| 摘要 |
<p>PURPOSE:To prolong the life of a spade drill blade by coating its margin, chisel- edge and thinning parts with a single or multiple hard coating layer. CONSTITUTION:The above-mentioned parts of a spade drill blade made of tungsten-carbide radical hard metal are coated, by an ordinary method, with a coating layer 0.5-20mum thick composed of a single layer of one kind or a multiple layer of two or more kinds of substances selected from groups consisting of carbide, nitride, carbide-nitride, carbonate and carbonate-nitride of the metals belonging to 4a, 5a and 6a families in the periodic table, as well as aluminum oxide and further solid solution of two kinds or more of these metals.</p> |
