A method for processing at least one article in an arrangement comprising a pressure vessel, a furnace chamber provided inside the pressure vessel, and a load compartment arranged inside the furnace chamber, wherein the method comprises: performing hot isostatic pressing by the following steps: providing at least one article to be processed inside the load compartment; feeding, via a pressure medium feeding device, a pressure medium into the pressure vessel and increasing the pressure in the load compartment; increasing the temperature in the load compartment; maintaining the increased temperature at a first predetermined temperature level (T 1) for a selected period of time (t 1); maintaining the increased pressure at a first predetermined pressure level (Pi) for a selected period of time (t 2); and thereafter, performing case hardening by the following steps: changing the temperature from the first predetermined temperature level to a second predetermined temperature level (T 2); feeding, via a gas feeding device separate from the pressure medium feeding device, a carbon-containing gas into the pressure vessel; maintaining the second predetermined temperature level for a selected period of time (t 3); reducing the temperature in the load compartment; and discharging the pressure medium from the pressure vessel and reducing the pressure in the load compartment. performing hot isostatic pressing by the following steps: providing at least one article to be processed inside the load compartment; feeding, via a pressure medium feeding device, a pressure medium into the pressure vessel and increasing the pressure in the load compartment; increasing the temperature in the load compartment; maintaining the increased temperature at a first predetermined temperature level (T 1) for a selected period of time (t 1); maintaining the increased pressure at a first predetermined pressure level (Pi) for a selected period of time (t 2); and thereafter, providing at least one article to be processed inside the load compartment; feeding, via a pressure medium feeding device, a pressure medium into the pressure vessel and increasing the pressure in the load compartment; increasing the temperature in the load compartment; maintaining the increased temperature at a first predetermined temperature level (T 1) for a selected period of time (t 1); maintaining the increased pressure at a first predetermined pressure level (Pi) for a selected period of time (t 2); and thereafter, performing case hardening by the following steps: changing the temperature from the first predetermined temperature level to a second predetermined temperature level (T 2); feeding, via a gas feeding device separate from the pressure medium feeding device, a carbon-containing gas into the pressure vessel; maintaining the second predetermined temperature level for a selected period of time (t 3); reducing the temperature in the load compartment; and discharging the pressure medium from the pressure vessel and reducing the pressure in the load compartment. changing the temperature from the first predetermined temperature level to a second predetermined temperature level (T 2); feeding, via a gas feeding device separate from the pressure medium feeding device, a carbon-containing gas into the pressure vessel; maintaining the second predetermined temperature level for a selected period of time (t 3); reducing the temperature in the load compartment; and discharging the pressure medium from the pressure vessel and reducing the pressure in the load compartment.