Aircraft landing gear struts coated with a zinc-nickel alloy

Patent metadata

Field	Value
Publication number	US-2017001717-A1
Application number	US-201615198156-A
Country	US
Kind code	A1
Filing date	Jun 30, 2016
Priority date	Jul 3, 2015
Publication date	Jan 5, 2017
Grant date	—

Abstract

Aircraft landing gear strut ( 1 ) comprising a main part ( 1 a ) extending along a main axis (X-X) of the strut and comprising an axle shaft ( 1 b ) extending in a plane (P) perpendicular to the main shaft ( 1 a ) of the strut, this axle shaft ( 1 b ) being designed to support at least one landing gear wheel ( 2 a, 2 b ) equipped with brakes ( 3 a, 3 b ) for braking the wheel, said axle shaft ( 1 b ) being made of steel.
The axle shaft ( 1 b ) bears at least one layer of zinc-nickel alloy coating (C), this zinc-nickel alloy comprising, as a mass percent of the alloy, between 12% and 18% of nickel, at most 0.5% of elements other than nickel and zinc, the rest being zinc.

First claim

1 .- 13 . (canceled)

14 . An aircraft landing gear strut ( 1 ) comprising:
a main part (la) extending along a main axis (X X) of the strut and comprising an axle shaft ( 1 b ) extending in a plane (P) perpendicular to the main shaft (la) of the strut, the axle shaft ( 1 b ) being designed to support at least one landing gear wheel ( 2 a , 2 b ) equipped with brakes ( 3 a , 3 b ) for braking the wheel, said axle shaft ( 1 b ) being made of steel, wherein the axle shaft ( 1 b ) has at least one layer of zinc nickel alloy coating (C), the zinc nickel alloy comprising, as a mass percent of the alloy, between 12% and 18% of nickel, at most 0.5% of elements other than nickel and zinc, the rest being zinc, wherein the axle shaft ( 1 b ) comprises at least one bearing seat ( 5 a , 5 b ) designed to accept at least one wheel bearing ring, each said at least one bearing seat ( 5 a , 5 b ) being formed by an annular layer of chrome formed on an external surface made of steel of the axle shaft ( 1 b ), the at least one layer of zinc nickel alloy coating extending at least over all the steel surfaces of the axle shaft that are situated outside of the said at least one bearing seat made of chrome ( 5 a , 5 b ), and wherein each at least one bearing seat ( 5 a , 5 b ) made of chrome extends between two chrome annular edges specific to it, the at least one layer of zinc nickel alloy coating extending over the annular edges made of chrome of each at least one bearing seat.

15 . The aircraft landing gear strut according to claim 14 , in which the said at least one layer (C) of zinc nickel alloy coating extends exclusively over external surfaces of the axle shaft which are chosen to be kept at a temperature of below 300° C. when the strut is used for performing a normal aircraft braking cycle.

16 . The aircraft landing gear strut according to claim 14 , in which the axle shaft ( 1 b ) extends through a bore ( 6 ) that passes through the main part of the landing gear strut, this axle shaft being tightly fitted into this bore ( 6 ), and a continuous annular portion of the layer of zinc nickel alloy coating (C) borne by the axle shaft ( 1 b ) forms an interface between the internal annular surface of the said bore ( 6 ) and a longitudinal portion of the axle shaft which extends into the bore ( 6 ).

17 . The aircraft landing gear strut according to claim 16 , in which the said internal annular surface of the bore bears an annular layer internal to the bore ( 6 ), this annular layer internal to the bore ( 6 ) being made of the same zinc nickel alloy.

18 . The aircraft landing gear strut according to claim 14 , in which the main strut and the axle shaft are formed as a single piece.

19 . The aircraft landing gear strut according to claim 14 , in which the zinc nickel alloy contains, as a mass percentage of the alloy, between 12% and 16% nickel.

20 . An aircraft landing gear comprising:
at least one landing gear strut ( 1 ) according to claim 14 ; at least one wheel ( 2 a , 2 b ) equipped with brakes ( 3 a , 3 b ) and supported by the axle ( 1 b ) of the said at least one landing gear strut ( 1 ).

21 . A method of manufacturing a landing gear strut ( 1 ) for an aircraft according to claim 14 , characterized in that it comprises:
a step of forming an axle shaft ( 1 b ) made of steel; followed by a step of applying the said at least one layer of zinc nickel alloy coating (C) to this steel axle shaft ( 1 b ), this application step being performed by immersing the said at least one axle shaft in an alkaline bath containing zinc and nickel in the form of ions and by applying an electrical potential between an electrode immersed in the bath and the steel axle shaft.

22 . The method of manufacturing a landing gear strut according to claim 21 , in which prior to the step of applying the coating to this steel axle shaft, a step of preparing a steel surface of the strut, comprising chemical or mechanical surface activation, is carried out.

23 . Method of manufacturing a landing gear strut according to claim 21 , in which, after the coating step, a passivation step is carried out which consists in immersing the portions of the strut that are coated with the layer of zinc nickel alloy coating in an acid solution.

24 . The method of manufacturing a landing gear strut according to claim 21 , further comprising a step of degassing any hydrogen potentially occluded in the steel, this degassing step involving placing the strut in a furnace for at least 12 hours, keeping the furnace at a temperature of 190° C. plus or minus 14° C.

Assignees

• Safran Landing Systems

Inventors

• Mierzejewski Sacha
• Ottenio Romain

Classifications

• C25D5/48

  After-treatment of electroplated surfaces · CPC title

• B60B35/02

  Dead axles, i.e. not transmitting torque · CPC title

• C25D5/34

  Pretreatment of metallic surfaces to be electroplated · CPC title

• C23C22/78

  Pretreatment of the material to be coated · CPC title

• C25D3/562

  containing more than 50% by weight of iron or nickel or cobalt · CPC title