develop a boronizing pump barrel, but failed because of many difficult questions. These difficult questions as below:

1)   Firstly, boronizing at more than 900℃ can produce ideal infiltrated layer, but  pump barrel deformation is large (inner diameter tolerance>0.05mm). As pump barrels can’t be honed after boronizing, many parts are scrapped due to out of tolerance, causing the rate of finished products is very low. While boronizing at less than 880℃ can reduce the barrel deformation, but the infiltrated layer is very unsatisfactory as it’s thin and discontinuous.

2)   Secondly, if quenching is not applied after boronizing, the substrate will be too soft to bear the squeezing by sand between the pump barrel and the plunger, so the infiltrated layer will be easily chipped or peeled off; while if quenching is applied after boronizing, the barrel deformation will be too large.

After 1986, nearly 30 years, the inventor has been continuing to explore in this field , constantly adjust the agent formula and process equipment and technological method, finally achieved success, and won the national invention patentin in September 2015 , the patent number is: ZL201310166057.0.

The innovation of the invention mainly has the following five aspects:

First, the suitable penetrant formula is researched and tested, and an ideal infiltration layer can be obtained at 880.

Second, after comparing the experiment, the proper temperature control curve is determined.

Third, after test comparison, determine the appropriate infiltration pressure, and design the corresponding pressure control device. 

Fourth, the design of a dedicated well furnace and spreader, to achieve the above requirements, to ensure that after the infiltration pump barrel almost no deformation.

Fifth, the proper cooling method and device is studied，to ensure that base hardness of the pump barrel is up to standard and that it doesn't deform after cooling.

3.The Performance of Boronizing Pump Barrels

3.1 Metallographic Structure of Infiltrated Layer

The infiltration layer mainly consists of FeB andFe₂B, but single-phase Fe₂B layer is also available. Single-phaseFe₂B layer is less fragile with high hardness. The three potassium reagent (K₄Fe(CN)₆ 10g + K₄Fe(CN)₈•3H₂O1g + KOH 30g + H₂O 100g) can be applied to distinguish between these two phases: after etching with the reagent, FeB is dark brown and Fe₂Bis yellowish-brown. Figure 1 shows single-phase Fe₂B layer, with Fe₂Bwedged into the substrate. Figure 12 shows dual-phase layer, with FeB as the outer layer and Fe₂B as the inner layer. FeB is wedged into Fe₂Blayer, and Fe₂B is wedged into the substrate.

3.2  Performance of the Infiltration Layer^[3]

1)    Hardness

Microhardness of FeB is 1800~2200HV, and micro hardness of Fe₂B is 1200~1800HV. As the carbon content in steel increases, the relative content and hardness of FeB in dual-phase layer can be reduced. Refer to the following table:

2)    Wear Resistance

workpieces with FeB and Fe₂B on the surface have better wear resistance than quenched, nitride or chrome plated workpieces. Figure 3 shows the weight loss in the friction of muddy pump sleeve model and rubber plunger. The abradant is clay solution with quartz sand.

3)   Corrosion Resistance

After boronizing, the corrosion resistance of the work pieces in sulfuric acid, hydrochloric acid, phosphoric acid, various alkali and salt solutions is improved significantly, but it is not resistant to nitric acid.

4)   High Temperature Oxidation Resistance

The infiltrated layer oxidation weight increase is little when heated to 800℃ for 40 hours in the air.

5)   Red hardness

FeB and Fe₂B can maintain high hardness at 900℃^[4].

4 Surface Hardness Comparison of Common Pump Barrels

Hardness Compare	Silicon Sand		Boronizing		Chrome Plating	Carbon Nitriding
	Artificial	Nature	Fe2B	FeB
Vickers (HV)	1161	1364	1450	1860	900-1160	654-760
Knoop (HK)						690-788
Mohs (MM)	7	7.5
Rockwell						58-62.5
Conclusion	Sand is harder than chrome plating and other pump barrel, but Boronizing is harder than sand which can get much better pump life and cut you operation cost

5. Standard for Infiltrated Layer Inspection in this Invention

The infiltrated layer in this invention is originated in domestic initiative, so there is no national standard for its inspection. To control layer thickness and hardness, provide basis for manufacturing and inspection, as well as make sure the product meet the specification and customer requirements, company standard is made based on GB/T 18607-2008 standard.

The following table is the company’s inspection standard for metallographic structure, thickness and hardness of the pump barrels infiltrated layer in this invention:

Notes:

The basis and related instructions of the above companystandard are as below:

1)    Theoretical basis:

The company standard can meet the requirements of hardened layer thickness& hardness, and Base core hardness on pump barrels inner surface in Table69 of GB/T 18607-2008 standard. Take chrome plating on steel as an example, (the hardness and corrosion resistance of boronizing layer in this invention are much higher than that of carbonitriding layer, the corrosion resistance is close to that of chromium coating, and the hardness is higher than that of chromium coating),the detailed comparison is in the following table:

2)    Technical Feasibility:

        According to the pump barrel boroninzing process of our company, above requirements can be fully guaranteed. If layer thickness is to be increased, the heating temperature and the holding time must be increased accordingly, which would lead to decarburization of the substrate, and decrease the overall performance of the pump barrel.

3)    Field Test Results:

       In recent years, our company‘s boronizing pump barrels have used in many oil fields. Thousands of barrels are purchased by other oil-well pump manufacturers each year, and some of their products equipped with our barrels have been sold overseas. The feedback has always been positive. Pump barrels treated in this process and qualified by our company’s inspection standard have been proved in practice to have excellent corrosion resistance, wear resistance and other performances.

4) In order to accurately detect the hardness and thickness of the infiltrated layer, it is necessary to use the micro hardness tester. The test force is 0.1Kg or 1.0N, and the test block must be mounted before grinding and polishing.