Insert chip of oil-drilling tricone bit, manufacturing method thereof and oil-drilling tricone bit

摘要

An insert chip of an oil-drilling tricone bit includes an insert-chip substrate made of a cemented carbide of a first composition, and further includes a cemented carbide coating layer constituted of at least two stacked coating layers made of a cemented carbide of a composition different from the first composition, the cemented carbide coating layer covering the whole of a cutting edge of the insert-chip substrate. The coating layers each have a thickness, at a tip portion of the cutting edge, ranging from 0.1 mm to 2.5 mm and, the total thickness of the cemented carbide coating layer ranges from 1 mm to 5 mm. The coating layers include an outermost cemented carbide layer and at least one coating layer besides the outermost cemented carbide layer and the outermost cemented carbide layer has a hardness higher than that of that at least one coating layer and of the insert-chip substrate.