temperature is relatively high, restore / repair these
- * Components is commonly more desirable than replacing them when they wear or decompose. The superalloy components of gas turbine engines must generally be passed through a thermal stress relieving process before welding to relax the residual stresses present in the motorcycle service, and then go through a stress relief process afterwards. of welding to relax the residual stresses induced during the cooling of the welding operation. The heat treatment also provides stress relief by dissolving a portion of the priming range (y ') in nickel-base super alloys reinforced with priming range. Generally, the heat treatment parameters will vary depending on the alloy of interest, the amount of residual stress relief and the required dissolution, the design of the furnace, the geometry of the component and many other factors. Increasing rates, impregnation temperatures, holding times and cooling rates for stress relief and dissolution heat treatments are critical to obtain the desired stress relief without adversely affecting superale'acipn and its properties. In the past, heat treatments prior to welding and post-welding have been carried out in large batch heat treatment furnaces in order to increase and maintain a group of components at a suitable heat treatment temperature. After each batch heat treatment, the individual components are welded while being maintained at an elevated temperature (eg, more than about 815 ° C) to improve the welding performances. Welding is generally done in a housing that contains a controlled atmosphere (eg, an inert gas) that uses welding techniques such as Tungsten Inert Gas (TIG) and laser welding processes. Heating is commonly carried out by induction or with the use of lamps, such as quartz halogen lamps. Although it has certain benefits, the disadvantages of using batch heat treatment processes include long heat treatment times due in part to the mass of the large batch oven and the mass of the commonly large number of components that are being heat treated . Additionally, long queuing times occur while batches that are assembled as individual components are repaired. Therefore, the use of stress relieving heat treatments prior to welding and after batch oven welding represents a time delay for the flow of components in a welding line, and is a non-efficient method for Metallurgically condition welding components. In view of the foregoing, it would be desirable that improved processing efficiency could be achieved for superalloy articles manufactured, restored or repaired by welding. BRIEF DESCRIPTION OF THE INVENTION The present invention generally provides a heating apparatus and method for welding a superalloy article. More particularly, the apparatus and method of this invention provide heat treatments prior to welding and post-welding to be performed on an article in the same apparatus in which the welding operation is performed. In view of the criticality of heat treatments prior to welding and post-welding, the invention requires that the welding apparatus be suitably configured to accurately control the temperature of the components being welded. For this reason, the apparatus of this invention generally includes a housing adapted to contain a superalloy article, means for welding the article, means for heating the article in the housing, and means for detecting the temperature of the article in the housing. The apparatus also functions in conjunction with a memory storage device that stores heat treatment temperature profiles prior to welding and subsequent welding and a weld temperature profile for the article. Finally, the apparatus includes a control by means of which the output of the heating medium is adjusted based on the temperature of the article and in accordance with Iq heat treatment temperature prior to welding and after welding and the temperature profile of Welding previously established. The method used by the above-described apparatus generally includes pre-setting the heat treatment temperature profiles prior to the desired welding and post-welding and the welding temperature profile for the superalloy article in question, placing the article in the housing, and then operating the heating, sensing and control means for accurately heating the superalloy article in accordance with the heat treatment temperature profile prior to welding. Once heat has been adequately treated to relieve residual stresses, and without removing the article from the housing, the heating, detection and control means are operated to heat the article directly from the heat treatment temperature profile prior to welding to the welding temperature profile, during which the article is welded. Then, and again without removing the article from the housing, the heating, detection and control means are operated to heat the article directly from the weld temperature profile to the post-weld heat treatment temperature profile. In view of the foregoing, it can be seen that the present invention eliminates the known processing disadvantages for heat treatments prior to welding and after batch welding of articles of superalloys manufactured, restored or repaired by welding. Instead of accumulating a number of items for simultaneous heat treatment, the present invention allows more on-line production of components by combining the heat treatments required with the welding operation in a single apparatus. The invention also reduces the heat treatment durations required by reducing the thermal mass that is being heated and cooled during each heat treatment cycle. Other objects and advantages of this invention will be better appreciated from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic representation of a combination welding and heat treatment apparatus in accordance with this invention; and Figures 2 and 3 are graphs showing the thermal cycles required to heat treat and weld a superalloy article according to the prior art and this invention, respectively. DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to superalloy articles that go through a welding operation during their manufacture, restoration or repair. Although the advantages of this invention are described with reference to the gas turbine engine co-operators, the invention is also applicable to a variety