Impact Performance of Polycrystalline Cutters/Drill Bits
When conducting exploratory drilling for oil, gas and other natural resources, it is often necessary to penetrate tough underground rock formations using drill bits made from ultra-hard materials. Drill bits made from industrial or natural diamonds, designed for such jobs, are manufactured under extreme temperature and pressure conditions to obtain maximum hardness and durability. Both of these features are key measures of performance in this abrasive, high-speed environment.
To remain competitive, drilling companies strive to maximize the rate at which the drill head penetrates into the rock. Prematurely worn or damaged drill bits can cause a slow down in this process. To reduce costly maintenance and improve drilling efficiency, manufacturers invest heavily in materials, equipment and in R&D labs. Impact testers are among the tools found in these labs for comparing drill bit material composition, cutting structure and manufacturing processes.
We were asked by an end user of the bits to provide a system that would allow them a way to determine which bits would work best in their end product – the drill head itself. A CEAST 9350, instrumented with a 222 kN tup, DAS (Data Acquisition System), Visual Impact software, and a custom tup insert were used to perform the testing. Due to the toughness of the specimens the tup insert was designed to allow for the insertion and removal of a carbide indenter, which had to be replaced after each impact. The drill bits were held at approximately 45 degrees in a custom fixture developed in accordance to the industry.
Each bit was impacted until it exhibited visible signs of failure – cracking, or discoloration in the face of the bit or material falling from the face. Impact energy was the controlling factor in the test methods used as the customers were interested in finding out the accumulative energy level at which the bits failed. Providing this solution has enabled the end user to determine which bits will work best in their end product.
Impact resistance is one of the most important properties for component designers to consider, as well as the most difficult to quantify. Impact resistance is a critical measure of service life and more importantly these days, it involves the perplexing problem of product safety and liability. With the combined experience of Dynatup® and CEAST, Instron® has more than 80 years experience in designing impact testing systems to simulate real-life impact conditions.
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