EP0049207B1 - Process for machining the surface of a nickel base superalloy workpiece - Google Patents

Process for machining the surface of a nickel base superalloy workpiece Download PDF

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Publication number
EP0049207B1
EP0049207B1 EP81630055A EP81630055A EP0049207B1 EP 0049207 B1 EP0049207 B1 EP 0049207B1 EP 81630055 A EP81630055 A EP 81630055A EP 81630055 A EP81630055 A EP 81630055A EP 0049207 B1 EP0049207 B1 EP 0049207B1
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EP
European Patent Office
Prior art keywords
workpiece
process according
etchant
recast layer
machining
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP81630055A
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German (de)
English (en)
French (fr)
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EP0049207A1 (en
Inventor
Robert Eugene Fishter
Henry Lada
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RTX Corp
Original Assignee
United Technologies Corp
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Filing date
Publication date
Application filed by United Technologies Corp filed Critical United Technologies Corp
Publication of EP0049207A1 publication Critical patent/EP0049207A1/en
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Publication of EP0049207B1 publication Critical patent/EP0049207B1/en
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
    • C23F1/14—Aqueous compositions
    • C23F1/16—Acidic compositions
    • C23F1/28—Acidic compositions for etching iron group metals

Definitions

  • the present invention concerns a process for machining the surface of a nickel-base superalloy workpiece comprising removing workpiece material using a thermal-effect process which causes melting and vaporization of metal, thereby leaving on the workpiece surface a recast layer.
  • the machining of the superalloy is carried out by chemical milling in combination with thermal effect metal removal processes, such as those utilizing electric discharge and lasers.
  • a beam is impinged in concentrated form on a cast airfoil workpiece surface until it penetrates through.
  • metal is melted and vaporized by the intense beam energy, creating the hole.
  • the intensity of these processes is such that molten and vaporized metal is expelled from the hole being created, this effect being augmented by the use of a volatilizable backer material at the workpiece exit surface.
  • EDM electric discharge machining
  • EDM surfaces are usually characterized by a certain roughness caused by the erratic nature of the spark discharge and in many instances it is desired to have a smoother surface than is typically producible.
  • a general secondary machining operation such as grinding is used to smooth an EDM surface the good accuracy from the EDM process can easily be lost, or costs will be increased.
  • the process of the invention is characterized in contacting the surface from which material is removed with an etchant comprised by volume percent of 40-60 of 69-71% concentrated HN0 3 , 5-20 of 36.5-38% HCI, balance H 2 0, at least 0.016 moles/liter CuS0 4 and 0.008-0.025 moles/liter FeCl 3 , until the recast layer has been chemically dissolved without substantial removal of the workpiece surface material.
  • the etchant consists of 50 vol.% of 69-71% concentrated HN0 3 , 10 vol.% of 36.5-38% HCI, balance water with 1.3 g/I FeCI 3 and 2.6 g/I CuS0 4 .
  • the FeCI 3 improves removal rate but tends to cause unwanted pitting and intergranular attack. These tendencies are inhibited by the addition of C U S0 4 ; preferably the molar ratio of CuS0 4 to FeCI 3 is 2:1.
  • the beneficial combination of FeCI 3 and CuS0 4 is usable in other etchants.
  • the etchant has a self-limiting feature that is very unique. Only the recast layer is removed and the removal of metal which is not recast is minimal. Gas is evolved during removal (preferably done at 40-80°C) and the cessation of evolution may be used as an indication of the completion of the chemical milling process.
  • the invention provides a rapid way for removing material from a superalloy since thermal effect processes are exceedingly fast and the chemical milling is very selective and also rapid. Machined superalloy surfaces with surfaces free from adverse metallurgical features are thereby provided.
  • the invention is described hereafter in application to the nickel-base superalloy MAR M-200 + Hf, a nickel-base alloy having the composition by weight percent of 10 Co, 9 Cr, 2 Ti, 5 Al, 12 W, 1 Nb, 2 Hf, 0.15 C, 0.015 B, 0.05 Zr, balance Ni. Limited experiment indicates that the process will be useful for other nickel alloys, especially the superalloys such as IN-100, IN-718 and Astroloy.
  • the invention was used to produce both holes of improved quality in airfoil walls, and contoured surfaces on superalloys.
  • the hole drilling will be described first.
  • About 10 holes of 0.7 to 1.3 mm diameter were drilled in the as-cast surface of a hollow airfoil wall workpiece having a thickness of about 2.5 mm; the holes were at different inclinations to the surface and thus ranged in length between 2.5 and 5 mm.
  • a neodymium laser generated pulse radiation at 1.06 micron wavelength was applied to the workpiece entrance surface at an intensity of about 10 7 watts/cm 2 , with a pulse duration of about 660 microseconds and rate in the range 0.3 to 1 pulses/second.
