Machining of aluminum surfaces
View Patent ↗Machining of aluminum workpieces with diamond or diamond-like carbon-surface coated tools may be conducted in an atmosphere containing hydrogen gas at a partial pressure effective for hydrogen to react with carbon atoms at the surface to form C—H bonds that resist adherence of aluminum to the tool surface. Suitably, hydrogen or a hydrogen-containing gas mixture is confined at the interface of tool and workpieces at the machining site. Hydrogen partial pressure may be determined for a tool-workpiece-machining temperature combination by calculation or experiment.
1. A method of dry machining an aluminum alloy workpiece with a tool having a carbon material cutting surface, the carbon material being characterized by sp 2 and/or sp 3 carbon-to-carbon bonding, the method comprising:
bringing the aluminum alloy workpiece and carbon material cutting surface of the tool into machining engagement in which the tool removes aluminum material from the workpiece; and
continually maintaining an atmosphere containing hydrogen gas at the region of machining engagement, the atmosphere presenting sufficient hydrogen partial pressure at the tool-workpiece engaging surfaces, at the temperature of the engaging surfaces, to form and maintain a hydrogenated carbon layer on the carbon material cutting surface for minimizing adherence of aluminum to the carbon cutting surface.
2. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the minimum hydrogen partial pressure is at least the value determined by the following:
p
H
2
=
ⅇ
-
0.68875
-
μ
(
T
)
8.62
×
10
-
5
T
×
1.01
×
10
5
Pa
,
where
μ
(
T
)
=
(
53.65
T
-
1.66
×
10
-
3
T
2
-
27.37
T
ln
T
)
×
1.04
×
10
-
5
-
0.0483
,
and where T is the absolute temperature in Kelvin.
3. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 further comprising controlling the temperature of the tool and maintaining a hydrogen partial pressure for ongoing formation of the hydrogenated carbon on the carbon material cutting surface at the controlled temperature.
4. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 further comprising periodically measuring the temperature of the tool and adjusting, if and as necessary, the hydrogen partial pressure for ongoing formation of the hydrogenated carbon on the carbon material cutting surface at the measured temperature.
5. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the carbon material cutting surface initially comprises a non-hydrogenated diamond-like carbon coating.
6. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the carbon material cutting surface comprises diamond.
7. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the carbon material cutting surface comprises CVD diamond coating.
8. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the aluminum alloy surface comprises aluminum-silicon alloy.
9. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the tool is a drill.
10. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the atmosphere containing hydrogen gas is enclosed around the region of machining engagement.
11. A method of dry machining an aluminum alloy workpiece as set forth in claim 1 wherein the atmosphere containing hydrogen gas also contains an inert gas.
12. A method of dry machining an aluminum alloy workpiece as set forth in claim 11 wherein the inert gas comprises one of helium, nitrogen, or argon.