WO2001071337A1

WO2001071337A1 - Method of detecting hard alpha inclusions in a titanium casting

Info

Publication number: WO2001071337A1
Application number: PCT/US2001/007808
Authority: WO
Inventors: George R. Strabel
Original assignee: Howmet Research Corporation
Priority date: 2000-03-16
Filing date: 2001-03-12
Publication date: 2001-09-27

Abstract

A nondestructive method for inspecting a net-shaped or near-net-shaped titanium base investment casting (12) by scanning a depth of the casting below an exterior surface (12 S) thereof with an ultrasonic wave formed by a phased array probe (20) to inspect for a randomly located, subsurface hard alpha inclusion particle, shell mold-originated inclusion particle and other crack-initiating inclusion particle present in the microstructure of the casting (12). The method is especially useful and beneficial with respect to detecting hard alpha inclusion particles in the microstructure of a fracture-critical region of a structural airframe titanium based investment casting.

Description

METHOD OF DETECTING HARD ALPHA INCLUSIONS IN A TITANIUM CASTING FIELD OF THE INVENTION

The present invention relates to a method of detecting fatigue crack-initiating inclusion particles in a metallic casting, especially hard alpha inclusion particles in a titanium base structural airframe investment cast componen . BACKGROUND OF THE INVENTION

Net-shape or near-net-shape investment castings of titanium and titanium alloys are being considered for fracture-critical structural airframe applications to save weight and cost over forged and machined structural airframe components. For example, wing-to-body and aileron structural castings are being considered for use on an certain fighter aircraft. However, in investment casting of such airframe castings, there have been observed interstitial-containing, so-called hard alpha inclusion particles present at one or more random locations in the microstructure of the investment¹ casting . For example, relatively brittle oxygen-, nitrogen-, and/or carbon-containing alpha titanium inclusion particles have been observed in titanium alloy airframe castings and are thought to be sites that may adversely affect the fatigue life of investment cast airframe components in service.

Titanium based investment castings typically are made using the well known lost wax process where an injection molded wax pattern, or assembly of injection molded wax patterns, of the component to be cast are formed. The pattern of the component to be cast then is repeatedly dipped in ceramic slurry, drained of excess slurry, and stuccoed with relatively coarser ceramic stucco or sand to build up a shell mold of desired thickness on the pattern. Then, the pattern is selectively removed from the shell mold by thermal or chemical pattern removal techniques, leaving the green shell mold with a mold cavity having a shape corresponding to that of the component to be cast. The green shell mold is heated (fired) at elevated temperature to develop mold strength for casting. The fired ceramic shell mold is preheated to an elevated casting temperature and positioned in a vacuum casting furnace where an electrode ingot of titanium or titanium alloy is melted into a water cooled copper induction skull crucible and then poured into the preheated shell mold where the molten titanium or alloy is solidified. The shell mold then is removed from the cast titanium based component by mechanical and/or chemical techniques, cleaned, hot isostatically pressed, heat treated and inspected for dimensional tolerance and defects by fluorescent penetrant inspection and X-ray inspection. The casting can be chemically treated or etched in conventional manner to remove any alpha case present at the outer surface of the casting. The cast component may be reworked by TIG (tungsten inert gas) welding to repair any cast defects detected by inspections .

