Turbocharger housing with a conversion coating and methods of making the conversion coating
View Patent ↗A turbocharger includes a center housing having a bearing surface configured to contact an inner surface of a unison ring. A conversion coating is impregnated onto at least the bearing surface of the center housing.
1. A turbocharger, comprising:
a center housing having a nodular iron bearing surface configured to contact an inner surface of a unison ring; and
a conversion coating including Fe 3 N impregnated onto at least the bearing surface of the center housing.
2. The turbocharger as defined in claim 1 wherein the conversion coating is a ferritic nitrocarburized coating.
3. The turbocharger as defined in claim 1 wherein the conversion coating is gas nitrocarburized coating.
4. The turbocharger as defined in claim 1 wherein the conversion coating is a plasma nitrocarburized coating.
5. The turbocharger as defined in claim 1 wherein the bearing surface is a finish machined surface.
6. The turbocharger as defined in claim 1 wherein the conversion coating further includes Fe 4 N.
7. A turbocharger center housing formed by the process of:
heating at least a nodular iron bearing surface of a center housing at a predetermined temperature;
exposing the at least the nodular iron bearing surface of the center housing to a nitrocarburizing salt bath at a temperature that is below a service temperature of the center housing, thereby impregnating a conversion coating including Fe 3 N onto at least the nodular iron bearing surface of the center housing;
exposing the at least the nodular iron bearing surface of the center housing to an oxidizing salt bath at a temperature that is below the temperature of the nitrocarburizing salt bath; and
cooling the nodular iron bearing surface.