Method and apparatus for introducing normally solid material into substrate surfaces
AssigneePlaur Corporation
InventorZhong Xu
Life of this patent
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Abstract
Method and apparatus for introducing normally solid metals or metalloids into electrically conductive substrates. The invention is particularly useful in surface alloying of metal substrates and makes it possible to introduce metals into ferrous metal substrates to depths of 200 microns and more. The metal or metalloid to be introduced is maintained at an elevated temperature below the boiling point, the surface portion of the substrate is maintained at an elevated temperature below the deformation point, and a double glow discharge is employed under controlled conditions to transfer the metal or metalloid to the substrate.
Claims30
The method for introducing into an electrically conductive substrate at least one normally solid material selected from the group consisting of metals and metalloids, the method producing an alloy of the at least one normally solid material penetrating below the surface of the substrate, the method comprising the steps of:
- providing a closed chamber in which the atmosphere and pressure can be controlled and which includes an anode;
- positioning the substrate as a cathode with the surface of the substrate exposed to the interior of the chamber and spaced from the anode;
- providing a source electrode comprising a body of the material to be introduced into the substrate,
- said body being exposed within the chamber in a location spaced from the anode and the substrate;
- evacuating the chamber and establishing therein an atmosphere of inert gas at a pressure not exceeding 10 torr;
- establishing a direct current potential difference between the anode and the cathode and a direct current potential difference between the anode and the source electrode to cause a double glow discharge with one glow discharge occurring between the anode and cathode and the other between the anode and the source electrode and maintaining the double glow discharge for a time period of at least 1 minute;
- and
- maintaining the surface portion of the substrate at an elevated temperature not exceeding the deformation point of the substrate and maintaining said body of material at a temperature below the boiling point of the material,
- said temperatures being maintained throughout said time period;
- the double glow discharge causing said body of material to be bombarded by ions of the inert gas of the atmosphere with resultant heating of the said body and ejection of positive ions of the material of said body from said body,
- the positive ions so ejected travelling to the substrate and vigorously bombarding the exposed surface of the substrate,
- such bombardment causing the metal ions to penetrate the exposed surface of the substrate and permeate a portion of the heated substrate below said surface to thereby form said alloy penetrating below the surface of said substrate.
In an apparatus for introducing into an electrically conductive substrate at least one normally solid material selected from the group consisting of metals and metalloids, the combination of
- means defining a sealed chamber;
- means for evacuating the chamber;
- means for establishing in the evacuated chamber an inert gas atmosphere at a pressure of 0.01-10 torr,
- an anode exposed to the interior of the chamber, the substrate being arranged as a cathode with the surface of the substrate exposed to the interior of the chamber and spaced from the anode;
- a source electrode comprising a body of the material to be introduced in to the substrate,
- said body being disposed in the chamber in a location spaced from the anode and the substrate;
- means for establishing between the anode and the substrate a first direct current potential difference in excess of the glow discharge inception voltage for the inert atmosphere and pressure;
- means for establishing between the anode and the source electrode a second direct current potential difference of the same polarity, whereby glow discharge operation in the abnormal range will result in a first glow discharge between the anode and the cathode and a second glow discharge between the anode and the source electrode;
- and
- means external to the chamber for heating said body,
- whereby an alloy of the at least one normally solid material penetrating below the surface of the substrate is created,
- whereby the double glow discharge causes said body of material to be bombarded by ions of the inert gas of the atmosphere with resultant heating of said body and ejection of positive ions of the material of said body from said body, and
- whereby the positive ions so ejected travelling to the substrate vigorously bombard the exposed surface of the substrate as a rsult of the difference in charge between the positive ions and the substate, and whereby the metal ions penetrate the exposed surface of the substrate and permeate a portion of the heated substrate below said surface to thereby form said alloy penetrating below the surface of said substrate.
Dependencies are inferred from the claim text.