The interstitial-containing hard alpha titanium inclusion particles can originate from exogenous contamination of melt stock sources (e.g. ingot melt stock melted in the vacuum casting furnace) and numerous foundry sources of contamination. For example, some twenty-eight different potential sources of contamination leading to hard alpha inclusions have been identified by Shamblen et al . "Titanium Base Alloys Clean Melt Process Development", Proc . 1989 Vacuum Metallurgy Conf . , American Vacuum Society, Pittsburgh, PA, May 8-10, 1989, pp. 3- 11. The most frequent sources are thought to be bulk revert material comprising alloy scrap, flame-cut revert material, contamination from electrode-to-stub weld splatter exposed to air, and inadequate cleaning of the vacuum casting chamber prior to each melting and casting operation. Air leakage into titanium reduction and melting equipment also has been noted as a source of oxygen and nitrogen. More particularly, the torch cutting in air of the titanium skull solidified in the water cooled copper induction skull crucible to remove the skull prior to the next melting/casting operation, torch cutting of gating from the castings, and torch cutting within the vacuum casting chamber to clean the chamber involve exposing molten titanium and titanium alloy material to air such that oxygen and nitrogen can be dissolved in the material. Such interstitial- containing material may find its way into a shell mold during handling and casting operations. Also, condensate and/or splashed titanium material produced during casting in the casting furnace and exposed to air while hot prior to casting of the next shell mold can be a source of contamination leading to hard alpha inclusions if they dislodge and fall into the melt cast in the next shell mold. Further, air grinding operations on castings can result in titanium debris that can find its way into the shell mold or melt cast therein in the foundry environment .

Interstitial elements, such as O, N, and C, embrittle and stabilize hard alpha titanium inclusions. Thus, hard alpha inclusions present in a titanium melt from a contamination source are slow to dissolve in the titanium melt and thus more likely to survive through a melting and casting operation and thus be present in a solidified titanium or titanium alloy investment casting.

Oxygen-, nitrogen- and/or carbon-containing hard alpha inclusion particles present in the alpha/beta duplex microstructure of investment cast Ti-6A1-4V component become bonded in the microstructure and interact with the titanium based microstructure, typically by diffusion of the interstitial elements during cooling from the casting temperature and during subsequent hot isostatic pressing and heat treatment to form an interstitial-rich alpha-titanium diffusion zone about the inclusion particle. This alpha-titanium diffusion zone so formed provides a relatively brittle interstitial-containing region about the original brittle hard alpha titanium inclusion particle. Such hard alpha inclusion particles and the brittle interstitial-rich zone thereabout are also referred to as a hard alpha inclusions.

Ceramic inclusion particles originating from the shell mold are known to react with the titanium based melt to form relatively brittle interstitial-enriched alpha titanium and one or more relatively brittle titanium intermetallic compounds about the shell mold-originated inclusion. U.S. Patent 5 975 188 describes a ceramic shell mold that includes an erbium-bearing mold facecoat to enable better detection of any randomly located subsurface inclusions originated from shell mold spallation during investment casting of titanium based structural airframe components .

There has been considerable work in detecting inclusions in forged titanium base billets to detect low density hard alpha inclusions. Forged billet inspection is made easier by virtue of regular billet geometry as well as the hot work imparted to the billet. Hot working of billets results in microstructural refinement that reduces noise associated with large prior beta grain facets in the as-cast billet during inspection and also fractures hard alpha inclusion particles such that the fractured particles attenuate and reflect ultrasonic waves more effectively, leading to improved detection.

However, inspection for hard alpha inclusion particles in net- shape and near-net-shape titanium base investment castings is complicated by the more complex geometries involved as well as the lack of hot working of the casting that leaves thermal stress cracks and internal porosity therein that complicate detection of hard alpha particles in the cast microstructure. There is needed an improved method of detecting hard alpha inclusion particles in investment cast titanium base structural airframe components .

An object of the present invention is to satisfy this need.

Another object of the present invention is to provide a nondestructive inspection method for inspecting for one or more randomly located interstitial-containing hard alpha inclusion particles, shell mold-originated inclusion particles and other crack-initiating inclusion particles present in the microstructure of a metallic cast component, especially in the microstructure of a structural airframe titanium based investment cast component . SUMMARY OF THE INVENTION

The present invention provides a nondestructive method for inspecting a metallic cast component by inspecting a region of the component below an exterior surface thereof with an ultrasonic beam formed or generated by a phased array probe to inspect for a randomly located, subsurface hard alpha inclusion particle, shell mold-originated inclusion particle and other inclusion particle that may be present in the microstructure of the cast component. The method is especially useful and beneficial with respect to inspecting for hard alpha inclusion particles in the microstructure of a fracture-critical region of a structural airframe titanium or titanium alloy investment cast component where the component can have an illustrative cross- sectional thickness of about 0.2 inch to about 4 inches for purposes of illustration and not limitation.

