Custom titanium alloy for 3-D printing and method of making same

Abstract

A Ti-6A1-4V titanium powder alloy composition having enhanced strength resulting from the addition of one or more of the following elements without requiring an increase in oxygen content: Aluminum Iron Nitrogen Carbon The composition may also be used for Ti-6A1-4V titanium alloy starting bar stock.

Claims

1. A method of increasing the strength of Ti-6A1-4V titanium alloy powder or starting bar stock without increasing oxygen content, comprising adding to the powder or starting bar stock the following combination of elements: Aluminum Iron Nitrogen Carbon, wherein the weight percent of the elements for the bar stock is: Aluminum6.3% to 6.7% Iron0.15% to 0.30% Nitrogen0.02% to 0.05% Carbon0.04% to 0.08%.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Table 2 illustrates the specification for Ti-6A1-4V titanium powder alloy with aluminum, iron, nitrogen and carbon composition ranges that, when combined, provide the desired strength enhancement in the alloy without high initial oxygen content. Therefore the baseline strength of 3-D printed Ti-6A1-4V parts produced with this Ti-6A1-4V composition would be similar to higher oxygen Ti-6A1-4V and the Grade 5 parts but would have the low oxygen desired for maximum re-use of the powder. The strength would further increase as the powder picked up oxygen as a result of re-use resulting in an overall higher strength curve and a significantly lower cost of production.

(2) TABLE-US-00001 TABLE 1 Composition of Ti6Al4V alloy as defined in the ASTM B348 Grade 5 specification Ti6Al4V ASTM B348 Grade 5 Min Max Element wt % wt % Aluminum 5.5 6.75 Vanadium 3.5 4.5 Iron 0.4 Oxygen 0.2 Nitrogen 0.05 Carbon 0.08 Hydrogen 0.015 Other Elements, each 0.1 Other Elements, total 0.4 Titanium Balance

(3) TABLE-US-00002 TABLE 2 Composition of Ti6Al4V enhanced strength titanium alloy. Enhanced Strength Ti6Al4V Min Max Element wt % wt % Aluminum 6.3 6.7 Vanadium 4.2 4.5 Iron 0.25 0.4 Oxygen 0.1 0.13 Nitrogen 0.02 0.05 Carbon 0.04 0.08 Hydrogen 0.0125 Other Elements, each 0.1 Other Elements, total 0.4 Titanium Balance

(4) The following table lists the chemical analysis of starting bar stock formulated to produce enhanced strength Ti-6A1-4V powder.

(5) TABLE-US-00003 TABLE 3 Composition of Ti6Al4V enhanced strength titanium alloy starting bar stock. Element wt % Aluminum 6.44 Vanadium 4.28 Iron 0.20 Oxygen 0.09 Nitrogen 0.04 Carbon 0.05 Hydrogen 0.002 Yttrium <0.001 Titanium Balance

(6) The experimentally determined room temperature tensile properties of this starting stock are given in the following table with the required minimum properties for ASTM B348 Grade 5.

(7) TABLE-US-00004 TABLE 4 Room temperature properties of enhanced strength titanium alloy starting bar stock. Tensile 0.2% Yield Strength Strength Elongation Reduction ksi (MPa) ksi (MPa) % of Area % Enhanced 145 (1000) 131 (905) 16 44 Ti6Al4V ASTM B348 130 (896) min 120 (827) min 10 min 25 min Grade 5

(8) As indicated in Table 4, the room temperature tensile properties of the enhanced Ti-6A1-4V meets the property requirements of the ASTM B348 Grade 5 specification although the oxygen content is well below the typical oxygen content of Grade 5 product. Conversion of this starting stock to powder will result in a small increase in oxygen content which will increase strength further with essentially no detriment to ductility.

(9) While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.