a silicon nitrogen layer formed on the chromium oxynitride layer the chromium oxynitride layer and silicon nitride layer protect the substrate from oxidizing at high temperatures extending the life of the coated article a method for making the coated article is also described application_number US 201113186702 A description fig1 shows a coated article 10 according to an exemplary embodiment the coated article 10 includes a substrate 11 a base layer 13 formed on the substrate 11 a chromium oxynitride cron layer 15 formed on the base layer 13 and a silicon nitride sin layer 17 formed on the cron layer 15 the substrate 11 may be made of stainless steel or die steel the base layer 13 is a layer of chromium an vacuum sputtering process may form the base layer 13 the base layer 13 has a thickness of approximately 0 1 micrometers 0 1 u03bcm to 0 2 u03bcm an vacuum sputtering process may be used to form the cron layer 15 the cron layer 15 has a thickness of about 0 5 u03bcm to 1 5 u03bcm the cron layer 15 is composed of small nanocrystals with a very small gap between the crystals thus the cr u2014 o u2014 n layer 15 is dense enough to delay the penetration of outside oxygen through to the substrate 11 an vacuum sputtering process may be used to form the si u2014 n 17 the silicon nitride layer 17 has high hardness and good wear resistance thus effectively protecting the cr u2014 o u2014 n layer 15 the silicon nitride layer 17 has a thickness of.