An illustrative embodiment of the present invention involves scanning a fracture-critical structural airframe titanium or titanium alloy net-shape or near-net-shape investment cast component using a phased array probe having a plurality of ultrasonic elements pulsed to direct the ultrasonic beam into the component below an exterior surface thereof to interrogate for the presence of a hard alpha inclusion particles and other crack- initiating inclusion particles in the cast microstructure. In this embodiment, the phased array system typically is operated in a dynamic beam mode to provide dynamic depth-focusing and sectorial scanning of the cast component. The inspection probe can be moved along the investment cast component for inspection, although the invention can be practiced with relative movement between the investment cast component and the probe or with the probe stationary.

The above objects and advantages of the present invention will become more readily apparent from the following detailed description. DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a titanium based wing-to-body investment cast component and an inspection probe and associated apparatus for practicing an illustrative embodiment of the invention .

Figure 1A is an enlarged perspective view of a clevis region of the wing-to-body investment cast component of Figure 1.

Figure 2 is an elevational view of the inspection probe having two dimensional array of thirty two ultrasonic transducers.

Figure 3A is an elevational view of an NDI specimen comprising bonded first cast titanium based plate and a second cast titanium based plate for inspection using a method embodiment of the invention .

Figure 3B is an elevational view of the surface of the first cast titanium based plate of the NDI specimen of Figure 3A.

Figure 3C is a partial sectional view of a recess in the surface of the first cast titanium based plate.

Figure 4 is an exploded view of an NDI specimen having randomly placed defects. DESCRIPTION OF THE INVENTION

The present invention provides a nondestructive method for inspecting a metallic cast component by scanning the cast component below an exterior surface thereof with an ultrasonic wave or beam formed by phased array focusing to interrogate for one or more subsurface inclusion particles present in the microstructure of the cast microstructure . The method of the invention is especially useful and beneficial with respect to detecting hard alpha and shell mold-originated inclusion particles in the microstructure of a structural airframe titanium based investment casting where the casting can have a cross- sectional thickness of about 0.2 inch to 4 inches. The structural airframe investment casting can comprise titanium and its alloys, such as for example, Ti metal, Ti-6A1-4V alloy, Ti-6Al-2Sn-4Zr- 2Mo, and other titanium based alloys. By hard alpha inclusion particle is meant a localized particulate region, such as for example an inclusion particle, in the microstructure of the cast component where the particulate region comprises alpha titanium containing one or more interstitial elements selected from the group consisting of 0, N and C. The particulate region typically is hard and brittle relative to the surrounding microstructure of the component by virtue of the presence of one or more of the interstitial elements; namely, 0, N, and/or C. A diffusion zone enriched in one or more of these interstitial elements may be present about and encapsulate the hard alpha inclusion particle and will appear as a light etching halo in the microstructure about the hard alpha inclusion particle when etched with 100% ammonium bifluoride etchant . Such an interstitial-bearing hard alpha inclusion particle with or without the diffusion zone thereabout is referred to herein as a hard alpha inclusion particle .

A shell mold-originated inclusion particle typically comprises a ceramic shell mold fragment that has spalled from the mold facecoat or other mold region and become entrained or otherwise present in the molten titanium metal or alloy cast in the mold. A diffusion zone enriched in one or more of the above mentioned interstitial elements may be present about the shell mold- originated inclusion particle and will appear as a light etching halo in the microstructure about the shell mold-originated inclusion particle when etched with a 100% ammonium bifluoride etchant. Other defects and/or inclusions particles which may be present in the microstructure of a structural airframe titanium based investment casting include a lack of fusion (LOF) defect comprising an unbonded internal seam, porosity defect, high density inclusions, and ceramic type inclusions.

