Fabrication method for a component having magnetic and non-magnetic dual phases
Methods for forming a dual-phase magnetic component from an initial component comprising a non-magnetic austenite composition are provided. The method may include: forming a coating on a portion of the surface of the initial component to form a masked area while leaving an unmasked area thereon. Thereafter the initial component may be heated to a treatment temperature such that nitrogen diffuses out of the unmasked area of the initial component to transform the non-magnetic austenite composition to a magnetic phase in the unmasked area. Thereafter, the initial component may be cooled from the treatment temperature to form a dual-phase magnetic component having a magnetic region corresponding to the unmasked area and a non-magnetic region corresponding to the masked area.
1. A method of forming a dual-phase magnetic component from an initial component comprising a non-magnetic austenite composition and having a surface, the method comprising:
forming a coating on a portion of the surface of the initial component to form a masked area while leaving an unmasked area thereon;
thereafter, heating the initial component to a treatment temperature such that nitrogen diffuses out of the unmasked area of the initial component to transform the non-magnetic austenite composition to a magnetic phase in the unmasked area; and
thereafter, cooling the initial component from the treatment temperature to form a dual-phase magnetic component having a magnetic region corresponding to the unmasked area and a non-magnetic region corresponding to the masked area.
2. The method of claim 1 , wherein nitrogen is retained in the unmasked area of the initial component during heating the initial component to the treatment temperature such that the masked area retains the non-magnetic austenite composition.
3. The method of claim 1 , wherein the treatment temperature is greater than 1000° C.
4. The method of claim 1 , wherein the treatment temperature of 1100° C. to 1300° C.
5. The method of claim 1 , wherein cooling the initial component from the treatment temperature is performed at a cooling rate sufficiently fast to retain both magnetic and non-magnetic phases formed during heating.
6. The method of claim 1 , wherein the heating the initial component is performed at a treatment pressure of less than 1 atmosphere.
7. The method of claim 1 , wherein the heating the initial component is performed at a treatment pressure of less than 0.5 atmosphere.
8. The method of claim 1 , wherein the coating comprises chromium oxide.
9. The method of claim 1 , wherein the non-magnetic austenite composition comprises an iron alloy that includes chromium, manganese, and nitrogen.
10. The method of claim 9 , wherein heating the initial component is performed in an oxygen-deficient atmosphere to inhibit formation of chromium oxide on the unmasked area.
11. The method of claim 1 , further comprising:
after cooling the initial component from the treatment temperature, removing the coating from the dual-phase magnetic component.
12. The method of claim 11 , wherein removing the coating comprises mechanically or chemically removing the coating from the dual-phase magnetic component.
13. The method of claim 1 , wherein the non-magnetic austenite composition that has a nitrogen concentration that is greater than 0.4% by weight.
14. The method of claim 13 , wherein the non-magnetic austenite composition that has a nitrogen concentration that is greater than 0.5% by weight.
15. The method of claim 13 , wherein the magnetic region of the dual-phase magnetic component has a nitrogen concentration that is less than 0.4% by weight.
16. The method of claim 13 , wherein the magnetic region of the dual-phase magnetic component has a nitrogen concentration that is less than 0.1% by weight.
17. The method of claim 1 , wherein the coating comprises a chromium oxide, aluminum-silicate materials, aluminide silicide materials, or mixtures thereof.
18. The method of claim 1 , wherein the coating has a thickness of 125 μm or less.
19. The method of claim 1 , wherein the coating has a thickness of 10 μm to 100 μm.
20. The method of claim 1 , wherein heating the initial component to the treatment temperature is performed in a furnace cavity with continuous evacuation of nitrogen from the furnace cavity.