Juan Carlos Cruz-Robles
DM3D Technology LLC
Auburn Hills, MI
Direct metal deposition, an additive manufacturing technology, has made it possible to add a high-carbon steel to the area of contact of a tool steel punching tool in order to change the properties and behavior of the tool. Hardness and wear resistance were tested and the technology demonstrated its potential to add dissimilar materials to change the properties of a tool or component.
Improvement in the performance of a cylindrical punching tool for hardness and wear resistance was tested after the use of direct metal deposition (DMD) to deposit an additional material on the tool surface. DM3D Technology has been working for several years improving the technology DMD, which is capable of melting gas atomized metal powders with a power laser over a substrate layer by layer. The technology allows the possibility of using one or several materials to build a 3D part, repair an existing component, or deposit over a surface to obtain desired properties. Some of the main characteristics of this technology that distinguish it from others is its capability of allowing fully dense metal structures, controllable microstructures, and heterogeneous material fabrication as well as near net shape geometry generation.
The first figure shows a general overview of a DMD system that contains a laser system, a powder feeding system, shielding and cover gases for oxidation and transportation of powders, and feedback sensors to control the deposition process. Particularly for the purpose of the experiments described in this paper, a DMD machine with a CO2 laser controlled by a three-axis CNC system from DM3D Technology was used.
The tool steel punches used were supplied by Dayton Lamina Corp. The punch used for this study is originally made out of a tool steel with a hardness of 54 HRC [1, 2]. In order to increase its service life, a higher carbon content tool steel—to improve wear resistance and even further the toughness—was deposited by DMD. A complete part body, indicating the top face area where the high carbon steel deposition was made, is shown in the second figure. Due to the nature of this process, the surface roughness usually is as good as a sand casting; therefore, depending on the specification of the part, some finishing can be done afterward.
A metallographic analysis was performed on a cross section of the punch to show the full metallurgical bond between the punch and the high-carbon steel. In this analysis, an average deposition thickness of 544 µm was found, which is observed in the third figure, which shows the right corner from the two edges of the cross section analyzed.
Some characteristics found in this analysis were a fine grain structure and an improvement in hardness by 10% compared with the tested hardness on the current tool steel. In the fourth figure can be seen the harness behavior along a diagonal line from the edge of the punch left corner section. The different harnesses shown consistency in most of the deposition, which gives confidence for DMD to control the microstructures.
With a considerable improved hardness, the punch treated will show an increment on its compressive strength, which will be beneficial for its tool life. This material addition not only works as an improvement to the tool steel toughness but also to wear resistance. The minimum heat-affected zone between the two alloys showed that the properties of the original punch were as close as the material specification immediately after the interface.
Wear behavior was tested on the post-DMD punch as compared with standard tool steel. Experiments were carried out in a pin-on-disk setup under 30 N (6.7 lb) load and 22.15 m/min. (872 IPM) speed at room temperature. These results showed a reduction of 80% in depth of wear between the two punches and can be observed in the fifth figure.
Results like this show DMD as a value-added technology that can lead to considerable cost reductions by allowing a component to be built with a non-expensive alloy and adding the required alloy only on the needed areas. Also, this concept can be easily applied on used and worn components to increase tool life.
In conclusion, the main advantages of DMD technology for hard surfacing over conventional manufacturing processes are:
- Ability to add dissimilar materials, allowing different properties on desired areas, resulting in cost reductions.
- Low heat-affected zones.
- Low distortion of the part due to laser low heat input.
This Web feature is part of the contents of Aerospace & Defense Manufacturing 2015, available in September 2015.
Published Date : 8/13/2015