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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 steel

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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The invention claimed is: 1. In the method of depositing a MTCVD-Ti(C,N)-layer using known MTCVD-technique, the improvement comprising using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 30 to about 300 nm and having a length-to-width ratio

The invention claimed is: 1. In the method of depositing a MTCVD-Ti(C,N)-layer using known MTCVD-technique, the improvement comprising using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 30 to about 300 nm and having a length-to-width ratio (L/W) of >3. 2. The method of claim 1 wherein said improvement comprises using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 50 to about 200 nm and having a length-to-width ratio (L/W) of >5. 3. The method of claim 2 wherein said improvement comprises using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 50 to about 100 nm and having a length-to-width ratio (L/W) of >10. 4. The method of claim 1 wherein said dopant addition comprises: CO in the range from about 0.1 to about 1.0%; CO2 the range from about 0.01 to about 0.1% with a CO/CO2 ratio >8; an aluminum halide in the range from about 0.5 to about 3.0%; a zirconium halide in the range from about 0.1 to about 0.5%; and/or a hafnium halide in the range from about 0.1 to about 0.5%. 5. The method of claim 4 wherein said dopant addition comprises: CO in the range from about 0.2 to about 0.8% of the total gas flow; CO2 in the range from about 0.05 to about 0.08% with a CO/CO2 ratio >10; an aluminum halide in the range from about 1.0 to about 1.5%; a zirconium halide in the range from about 0.2 to about 0.3%; and/or a hafnium halide in the range from about 0.2 to about 0.3%. 6. The method of claim 4 wherein the zirconium halide is ZrCl4, the hafnium halide is HfCl4, the aluminum halide is AlCl3, nitrogen and carbon are supplied by CH3CN and the deposition is performed at a temperature of from about 700 to about 1000° C. 7. The method of claim 4 wherein said dopant addition comprises two or more of: CO in the range from about 0.1 to about 1.0%; CO2 in the range from about 0.01 to about 0.1% with a CO/CO2 ratio >8; an aluminum halide in the range from about 0.5 to about 3.0%; a zirconium halide in the range from about 0.1 to about 0.5%; and a hafnium halide in the range from about 0.1 to about 0.5%. 8. In the method of depositing a MTCVD-Ti(C,N)-layer using known MTCVD-technique, the improvement comprising using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 30 to about 300 nm and having a length-to-width ratio (L/W) of >3, wherein said dopant addition comprises one or more of: an aluminum halide in the range from about 1.0 to about 1.5%; a zirconium halide in the range from about 0.2 to about 0.3%; and a hafnium halide in the range from about 0.2 to about 0.3%. 9. The method of claim 8 wherein said dopant addition comprises one or more of: CO in the range from about 0.2 to about 0.8% of the total gas flow; and CO2 the range from about 0.05 to about 0.08% with a CO/CO ratio >8. 10. The method of claim 8 wherein said dopant addition comprises two or more of: an aluminum halide in the range from about 1.0 to about 1.5%; a zirconium halide in the range from about 0.2 to about 0.3%; and a hafnium halide in the range from about 0.2 to about 0.3%. 11. In the method of depositing a MTCVD-Ti(C,N)-layer using known MTCVD-technique, the improvement comprising using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 30 to about 300 nm and having a length-to-width ratio (L/W) of >3, wherein said dopant addition comprises one or more of: CO in the range from about 0.1 to about 1.0%; CO2 in the range from about 0.01 to about 0.1% with a CO/CO2 ratio >8; an aluminum halide in the range from about 0.5 to about 3.0%; a zirconium halide in the range from about 0.1 to about 0.5%; and a hafnium halide in the range from about 0.1 to about 0.5%. 12. The method of claim 11 wherein said dopant addition comprises one or more of: CO in the range from about 0.2 to about 0.8% of the total gas flow; CO2 the range from about 0.05 to about 0.08% with a CO/CO ratio >10; an aluminum halide in the range from about 1.0 to about 1.5%; a zirconium halide in the range from about 0.2 to about 0.3%; and a hafnium halide in the range from about 0.2 to about 0.3%. 13. The method of claim 11 wherein the zirconium halide is ZrCl4, the hafnium halide is HfCl4, the aluminum halide is AlCl3, nitrogen and carbon are supplied by CH3CN and the deposition is performed at a temperature of from about 700 to about 1000° C. 14. The method of claim 11 wherein said improvement comprises using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 50 to about 200 nm and having a length-to-width ratio (L/W) of >5. 15. The method of claim 14 wherein said improvement comprises using a dopant addition in order to obtain a layer composed of columnar grains with grain width of from about 50 to about 100 nm and having a length-to-width ratio (L/W) of >10. 16. The method of claim 11 wherein said dopant addition comprises one or more of: an aluminum halide in the range from about 1.0 to about 1.5%; a zirconium halide in the range from about 0.2 to about 0.3%; and a hafnium halide in the range from about 0.2 to about 0.3%. 17. The method of claim 16 wherein said dopant addition comprises one or more or: CO in the range from about 0.2 to about 0.8% of the total gas flow; and CO2 the range from about 0.05 to about 0.08% with a CO/CO2 ratio >8. 18. The method of claim 11 wherein said dopant addition comprises two or more of: CO in the range from about 0.1 to about 1.0%; CO2 in the range from about 0.01 to about 0.1% with a CO/CO2 ration >8; an aluminum halide in the range from about 0.5 to about 3.0%; a zirconium halide in the range from about 0.1 to about 0.5%; and a hafnium halide in the range from about 0.1 to about 0.5%.