For purposes of illustration, the method of the invention is described below to inspect for inclusion particle (s) in the microstructure of a fatigue-critical region of a structural airframe titanium based investment cast component, which typically is not forged, swaged or otherwise mechanically worked to cause plastic deformation thereof subsequent to casting. The invention can be used to inspect a fatigue-critical region of such a structural airframe titanium based investment cast component in the as-cast condition (i.e. without further treatment) , in a hot isostatically pressed condition, in a heat treated condition, in the machined condition and any other condition. The cast component can be inspected after a conventional chemical etch to remove any alpha case present on an external surface of the cast component . The structural airframe investment cast component can have a varied cross- sectional thickness with a typical cross-sectional thickness in the range of about 0.2 inch to 4 inches for purposes of illustration and not limitation. Illustrative of such structural airframe investment cast components that can be inspected pursuant to the invention are wing-to-body cast components, aileron structural cast components, as well as other fracture- critical (e.g. fatigue-critical) structural airframe components. The invention can be used to inspect a variety of investment cast net -shape or near-net-shape stationary aircraft components and rotating aircraft and gas turbine engine components.

Referring to Figure 1, an illustrative embodiment of the present invention involves scanning a titanium based net-shape or near-net-shape investment cast component 10, shown as a wing- to-body component having a main body 11 to which an aircraft wing is attached and a plurality of fracture-critical clevis attachment regions 12, 14, 16, and 18. After inspection pursuant to the invention, the clevis attachment regions typically are bored or drilled in a direction perpendicular to the clevis walls 12a, 12b; 14a, 14b; 16a, 16b; and 18a, 18b in order to receive attachment pins by which the wing-to-body component 10 is fastened to a main fuselage frame (not shown) of an aircraft. Each clevis region includes a pair of clevis walls 12a, 12b; 14a, 14b; 16a; 16b; and 18a, 18b separated by a respective slot 12c, 14c, 16c, and 18c. The cast component 10 typically is inspected after subjecting the cast component to hot isostatic pressing with or without a subsequent heat treatment and after a conventional chemical etching treatment to remove any alpha case formed on exterior surfaces of the hot isostatically pressed/heat treated component, although the invention is not limited in this regard.

In an illustrative embodiment of the invention, the clevis walls 12a, 12b; 14a, 14b; 16a, 16b; and 18a, 18b are considered fracture- critical regions that are inspected pursuant to the invention using an ultrasonic wave established by phased array focusing using a phased array probe to interrogate for the presence of any randomly located, subsurface hard alpha inclusion particle, shell mold-originated inclusion particle and other crack-initiating inclusion particle that may be present in the microstructure of the clevis walls.

In an illustrative embodiment of the invention, Figure 1A, clevis wall 12a is inspected by moving an inspection probe 20 on the outer surface 12s of clevis wall 12a along a serpentine path P (or any other configuration path) from the closed end of the slot 12c toward the open end of slot 12c at the free end of the clevis wall 12a, or vice versa, to interrogate from surface 12s to surface 12i. The probe 20 includes an array of multiple piezoelectric transducers 22 that are electrically pulsed to form an ultrasonic beam by phased array focusing and is moved relative to the cast component 10 along path P to direct the phased array focused ultrasonic beam (or wave) into the cast component 10 below exterior surface 12s to inner surface 12i to interrogate for the presence of a crack-initiating inclusion particle in the casting microstructure. The cast component 10 can be immersed in a water tank (not shown) with the probe 20 moved along the exterior clevis surface 12s thereof. Alternately, the probe 20 can be placed and moved on the clevis surface 12s of the cast component 10 outside of a tank with the surface 12s wetted with a suitable acoustical coupling fluid, such as water or grease, between the clevis surface 12s and the probe 20.

The other clevis walls 12b; 14a, 14b; 16a, 16b; and 18a, 18b are inspected in the same manner as described above for clevis wall 12a. Moreover, the main body 11 of the wing-to-body cast component 10 can also be inspected as desired and as described above pursuant to the invention.

