US Synthetic manufactures high quality polycrystalline diamond compacts (PDCs) used in drilling for oil and natural gas. PDCs are manufactured with a sintering process that fuses premium saw-grade industrial diamond crystals under a heat of approximately 3,000 degrees Farenheit and a pressure of about 1 million psi without actually melting them. During the process, the fused diamonds are bonded to a tungsten carbide substrate. These PDC's have been around since the mid-1970s, yet manufacturers continue to experience some common problems, one being table breakage or delamination, the separation of the diamond table from the substrate.
US Synthetic's failure rates have been small and customer satisfaction is high, but some customers have reported failures on small numbers of cutters on drill bits while all of the other cutters remain intact. While this doesn't make the bit useless, it slows down the penetration and leads to an eventual loss of drilling time for costly tool withdrawal and replacement.
Resolution of this problem was turned over to the engineering team. In addition to the PDC cutter failures facing the team, the manufacturing team was looking for a way to reduce the time required to make the cutters. The reason for the cutter failures needed to be determined of frequency and manufacturing time were to be reduced.
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Comments
Problem analysis
I am sure the team has considered process steps after the diamond is bonded to the tungsten substrate. But I have this urge to jump to cause based on some previous experiences. I noticed in Fig 2 that the tungsten is silver soldered in the bit. My experience with this process is temperature control is critical in order to prevent degradation of the carbide. You also have two materials, the diamond and TC, with different coefficients of expansion. Heat up and cool down rates can cause stresses between the two materials and make them susceptible to separation under use.
Has the testing brought this into consideration? Is the silver soldering under the control of USS or the customer? In either case, what was done by USS has improved performance in the field, strict controls on the brazing process my improve even more.
Something to consider.
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