The cryogenic treatment of PDC cutter

PDC cutter is a composite material with excellent properties obtained by sintering diamond powder with a cemented carbide substrate using high temperature and high pressure (HTHP) technology.

The PDC cutter has great thermal conductivity, ultra-high hardness, and wear resistance, as well as high strength, high impact toughness, and easy to weld. 

The polycrystalline diamond layer is supported by the cemented carbide substrate, which can absorb the large impact loading and avoid serious damage during work. Thus, PDC was widely used for manufacturing cutting tools, geological and oil and gas well drill bits, and other wear-resistant tools. 

In the oil and gas drilling field, more than 90% of the total drilling footage is completed by PDC bits. PDC bits are normally used for soft to medium hard rock formation drilling. When it comes to deep drilling, there are still problems of short life and low ROP. 

In the deep complex formation, the working conditions of the PDC drill bit are very harsh. The main forms of failure of the composite piece include macro-fractures such as broken teeth and chipping caused by the impact caused by the drill bit receiving a large impact load, and excessive bottom hole temperature causing composite pieces. The reduced wear resistance of the sheet causes thermal wear of the PDC composite sheet. The above-mentioned failure of the PDC composite sheet will greatly affect its service life and drilling efficiency.

What’s Cryogenic Treatment?

Cryogenic treatment is an extension of conventional heat. It uses liquid nitrogen and other refrigerants as cooling media to cool materials to a temperature far below room temperature (-100~-196°C) to enhance their performance.

Many existing studies have shown that cryogenic treatment can greatly improve the mechanical properties of steel, aluminum alloys, and other materials. After cryogenic treatment, the precipitation-strengthening phenomenon occurs in these materials. The cryogenic treatment can improve the flexural strength, wear resistance, and cutting performance of cemented carbide tools, accompanied by an effective improvement of life. Relevant research has also shown that cryogenic treatment can improve the static compressive strength of diamond particles, the main reason for the increase in strength is the change of residual stress state.

But, can we improve the PDC cutter’s performance through cryogenic treatment? At this moment there are few relevant studies.

The method of cryogenic treatment

 A cryogenic treatment method for PDC cutters, the operations are:

(1) Place the PDC cutters at room temperature into a cryogenic treatment furnace;

(2) Turn on the cryogenic treatment furnace, pass in liquid nitrogen, and use temperature control to reduce the temperature in the cryogenic treatment furnace to -30℃ at a rate of -3℃/min; when the temperature reaches -30℃, it will then reduce to -1℃/min. Reduce to -120℃; after the temperature reaches -120℃, reduce the temperature to -196℃ at a speed of -0.1℃/min;

(3) Keep it for 24 hours at a temperature of -196°C;

(4) Then increase the temperature to -120°C at a rate of 0.1°C/min, then lower it to -30°C at a rate of 1°C/min, and finally reduce it to room temperature at a rate of 3°C/min;

(5) Repeat the above operation twice to complete the cryogenic treatment of the PDC cutters.

The cryogenically treated PDC cutter and untreated PDC cutter were tested for the wear ratio of the grinding wheel. The test results showed that the wear ratios were 3380000 and 4800000 respectively. The test results showed that after deep cooling The wear ratio of the cold-treated PDC cutter is lower significantly than that of the PDC cutter without cryogenic treatment.

In addition, the cryogenically treated and untreated PDC composite sheets were welded to the matrix and drilled for 200m in the same section of adjacent wells with the same drilling parameters. The mechanical drilling ROP of a drill bit is increased by 27.8% using cryogenically treated PDC compared with the one not using a cryogenically treated PDC cutter.

What do you think about the cryogenic treatment of PDC cutter? Welcome to leave us your comments.

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