The phased array inspection probe 20 can comprise a commercially available phased array ultrasonic inspection probe for use with a commercially available phased array focusing ultrasonic inspection system. For example, the phased array probe 20 can comprise a model 10L32E9.92-7 probe available from R/D Tech, Quebec, Canada, having a two-dimensional array of thirty- two (32) ultrasonic transducers or elements 22 as shown in Figure 2 with the elements 22 pulsed at different times to provide dynamic ultrasonic beam control. The invention envisions using other phased array probes having linear, annular or other arrays of multiple transducers or elements as manufactured by R/D Tech, Quebec, Canada.

The phased array probe 20 is operable with the Phased Array Scanning computer control system also available from R/D Tech, Quebec, Canada. The model 10L32E9.92-7 probe is operated at 10 MHz with a typical bandwidth of 60% and typical wave duration of 300 ns (nanoseconds) . A suitable acoustical coupling or adaptation fluid, such as water or grease, can be used between the probe and the clevis surface of the cast component to be inspected if the component is inspected outside of a water tank. The above model 10L32E9.92-7 probe is used with and connected via a flexible electrical connector C to the above Phased Array Scanning computer control system. The system generates an ultrasonic beam by pulsing transducers or elements 22 at different times. By precisely controlling the time delays between the probe elements, beams of various angles, focal distance, and focal spot size can be produced. The above system preferably is operated to provide the system manufacturer's dynamic depth- focusing mode of operation where the focus of the beam changes as a function of acquisition time on reception suitable for long sound paths and small beam divergence preferably with sectorial scanning to scan successive sectors or zones of the cast component as the probe is moved. If used, sectorial scanning is controlled by a control setting on the computer control unit 31, shown schematically in Figure 2, of the Phased Array Scanning computer control system to adjust the degrees of beam scanning within a selected range (e.g. plus or minus a selected degree range, such as for example, plus or minus 20 degrees, relative to a probe axis perpendicular to the clevis outer surface; e.g. clevis surface 12s) . The dynamic depth- focusing on reception of the beam also can be controlled by the Phased Array Scanning computer control system in dependence on the thickness of the cast component being inspected. Dynamic depth- focusing involves a beamforming technique available from R/D Tech, Quebec, Canada, as variable delay laws as a function of time where a single focal law is used for beam transmission and many subsequent delay laws are used for reception by the probe element array. Dynamic depth- focusing is advantageous to extend the depth-of-field inspected, reduce the beam spread, and increase the overall signal-to-noise ratio. The dynamic-depth focusing is controlled in dependence on the thickness range of the cast component to be inspected pursuant to the manufacturer's system software instructions for the above Phased Array Scanning computer control system available from R/D Tech, Quebec, Canada. The Phased Array Scanning computer control system also is operated with a time correction factor that depends on the depth of beam focus used. The time correction factor is a calibration factor and is input into the manufacturers ' system software provided with the above Phased Array Scanning computer control system based on calibration tests where a calibration specimen having a defect of known depth is scanned. The time correction factor is determined and input to the system software pursuant to the manufacturer's system software instructions for the Phased Array Scanning computer control system. A personal or other computer 32 can be interfaced with the control unit 31 to display a computer reconstructed image of the scanned component on the video screen of the computer .

The following examples are offered for purposes of illustrating the invention and not limiting it:

NDI (nondestructive test inspection) specimens were made of first and second bonded investment cast Ti-6Al-4V titanium alloy plates 30, 40 shown in Figure 3A, 3B, and 3C cut by wire EDM (electrical discharge machining) from an investment cast block simulating a titanium alloy cast structure of a component. The cast block had been conventionally hot isostatically pressed to close internal porosity. The titanium alloy is well known and comprises, nominally, 6 weight % Al , 4 weight % V and balance essentially Ti . The wire EDM'ed surfaces were chemically milled to remove 0.001 to 0.002 inch of any recast layer from EDM'ing. Prior to bonding of the plates 30, 40 together, a surface 30a of the relatively thicker plate 30 was drilled to form holes of different diameters and constant depth of about 0.006 inch, Figures 3A and 3C. The holes were arranged on the plate surface as shown in Figure 3B with about a 1 inch spacing between holes and with the different diameters shown. One row of holes had diameters (d) of dl , d2 , d3 , d4 , d5 , d6 , and d7 of 0.016 inch, 0.031 inch, 0.047 inch, 0.063 inch, 0.094 inch, 0.156 inch and 0.25 inch, respectively, and were filled with shell mold material, such as yttria mold facecoat particulate material, simulating a shell mold-originated inclusion.