  • Figure 1 (a) is a view of the entrance of the drilled hole on the surface 16 of a workpiece.
  • the beam has impinged on the surface so that the hole slants downward toward the left of the photograph.
  • the recast layer 10 Around the entrance of the hole can be seen the recast layer 10, containing a prominent crack 12 as well as other cracks.
  • Some other recast layer molten material 14 is on the surface surrounding the hole as well.
  • Figure 2(a) shows a portion of a longitudinal section through the same hole.
  • the specimen has been etched to reveal microstructure and the recast layer 10 which is light colored and featureless compared to the more characteristic cast morphology of the base metal 18 which is more removed from the hole.
  • the recast layer was non-uniform and varied in thickness from about 0.08 to 0.8 mm.
  • Figures 1 (b) and 2(b) are analogous views to Figures 1 (a) and 2(a), showing the workpiece after chemical milling which is described in more detail below.
  • EDM techniques are used to produce a pattern of grooves varying in depth from 2.4 to 2.9 mm and in width from 1.5 to 1.8 mm.
  • a rectangular parallel-piped test piece with an entirely EDM surface of about 1.61 sq. cm on one face was produced.
  • the EDM conditions were nominally: 80 volts DC; 3 amps; a pulse frequency of 3 kilocycles; a capacitance of 1 microfarad; using a carbon electrode with a mineral seal dielectric fluid (Exxon Mentor No. 28, Exxon Corp., Houston, Texas) at 27°C.
  • the foregoing conditions are characteristic of those used for a light roughing mode of operation.
  • a suitably shaped electrode is prepared, and the EDM parameters adjusted according to the area and other considerations in a manner familiar to those with skill in EDM.
  • the EDM produced a surface finish (as measured by a surface profilometer) of about 2.0-3.0 root mean square (RMS) mm.
  • RMS root mean square
  • the surface condition of a portion of the EDM surface is shown in planar view in Figure 3(a) and in cross section in Figure 4(a). In the latter figure the lighter recast layer 20 is evident in contrast to the unaffected base metal 22, similarly to the appearance of the laser drilled holes.
  • the recast layer varied in thicknes from 0.08 to 0.8 mm.
  • thermal effect processes Removal of material by either laser or EDM are designated herein as "thermal effect processes”. By this we mean they are processes in which metal is removed by heating above its melting point and wherein there is a residual recast layer on the workpiece surface. Thus we embrace in the scope of our. invention other thermal effect processes including but not limited to those mentioned in the Background.
  • the workpiece having the laser drilled holes was immersed in the etchant at 77°C; after initially observed gas evolution ceased, the workpiece was removed from the etchant and examined. As shown in Figures 1 (b) and 2(b) the recast layer was completely removed from the drilled holes. There was some small degree of general attack on the non-recast areas of the workpiece as evidenced by the Figures and examination showed the 6.55 gm workpiece had lost only about 0.118 gm or 1.8% of its original weight. Thus, the substantial effect of the chemical milling was to only the recast layer, and more uniform, smooth, and crack-free holes were provided.
  • a very striking aspect of the invention is the self-limiting nature of the chemical milling portion of the process.
  • the evolution of gas (hydrogen) is evidence of substantial metal removal; thus when the gas evolution substantially ceases the quantity of metal being dissolved per unit time is substantially reduced.
  • the process is self-limiting and the near-cessation of gas evolution gives a signal that the removal of the undesired recast material is complete.
  • FeCI 3 should not be added beyond the indicated range, regardless of the amount of CuSO 4 , because the inhibiting action of CuSO 4 will not be sufficient. On the other hand, the amount of C U S0 4 may be increased beyond the indicated range since it is benign. We believe that the combination of FeCl 3 and CuSO 4 to be novel and significant in chemical removal of superalloys.
  • the moderately elevated temperature we used is desirable to increase the rate of reaction; apart from our nominal best temperature of 66°C, the process is believed operable between 40-80°C, and we prefer to operate in the range of 60-70°C.
  • Our invention combines laser or EDM with uniquely selective chemical milling.
  • our invention combines a thermal effect process with chemical milling using a specialized etchant. In its best use it provides precision machining and quality of surface condition in nickel alloys, but it will be applicable to other nickel alloy materials processing using a thermal effect process where the recast layer is undesirable.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • ing And Chemical Polishing (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
EP81630055A 1980-10-01 1981-09-23 Process for machining the surface of a nickel base superalloy workpiece Expired EP0049207B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US19266880A 1980-10-01 1980-10-01
US192668 1994-02-07

