| 摘要 |
A method of forming a coated body composed of small columnar crystals coated using the MTCVD process. Wear resistance of the prior-art Ti(C,N) layers can be considerably enhanced by optimising the grain size and microstructure. Considerably better wear resistance in, for example in many carbon steels, can be obtained by modifying the grain size and morphology of prior art MTCVD Ti(C,N) coatings. The method includes a step of doping by using CO, CO2, ZrCl4, HfCl4 and AlCl3 or combinations of these to ensure the control of the grain size and shape. Doping has to be controlled carefully in order to maintain the columnar structure and also in order to avoid nanograined structures and oxidisation. The preferred grain size should be in the sub-micron region with the grain width of from about 30 to about 300 nm. The length to width ratio should be more than 5, preferably more than 10 and the coating should exhibit a strong preferred growth orientation along 422 or 331. The XRD line broadening should be weak.
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