Layered construction of in-situ metal matrix composites

1. A method of layer-by-layer construction of a metallic part comprising:

supplying particles of an alloy, wherein said alloy consists of Fe at a level of 50.0 to 76.0 wt. %; B at 0.5 to 3.0 wt. %; Cr at 15.0 to 22.0 wt. %; Si at 2.0 to 5.0 wt. %; Ni at 5.0 to 15.0 wt. %; optionally C at 0.0 to 0.5%, optionally Mn at 0.3 to 3.0 weight %, and unavoidable impurities;

supplying a substrate;

applying said alloy onto said substrate by melting said particles of said alloy into a molten state and cooling to form a solidified layer of said alloy and repeating to form successive solidified layers of said alloy, wherein each of said solidified layers of said alloy has a thickness as formed of 3.0 to 200.0 microns;

heat treating said solidified layers of said alloy in a vacuum atmosphere, an inert gas atmosphere, a reducing gas atmosphere, or an atmosphere comprising a mixture of inert and reducing gases;

optionally removing said substrate to form a free-standing metallic part; and

wherein one or more solidified layers of said alloy has an abrasion resistance as measured by ASTM G65-04(2010) Procedure A of less than or equal to 175 mm 3 .

2. The method of claim 1 wherein said cooling is in the range of 10 3 to 10 8 K/sec.

3. The method of claim 1 wherein said solidified layer after cooling defines a primary dendritic austenite phase and an initial level of interdendritic lamellar boride phases with lamella width of less than 0.1 microns, and upon heating, said boride phases consolidate and grow by diffusion of said elements from said primary phase into spheroidized boride phases ranging in diameter from about 0.2 micron to 5 microns.

4. The method of claim 1 wherein said heat treatment comprises heating at a temperature in the range of 800 to 1200° C. for a time period of 30-1000 minutes.

5. The method of claim 1 wherein said alloy consists of Fe at 55.5 to 71.5 wt. %; B at 0.5 to 3.0 wt. %; Cr at 15.0 to 20.0 wt. %; Si at 2.0 to 5.0 wt. %; Ni at 11.0 to 15.0 wt. %; optionally C in an amount up to 0.5 wt. %, and unavoidable impurities.

6. The method of claim 1 wherein said alloy consists of Fe at 55.5 to 75.2 wt. %; B at 0.5 to 3.0 wt. %; Cr at 17.0 to 22.0 wt. %; Mn at 0.3 to 3.0 wt. %; Si at 2.0 to 5.0 wt. %; Ni at 5.0 to 10.0 wt. %; optionally C in an amount up to 0.5 wt. %; and unavoidable impurities.

7. The method of claim 1 wherein said alloy consists of Fe at 54.5 to 69.5 wt. %; B at 0.5 to 3.0 wt. %; Cr at 16.5 to 20.5 wt. %; Mn at 1.0 to 2.5 wt. %; Si at 2.0 to 5.0 wt. %; Ni at 10.5 to 14.0 wt. %; optionally C in an amount up to 0.5 wt. %; and unavoidable impurities.

8. The method of claim 1 wherein said metallic part comprises a pump or pump parts, valve, mold, bearing, cutting tool, filter, or screen.

9. The method of claim 1 , wherein said particles have a diameter of 15.0 to 70.0 microns.

10. The method of claim 1 , wherein said particles have a diameter of 20.0 to 45.0 microns.

11. The method of claim 1 , wherein heat treating said one or more layers of said alloy is performed in a vacuum atmosphere.

12. The method of claim 1 , wherein heat treating said one or more layers of said alloy is performed in an inert gas atmosphere.

13. The method of claim 1 , wherein heat treating said one or more layers of said alloy is performed in a reducing gas atmosphere.

14. The method of claim 1 , wherein said alloy consists of one of the following compositions (a) or (b):

(a) Fe at 54.5 to 69.5 wt. %; B at 0.5 to 3.0 wt. %; Cr at 16.5 to 20.5 wt. %; Mn at 1.0 to 2.5 wt. %; Si at 2.0 to 5.0 wt. %; C at 0.0 to 0.5 wt. %; Ni at 10.5 to 14.0 wt. %, and inevitable impurities;

(b) Fe at 55.5 to 75.2 wt. %; B at 0.5 to 3.0 wt. %; Cr at 17.0 to 22.0 wt. %; Mn at 0.3 to 3.0 wt. %; Si at 2.0 to 5.0 wt. %; C at 0.0 to 0.5 wt. %; and Ni at 5.0 to 10.0 wt. %, and inevitable impurities.

15. The method of claim 1 , wherein melting said particles of said alloy into a molten state is performed with a laser or an electron beam.