A second row of holes had diameters d8 , d9 , dlO, dll, dl2, and dl3 of 0.016 inch, 0.031 inch, 0.047 inch, 0.078 inch, 0.125 inch, and 0.188 inch, respectively, and were filled with tungsten particulate material, simulating tungsten weld repair contamination .

NDI specimens were made by electron beam welding the outer periphery of the joint between plates 30, 40 and then bonding first and second plates 30, 40 with an aggregate specimen thickness t, Figure 3A, of 0.25 inch, 0.50 inch, 1.00 inch, 1.5 inches, and 2.00 inches with the first plate 30 comprising 2/3 of the specimen thickness t, Figure 3A, and the second plate comprising 1/3 of the specimen thickness. The plates 30, 40 were bonded together by placing the drilled surface 30a and facing surface of plate 40 in contact and electron beam (EB) welding the outer periphery of the joint between the plates under vacuum to provide a gas tight seal and then hot isostatically pressing (HIP'ing) the assembled plates 30, 40 at 1650 degrees F for 2 hours in an argon atmosphere at 15 ksi pressure. The HIP'ing treatment metallurgically bonded the mating plate surfaces together and eliminated any joint or interface between the plates. The bonded plate specimens then were subjected to a beta solution heat treatment and overaging heat treatment (e.g. 1880 degrees F for 1/2 hour, gas fan cool and 1550 degrees F for 2 hours, gas fan cool) followed by a second chemical milling treatment with the EB weld masked to remove about 0.010 inch of surface from the specimen to remove any alpha phase from the heat treatment. The EB weld was then ground flush. The plate specimens exhibited a typical two phase, alpha phase plus beta phase, duplex microstructure.

The model 10L32E9.92-7 probe available from R/D Tech, Quebec, Canada, having a two-dimensional array of thirty-two (32^') ultrasonic transducers 22 was used to inspect the bonded plates 30, 40 described above. The probe was placed on the major surface 30s of the plate 30 and then also on the major surface 40s of plate 40 to interrogate for inclusions. The depth of focus of the above Phased Array Scanning computer control system was set to the range of specimen thicknesses being scanned and the time correction factor was programmed into the system software based on calibration using specimens with known depth of focus of the specimens being scanned. The beam sectorial scanning was set at plus or minus 20 degrees relative to a probe axis perpendicular to the major surface 30s and 40s of plate 30 and 40. The probe was manually moved in a continuous linear motion along the surface of the plate specimen along each line of simulated inclusions/contamination during inspection. Water was used as the coupling fluid between the probe and the plate. The shell mold inclusion particles and tungsten particles in the plate specimen were detected consistently by the phased array ultrasonic scanning technique describe above .

A similar inspection of an NDI investment cast Ti-6A1-4V plate specimen having randomly located hard alpha inclusion particles and ceramic inclusion particles was conducted. Referring to Figure 4, the specimen comprised first and second investment cast Ti-6A1-4V titanium alloy plates 50, 60 wire EDM'ed from an investment cast block as described above for the above example . Plate 50 had approximate dimensions length 1 = 6 inches, width w = 4 inches, and thickness t = 1.3 inches. Plate 60 had approximate dimensions of length 1 = 6 inches, width w = 4 inches, and thickness t = 0.7 inch. Prior to bonding of the plates 50, 60 together, the wire EDM'ed surfaces were chemically milled as described above and surface 60a of the plate 60 was drilled to form holes each of a diameter d of 0.25 inch and depth of 0.15 inch to simulate random defects. The holes were arranged on the plate surface in random locations as shown in Figure 4. Some holes designated E were left empty, some holes designated S received an alpha titanium slag particle (simulating a hard alpha particle) of approximate 0.125 to 0.150 inch diameter produced by torch cutting of Ti-6A1-4V in air. Some holes designated C received a ceramic material particle (e.g. erbia mold facecoat material particle) of approximate 0.125 to 0.150 inch diameter simulating a shell mold inclusion particle.

