| 摘要 |
According to the invention there is now provided a sintered hard material body at least partly coated with at least one 0.5-20 ) .mu.m wear resistant ceramic oxide coating being <80% thicker in the edges than on the flat surfaces. The oxide coa- ting exhibits a grain size (0) in N.m for which: .SLZERO. ~ kx + 1 where x is coating thickness in .mu.m on at least 80% of the flat surfaces of the body, k = 0.5, preferably 0.3 and 1 = 2 .mu.m for 4<x<20 and 1=0 for 0.5<x<4. The coating according to the invention is achieved by using a deposition process in which the body is in contact with a gas containing one or more halides of a metal or metals and a hy- drolysing and/or oxidizing agent forming the metal oxides and with an additional reactant (dopant) of sulphur, phosphorus, selenium, tellurium, arsenic, antimony and/or bismuth and/or compounds there-of. The temperature during deposition is in the range of 800-1000.degree.C, preferably 850-970.degree.C, and the volume con- centration of the additional reactant is 0.25-3, preferably 0.3-1 % of the total gas volume.
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