Patent Application
20130344344
This disclosure relates to a method of forming a composite article, such as a tool, agricultural implement, vehicle component or the like.
Components that are subject to wear often include a wear-resistant coating to extend the life of the component. There are a variety of different techniques by which the coating can be applied. As an example, a wear-resistant coating can be applied using a spray-welding technique, such as flame or plasma spraying. Alternatively, the coating can be applied using a powder technique. The powder technique involves applying an aqueous slurry of a powder material onto the component and multiple heating processes to serve the functions of removing solvent, removing binder agents, consolidating the powder and fusing the consolidated powder to the component. The multiple heating processes are necessary because the conditions that serve each function differ.
A method for forming a composite article includes providing a metallic substrate and a preform adjacent the metallic substrate. The preform includes an unfused metallic powder material with an organic binder dispersed through the powder material. The metallic substrate and the preform are then subjected to a monocyclic heating process. The monocyclic heating process causes removal of the organic binder from the preform, fusing of the metallic powder material and metallurgical bonding of the metallic powder to the metallic substrate.
In another aspect, a method for forming a composite article includes providing an iron-based substrate that has a first hardness and providing a preform adjacent the iron-based substrate. The preform includes an unfused metallic powder material with an organic binder dispersed through the powder material. The iron-based substrate and the preform are then subjected to a monocyclic heating process that converts the preform into a wear-resistance element. The wear-resistance element has a second, greater hardness and is metallurgically bonded on the iron-based substrate.
Also disclosed is an article that is ready for forming a composite with a metallic substrate. The article includes a preform having an unfused metallic powder material with an organic binder dispersed there through.
The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
Disclosed herein is a method 10 for forming a composite article. The method 10 will be described with regard to the flow chart shown in
The method 10 includes step 12 of providing a metallic substrate 20 and a preform 22, as shown in
The preform 22 is arranged adjacent the metallic substrate 20 (see
As shown in a modified example in
The method 10 further includes a heating step 14. As depicted in
As shown in
In a further example, the composition of the metallic powder material 24 of the preform 22 is selected such that the resulting dense element 30 serves as a wear-resistance element. In this regard, the metallic substrate 20 defines a first hardness and the dense element 30 defines a second, greater hardness such that the dense element 30 effectively provides a reduced wear rate and protects the underlying metallic substrate 20 from abrasion and the like. The thickness of the preform 22 corresponds to the final thickness of the dense element 30. Relatively thick dense elements can be produced using the disclosed method, without the use of multiple coating passes and waste of materials in comparison to aqueous slurry techniques.
As an example, the metallic substrate 20 is an iron-based material, such as steel, and the metallic powder material of the preform 22 has a composition that is substantially harder and more wear-resistant than the metallic substrate 20. The composition of the metallic powder material, and thus the dense element 30, has a Knoop hardness value in the range of 800 to 1400. In a further example, the metallic powder material 24 is a nickel-based alloy, cobalt-based alloy or iron-based alloy. Additionally, the selected alloy can further include 0.1-20% by weight of boron, carbon, chromium, iron (in nickel and cobalt based alloys) manganese, nickel (in iron and cobalt based alloys), silicon, tungsten or combinations thereof. In a further example, the nickel, cobalt or iron is present in 60% by weight or more in the above compositions. In a further example, the composition of the metallic powder material is an example composition set forth in the Table below.
As used in this disclosure, the term “monocyclic heating process” refers to a heating process that includes only one temperature ramp-up and only one temperature ramp-down.
The temperatures and heating rates of the ramp-up portion 40, the ramp-down portion 42 and the hold or soak portion 44 depend on the materials selected for the unfused metallic powder 24 and metallic substrate 20. In examples based on using an iron-based material as the metallic substrate 20 and nickel-based, cobalt-based or iron-based alloys for the metallic powder 24, the ramp-up portion 40 may have a predetermined heating rate and may optionally include one or more hold portions prior to the soak portion 44, to facilitate binder removal, for example. The soak portion 44 may be at a temperature of approximately 1100° C. for a predetermined amount of time, to promote solid state fusion of the metallic powder 24 and metallurgical bonding of the metallic powder 24 and the metallic substrate 20. The ramp-down portion 42 may have a controlled, prescribed cooling rate or natural cooling rate obtainable in ambient air.
The monocyclic heating process 28 thus enhances process efficiency and lowers cost in comparison to multicycle heating processes that involve multiple temperature ramp-ups and ramp-downs because less energy, such as electrical energy, is required. Moreover, the monocyclic heating process 28 also involves less labor in handling work pieces, which also further reduces costs in comparison with a multicycle heating process that require additional handling.
In a further example, the monocyclic heating process 28 includes heating the metallic substrate 20 and the preform 22 in a furnace or chamber 50 (
In a further example, the pressure of the environment 52 within the furnace or chamber 50 is controlled to establish a substantially atmospheric pressure. As an example, the pressure within the furnace or chamber 50 is established at atmospheric pressure +/−100%. In some examples, the pressure of the environment 52 may thus be slightly positive to ensure that outside gases do not tend to leak into the furnace or chamber 50.
The method of forming the composite article can further include forming the preform 22, although the preform 22 could be independently provided. As an example, the forming of the preform 22 includes providing the unfused metallic powder material 24 and the organic binder 26 in a mixture and consolidating the mixture to form the preform 22.
The technique used for consolidating can vary depending upon the desired shape of the preform 22. In one example, the technique includes consolidating the mixture under pressure, and optionally heat, to form the desired shape of the preform 22. In an alternate example, the mixture is extruded. It is to be understood, however, that other techniques may alternatively be used to form the preform 22 into a desirable shape. In that regard, it is to be understood that the preform 22 can be shaped to correspond to the shape of the metallic substrate 20 in the area to which the preform 22 is to be bonded. That is, the preform 22 generally conforms to the shape of the surface of the metallic substrate 20 such that there is relatively close or intimate contact between the preform 22 and the metallic substrate 20 in the monocyclic heating process 28.
The average size of the particles of the metallic powder material 24 is selected for enhanced fusing and metallurgical bonding in the monocyclic heating process 29. In comparison, in slurry-based techniques, relatively small particle sizes are used to obtain desired slurry properties. However, since the preform 22 of the present disclosure is not formed using a slurry-based technique and can be formed separate from the presence of the metallic substrate 20, the average particle size can be relatively larger such that quality fusing and bonding can be achieved in the monocyclic heating process 28. In one example, the unfused metallic powder material 24 has an average particle size of greater than 45 micrometers.
Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.