The NDI plate specimens were electron beam welded together at their outer periphery and hot isostatically pressed (HIP'ed) at 1650 degrees F for 2 hours in an argon atmosphere at 15 ksi pressure and then beta solution heat treated and overage heat treated followed by a second chemical milling treatment as described above. The plate specimen exhibited a typical two phase, alpha phase plus beta phase) duplex microstructure.

The above model 10L32E9.92-7 probe available from R/D Tech, Quebec, Canada, having a two-dimensional array of thirty-two ultrasonic transducers 22 was used to inspect the NDI plate specimen described above. The probe was placed on the major surface 50s of the plate 50 and then also on major surface 60s of plate 60 for interrogation. The depth of focus of the above Phased Array Scanning computer control system was set to the specimen thicknesses being scanned and the time correction factor was programmed into the system software based on calibration using specimens with known depth of focus of the specimens being scanned. The beam sectorial scanning was set at plus or minus 20 degrees relative to a probe axis perpendicular to the major surface 50s and 60s of plate 50 and 60. The probe was manually moved continuously along the surface of the plate specimen along a serpentine path during inspection. Water was used as the coupling fluid between the probe and the plate. The hard alpha inclusion particles and shell mold inclusion particles were detected in the plate specimen.

Although the invention has been described hereabove with respect to certain embodiments and aspects, those skilled in the art will appreciate that the invention is not limited to the particular embodiments and aspects described herein. Various changes and modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims .

Claims

CLAIMS1 Claim:

1. A nondestructive method for inspecting a metallic cast component, comprising inspecting a region of the component below an exterior surface thereof with an ultrasonic beam formed by a phased array probe to inspect for a randomly located, subsurface inclusion particle in said casting.

2. The method of claim 1 wherein said beam sectorially scans said component .

3. The method of claim 1 including dynamic depth focusing of the beam.

4. The method of claim 2 wherein said beam is generated by an array comprising a plurality of pulsed ultrasonic elements.

5. A nondestructive method for inspecting a cast component comprising titanium, comprising inspecting a region of the component below an exterior surface thereof with an ultrasonic beam formed by a phased array probe to inspect for a randomly located, subsurface inclusion particle in said casting.

6. The method of claim 5 including inspecting for a hard alpha inclusion particle.

7. The method of claim 5 wherein said beam sectorially scans said component .

8. The method of claim 5 including dynamic depth focusing of the beam.

9. A nondestructive method for inspecting a structural airframe investment cast component comprising titanium, comprising inspecting a region of the component below an exterior surface thereof with an ultrasonic beam formed by a phased array probe to inspect for a randomly located, subsurface inclusion particle in said casting.

10. The method of claim 9 including inspecting for a hard alpha inclusion particle.

11. The method of claim 9 wherein said beam sectorially scans said component .

12. The method of claim 9 including dynamic depth focusing of the beam.

13. The method of claim 9 including moving said probe relative to said component .

14. The method of claim 9 wherein said beam is generated by an array comprising a plurality of pulsed ultrasonic elements.

15. The method of claim 9 wherein said depth of said component having a thickness in the range of about 0.2 inch to about 4 inches is scanned.

16. A nondestructive method for inspecting a structural airframe investment cast component comprising titanium, comprising inspecting a region of the component with an ultrasonic beam formed by a phased array probe to inspect for a randomly located, subsurface inclusion particle in said component.

17. The method of claim 16 including inspecting for a hard alpha inclusion particle.