Low pressure induction carburization

#The present disclosure generally relates carburization technologies.

#The art of carburization has experienced several technological challenges over the years. One challenge relates to the cycle time required to create carburized articles. Currently, one industry standard and common way to case-harden articles of manufacture is by using the furnace carburization process. Articles are batched into a carburized atmosphere furnace, heated to the correct temperature and for the correct time to establish a specified case depth hardness. Before carburizing, articles are strategically/selectively plated with copper to avoid carburization of surfaces of the article that should not be hardened. A typical carburization heat treat process may take approximately 3-5 hours. If one includes the additional time required for plating, stripping, masking, sand blast, and final stripping processes, the overall cycle time may take 5 to 15 days. Further, furnaces are automated for material handling and running the correct heat treat recipe. Once the furnaces are started, they must run continuously to avoid damaging the fire brick interior and affect the furnace longevity. As such, furnace carburization technologies are time intensive and require significant unproductive energy.

#Another challenge relates to the deformation of articles caused by the carburization process. Article manufacturers typical encounter part distortion due to the adverse effects caused from the heat treatment of parts during the case hardening and through hardening processes. Historically, heat treat distortion in articles has caused major yield issues and affects every step of the manufacturing process after heat treat. Typically, non-clean up (NCU), outer dimension (OD) undersized and inner dimension (ID) oversized are common part defects found on articles due to the heat treat process.

#The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

#FIG. 1 is a flow diagram illustrating steps in a method for selective carburization of an article using low pressure induction carburization in accordance with embodiments of the present disclosure;

#FIG. 2 illustrates an experimental test apparatus for testing selective carburization of a gear article using low pressure induction carburization in accordance with embodiments of the present disclosure;

#The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.

#The present disclosure relates to the selective carburization of articles using low pressure induction carburization. As used herein the term “carburization” is intended to mean a heat treatment process in which iron or an iron alloy, such as steel, absorbs carbon liberated when the metal is heated in the presence of a carbon bearing material, such as acetylene, ethylene, methane, charcoal, carbon monoxide, etc., with the intent of making the metal harder. Depending on the amount of time and temperature, the affected area can vary in carbon content.

#As used herein, the term “article” is intended to mean any object that is susceptible to the carburization process. Examples of these objects include, by way of non-limiting example, gears, shafts, plates, bearings, blades, fins, rods, valves, and coils, among many other possible examples. Susceptibility to carburization indicates that the object is made of a material that may be carburized, non-limiting examples of which include iron or the various iron alloys, of which a principle class thereof is steel.