Reducing surface asperities

Patent metadata

Field	Value
Publication number	US-10315275-B2
Application number	US-201313749426-A
Country	US
Kind code	B2
Filing date	Jan 24, 2013
Priority date	Jan 24, 2013
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

Surface asperities, such as roughness characteristics, are reduced or otherwise mitigated via the control of surface regions including the asperities in different regimes. In accordance with various embodiments, the height of both high-frequency and low-frequency surface asperities is reduced by controlling characteristics of a surface region under a first regime to flow material from the surface asperities. A second regime is implemented to reduce a height of high-frequency surface asperities in the surface region by controlling characteristics of the surface region under a second regime to flow material that is predominantly from the high-frequency surface asperities, the controlled characteristics in the second regime being different than the controlled characteristics in the first regime. Such aspects may include, for example, controlling melt pools in each regime via energy pulses, to respectively mitigate/reduce the asperities.

First claim

What is claimed is:

1. A method comprising:
reducing a height of surface asperities in a material surface region having both high-frequency surface asperities and low-frequency surface asperities, by controlling characteristics of the surface region under a first regime to flow material from the surface asperities; and
reducing a height of high-frequency surface asperities in the material surface region by controlling characteristics of the surface region under a second regime to flow material that is predominantly from the high-frequency surface asperities, the controlled characteristics in the second regime being different than the controlled characteristics in the first regime.

2. The method of claim 1 , wherein
reducing the height of the surface asperities under the first regime includes reducing the height of both high-frequency and low-frequency surface asperities by iteratively generating and solidifying melt pools at different portions of the material surface region; and
reducing the height of the high-frequency surface asperities under the second regime includes reducing a height of high-frequency surface asperities generated by the iterative generation and solidification of the melt pools under the first regime, by iteratively generating and solidifying additional melt pools in the material surface region.

3. The method of claim 1 , wherein
controlling characteristics of the surface region under the first regime includes setting a first temperature gradient at the surface region and using the first temperature gradient to heat and promote the material flow; and
controlling characteristics of the surface region under the second regime includes setting a second temperature gradient at the surface region, the second temperature gradient being different than the first temperature gradient, and using the second temperature gradient to heat and promote the flow of the material that is predominantly from the high-frequency surface asperities.

4. The method of claim 1 , wherein
controlling characteristics of the surface region under the first regime includes generating and using first energy pulses to flow the material; and
controlling characteristics of the surface region under the second regime includes generating and using second energy pulses that are different than the first energy pulses, to flow the material that is predominantly from high-frequency surface asperities generated under the first regime, while leaving material that predominantly corresponds to low-frequency surface asperities.

5. The method of claim 4 , wherein at least one of generating and using the first energy pulses and generating and using the second energy pulses includes applying energy pulses to a portion of the surface region to
generate a melt pool in the surface region during the application of each energy pulse, and
solidify the melt pool during a period between each energy pulse.

6. The method of claim 5 , wherein generating a melt pool in the surface region during the application of each energy pulse includes
for the first energy pulses, maintaining the melt pool for a first time period by applying pulses of a first duration, and
for the second energy pulses, maintaining the melt pool for a second time period that is different than the first time period, by applying pulses of a second duration that is different than the first duration.

7. The method of claim 5 , wherein generating and using the first energy pulses includes generating and using energy pulses at first duty cycle and first repetition rate that maintain the melt pool for a first time period; and
generating and using the second energy pulses includes generating and using energy pulses at a second duty cycle and second repetition rate that are different than the first duty cycle and first repetition rate, and that maintain the melt pool for a second time period that is different than the first time period.

8. The method of claim 7 , wherein the steps of generating and using first and second energy pulses respectively include generating heat pulses with a laser operated at the respective duty cycles and repetition rates.

9. The method of claim 4 , wherein generating and using the first energy pulses includes generating and using energy pulses that are different than the second energy pulses in at least one of: duty cycle and repetition rate, power, pulse duration, time between pulses, and intensity distribution of the energy pulses in the surface region.

10. The method of claim 4 , wherein
generating and using the first energy pulses includes using the first energy pulses to set a first surface tension condition that varies along the surface region, and using the first surface tension condition to promote the flow of the material; and
generating and using the second energy pulses includes using the second energy pulses to set a second surface tension condition that varies along the surface region, the second surface tension condition being different than the first surface tension condition, and using the second surface tension condition to promote the flow of the material.

11. The method of claim 4 , wherein generating and using at least one of the first and second energy pulses includes generating energy pulses based upon a type of surface feature in the surface region, and using the energy pulses to reduce a height of surface features of the type in the surface region.

12. The method of claim 1 , wherein
controlling characteristics of the surface region under the first regime includes setting a first surface tension condition that varies along the surface region and using the first surface tension condition to promote the flow of the material under the first regime; and
controlling characteristics of the surface region under the second regime includes setting a second surface tension condition that varies along the surface region, the second surface tension condition being different than the first surface tension condition, and using the second surface tension condition to promote the flow of the material under the second regime.

13. The method of claim 12 , wherein at least one of setting a first surface tension condition and setting a second surface tension condition includes using a dopant at the surface region to set the surface tension condition.

14. The method of claim 12 , wherein at least one of setting a first surface tension condition and setting a second surface tension condition includes using a surface-active agent located at a surface of the surface region, to set the surface tension condition.

15. The method of claim 1 , wherein reducing a height of surface asperities and reducing a height of high-frequency surface asperities include reducing the height of surface asperities while removing substantially none of the material in the surface regions.

16. A method comprising:
reducing a height of both high-frequency surface asperities and low-frequency surface asperities in a surface region of a material, by
applying first energy pulses to generate melt pools in the surface region and to promote thermocapillary flow of the material from the surface asperities in the melt pools, and
via the thermocapillary flow, generating additional high-frequency asperities near edges of the melt pools as the melt pools solidify; and

reducing a height of the additional high-frequency asperities under a second regime by applying second energy pulses to generate melt pools in the surface region and to promote at least one of thermocapillary flow and capillary flow of the material from the additional high-frequency asperities, the seco

Assignees

• Wisconsin Alumni Res Found

Inventors

• Vadali Venkata Madhukanth
• Ma Chao
• Duffie Neil Arthur
• Li Xiaochun
• Pfefferkorn Frank Ewald

Classifications

• B23K26/354 Primary

  by melting · CPC title

• B23K26/3576

  Diminishing rugosity, e.g. by grinding, polishing or smoothing · CPC title