The present invention relates generally to the production of a metal work piece with improved surface durability.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
Work piece components are often subject to wear and abrasion during use or operation in a variety of environments. Currently various methods are provided for improving surface wear durability by nitriding, carburizing, quenching, surface coating, cladding and centrifugal casting with hard carbides injected into the melt. Such methods are limited by reaction kinetics, diffusion kinetics, formation of undesirable phase, inhomogeneity due to concentration gradients and thermodynamic stability of the phases of interest at high treatment temperatures. Workpiece distortion is a typical consequence of the aforesaid high treatment temperatures. It is therefore an important object of the present invention to provide for surface treatment of work piece components which avoids the problems and disadvantages heretofore associated therewith.
Pursuant to the present invention, the durability of the surface of a metallic work piece substrate, subject to wear and corrosion, is improved by influx of hard particles into the substrate within which dispersion of the particles is effected by rotation of a friction stir welding type tool under axial pressure having a protrusion inserted into the substrate to effect mixing. Various different methods may be utilized for influx of the hard particles. The hard particles may be transferred from a layer deposited onto the substrate surface or may be injected from some external source. The hard particles could also be derived and delivered by ablation of the friction stir tool during use. A layer of the hard particles may be laminated with layers of base metal before being mixed by the tool to transfer the particles into the surfaces. Finally the hard particles may be injected from an external source through a central hole in the tool extending along its axis.
A more complete appreciation of the invention and many of its attendant advantages will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:
Referring now to the drawing in detail,
The hard particles within the deposited layer 32 is composed of a chemically selected material which will substantially improve properties of the metallic surface 28, such as wear resistance, heat resistance and corrosion resistance, as a result of the aforesaid stir mixing within the zone 30. The stirring tool 10 undergoes shift in a feed direction 34 as denoted in
According to another embodiment of the present invention as diagrammed in
The construction of the stirring tool 10 as hereinbefore described insures adequate performance of the surface treatment process by adequate dispersion of the hard particles introduced into the metal substrate component 12 either by transfer from the deposited layer 32 or injection from the external source 36 wherein the disintegration of the particles occurs with or without ablation and erosion. Only after such dispersion has occurred, so as to effect an increase in durability and an improvement in other physical properties of the metal substrate surface 28, the tool 14 may be replaced.
Referring now to
Obviously, other modifications and variations of the present invention may be possible in light of the foregoing teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
Number | Name | Date | Kind |
---|---|---|---|
4959241 | Thomas et al. | Sep 1990 | A |
6543671 | Hatten et al. | Apr 2003 | B1 |
6634199 | Nomura et al. | Oct 2003 | B1 |
6726085 | Litwinski et al. | Apr 2004 | B1 |
6905060 | Van Aken et al. | Jun 2005 | B1 |
20040265503 | Clayton et al. | Dec 2004 | A1 |
20050045695 | Subramanian et al. | Mar 2005 | A1 |
20050242158 | Bolser | Nov 2005 | A1 |