Publications (2)

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EP0049207A1 EP0049207A1 (en) 1982-04-07
EP0049207B1 true EP0049207B1 (en) 1984-09-12

Family

ID=22710579

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EP81630055A Expired EP0049207B1 (en) 1980-10-01 1981-09-23 Process for machining the surface of a nickel base superalloy workpiece

Country Status (10)

Country Link
EP (1) EP0049207B1 (es)
JP (1) JPS5824505B2 (es)
AU (1) AU544833B2 (es)
BR (1) BR8106057A (es)
CA (1) CA1165670A (es)
DE (1) DE3166048D1 (es)
DK (1) DK395481A (es)
ES (1) ES505893A0 (es)
IL (1) IL63859A (es)
NO (1) NO154759C (es)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108385108A (zh) * 2018-04-19 2018-08-10 东北大学 一种单晶高温合金精铸件化铣膏及其制备方法和应用

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339282A (en) * 1981-06-03 1982-07-13 United Technologies Corporation Method and composition for removing aluminide coatings from nickel superalloys
CN104020033A (zh) * 2014-05-28 2014-09-03 天津诚信达金属检测技术有限公司 一种常温9Cr-1Mo类钢晶界显示腐蚀剂
CN115386879B (zh) * 2022-08-15 2023-11-28 武汉钢铁有限公司 一种超低碳硅钢用腐蚀剂及腐蚀方法
FR3144931A1 (fr) * 2023-01-16 2024-07-19 Safran Procede d’usinage d’un trou de forme dans une piece

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3467599A (en) * 1966-08-08 1969-09-16 Philco Ford Corp Etching solution
GB1353960A (en) * 1971-09-21 1974-05-22 Rolls Royce Method of etching a partially masked surface
ES427394A1 (es) * 1973-06-18 1977-02-01 Oxy Metal Industries Corp Mejoras introducidas en un metodo de decapado de depositos de niquel acumulados en los dispositivos de metalizado y si-milares.

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108385108A (zh) * 2018-04-19 2018-08-10 东北大学 一种单晶高温合金精铸件化铣膏及其制备方法和应用
CN108385108B (zh) * 2018-04-19 2019-06-11 东北大学 一种单晶高温合金精铸件化铣膏及其制备方法和应用

Also Published As

Publication number Publication date
JPS5824505B2 (ja) 1983-05-21
IL63859A0 (en) 1981-12-31
AU544833B2 (en) 1985-06-13
AU7562281A (en) 1982-04-08
ES8205877A1 (es) 1982-06-16
IL63859A (en) 1984-05-31
DK395481A (da) 1982-04-02
JPS5789484A (en) 1982-06-03
NO154759C (no) 1986-12-17
BR8106057A (pt) 1982-06-08
NO154759B (no) 1986-09-08
ES505893A0 (es) 1982-06-16
CA1165670A (en) 1984-04-17
DE3166048D1 (en) 1984-10-18
EP0049207A1 (en) 1982-04-07
NO813191L (no) 1982-04-02

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