of applications in which an article is to be heat treated before and after welding in a way that does not degrade the properties of the article. An apparatus 10 for performing the heat treatments and the welding operation in accordance with this invention is shown schematically in Figure 1. The apparatus 10 includes a housing 12 generally of a known type for performing a welding operation such as welding laser or by inert gas of Tungsten in a controlled atmosphere. The apparatus also includes a heating device 14 of a known type for heating the interior of the housing 12 during welding. Suitable devices include induction coils, quartz halogen lamps and silicon carbide elements, and may be equipped with cooling elements 16 as shown. The housing 12 also includes an inlet 18 through which an inert gas such as argon is fed into the housing 12 to prevent oxidation of the superalloy article while it is at the high processing temperatures of this invention. An externally cooled heat shield 20 surrounding the housing 12, and an exhaust hood 22 for removing fumes generated during the welding operation are also preferably included. In the past, before welding in a housing of the type shown in Figure 1, a superalloy article was first treated with batch heat to relax the residual stresses present as a result of servicing the article and, if the article is formed of a nickel-based superalloy reinforced with priming range, to provide softening of the alloy by dissolving a portion of the phase and quenching. Then, a second batch heat treatment was performed after welding to relax the residual stresses induced during the cooling of the welding temperatures. These discrete heat treatment cycles are illustrated in Figure 2 as "A" and "C" curves. Curve "B" in Figure 2 represents a welding cycle during which the article is maintained at an elevated temperature, generally more than about 815 ° C. Increasing rates of heating and cooling, impregnation temperatures and holding times for stress relief and dissolution heat treatments are critical to obtain the desired stress relief without adversely affecting the superalloy and its properties. The heat treatment curves A and C include impregnation temperatures at which the article is maintained for a duration sufficient to relieve stresses in the article, for example, approximately twenty to thirty minutes. As a post-welding heat treatment is to be carried out, the temperature and time profile of the welding operations are not as critical, as long as the article is heated to an acceptable temperature prior to welding. As shown by the three discrete temperature profiles of Figure 2, the item being processed is commonly cooled to room temperature between cycles, during which time the item is set aside until sufficient items accumulate to perform a treatment of batch heat. In contrast to the process described above, the welding apparatus 10 of this invention allows the control of the time and temperature profile in the housing 12, and therefore offers the opportunity to perform heat treatments of stress relief prior to welding and after welding and welding. welding in a single furnace using a single thermal exposure of variable temperature, instead of separate welding and batch furnaces that were required in the past. More important, the preferred process carried out in the welding apparatus 10 does not include cooling the article between temperature cycles as shown in Figure 2, but instead cools the article directly from a temperature profile prior to the welding "D" to an "E" weld profile, and then heating the article directly from the weld profile F to a post-weld temperature profile "F", as shown in Figure 3. A comparison of the Figures 2 and 3 show that the profiles prior to welding and post-welding D and F in Figure 3 do not include the constant temperature impregnations characteristic of the corresponding profiles A and C, respectively, of Figure 2. Additionally, the temperatures peak for the profiles prior to welding and after welding D and F in Figure 3 exceed the corresponding impregnation temperatures for profiles A and C, respectively, of Figure 2. The result is not only a reduced cycle time by eliminating cooling at room temperature, but also shorter heat treatment cycles (D and F) before and after welding. However, profiles D and F of Figure 3 and this invention could include impregnations as shown in Figure 2; for example, replacing the impregnations of approximately 1036 ° C shown in Figure 2 for the peaks of approximately 1120 ° C shown in Figure 3. The operational capabilities shown above are achieved by sensing the temperature of the article in housing 12 with a sensor of suitable temperature 24, such as an optical pyrometer or a standard K-type thermocouple. The temperature signal of the sensor 24 is used as an input to a programmable temperature controller 26, which compares the signal from the sensor 24 to the desired profiles D, E and F stored in the memory 28 for the article. Then, the control signal is regulated to the heating device 14 based on the difference between the desired temperature profile and the temperature of the article. In this way, essentially any temperature profile required for a given superalloy article can be precisely programmed and controlled to achieve the objects of this invention. In view of the foregoing, it can be seen that the present invention provides for the integration of heat treatment and welding cycles into a single apparatus, with the result that what were previously three discrete temperature profiles are now consolidated in a single exposure thermal Advantages include the elimination of batch heat treatments, the elimination of cooling at room temperature between treatments, and the reduction of individual treatment profiles. Although described in terms of certain equipment for processing superalloy articles, apparatus 10 of this invention could also be used for the treatment and welding of other materials and articles whose processing requires precise control at elevated temperatures to avoid degradation. of the properties of the article. Therefore, although the invention has been described in terms of a preferred embodiment, it is clear that those skilled in the art could take other forms. Accordingly, the scope of the invention is limited only by the following claims.