Washing and cleaning according to all relevant Rolls-Royce requirements:

• Steam degreasing in accordance with RPS 128
• Liquid degreasing in accordance with RPS 313

Equipment for dry sandblasting and glass bead blasting

Removal of damage caused by corrosion and erosion from the surface of parts made of light metals; removing silicone rubber from the stator compressor blades and rotor blades; removal of ROCKHARD varnish and anode coating from aluminum alloys.

Cleaning and preparation of parts’ surface to be coated with plasma.

Abrasives: natural corundum (AL₂O₃) and electro-corundum (granulations: 30/40, 60/80, 120/220 and 320/400 mesh), glass beads (40 to 80 µm), quartz (SiO₂), SiC, Diamond.

Within the NDT methods we have:

- testing with liquid penetrants

- magnetic particle testing

- ultrasonic examination

- X-ray examination, radiography

LIQUID PENETRANTS TESTING

Liquid penetrants tests are performed on Magnaflux test lines. The test line consists of:

• penetrant bath,
• drain stand,
• bath for emulsifier,
• rinsing bath,
• drying chamber,
• developer  chamber,
• test chamber under UV light.

The test parts come pre-cleaned and degreased. Tests with liquid penetrants are performed in accordance with the test instructions and in accordance with the standard. Reference samples with a chromed surface are used for daily testing of the sensitivity with liquid penetrants.

The followings are used in the testing process:

a) Fluorescent penetrants:

- water removable fluorescent penetrant of high sensitivity (penetrant, removal agent - water, developer).

After cleaning and degreasing, parts are heated in a special furnace immediately before testing, as necessary. The aforesaid penetrant is used for testing compressor and turbine blades and vanes, gas turbine discs, transmission gears, etc.

- emulsifier removable fluorescent penetrant of high sensitivity (penetrant, removal agent, developer).

This penetrant is used for testing compressor and turbine blades and vanes, shafts, discs, casings and piping of gas turbine.

b) Dye penetrants:

- dye solvent removable penetrant (penetrant, removal agent, developer).

Aforesaid penetrant is used for testing shafts, discs gas turbine piping, gears, etc. This penetrant is also used for spot testing of larger parts, and for testing of welded joints. The device is a portable type.

Penetrants of other sensitivity level may be used, in accordance with the testing and in accordance with appropriate standards, as necessary. Inspection of equipment functioning and the maintenance of the process are performed by "ORAO" Laboratory Division. Inspections are performed according to the instructions for testing process inspection and according to the appropriate standards including the following:

- inspection of penetrant fluorescence intensity,
- inspection of emulsifier,
- inspection of developer,
- inspection of UV lamp intensity,
- inspection of ambient light,
- calibration of all measuring instruments on the testing line.

MAGNETIC PARTICLE TESTING

Magnaflux Interlock System 883 is used for magnetic particle testing, which consists of the following:

- CCH 10 device for power supply of 10000A.
- H 720 device for magnetization,
- HWSL device for magnetization,
- MV 3 device for magnetization,
- SB 1619 device for demagnetization.

Currents for magnetizing workpiece are up to 6000A, and the testing process is the wet one.

 H 720 device for magnetizing is designed for wet testing method, providing low voltage, high amperage of corrected DC, and maximum 6000A output. Magnetizing is performed by current passing through a part or bar for circular magnetization, or by clamping the part between movable and fixed fixture for longitudinal magnetization.

 MV 3 device for magnetization is designed for crack and subsurface crack detection in ferromagnetic material of machined parts, forgings, castings, etc.

The procedure is as follows:

a) passing of high intensity AC current through the part or bar on which the parts are placed in row,
  by which circular magnetic field is obtained. 
b) clamping of the part between two contacts and actuating of two coils by DC, in order to obtain
  longitudinal magnetic field.

HWSL device consists of spiral coil and threaded bar. Basic features are - half-wave current of 4000A intensity, AC current of 4000A intensity.

The testing is performed in accordance with RPS 700 Specification. The following is used during the testing process: Berthold field indicator, MTU No. 3 sensitivity test piece, and the instrument for measuring of magnetic field intensity. The concentration of magnetic particles is checked daily, as well as testing system in accordance with AMS 2641.

ORAO Laboratory Division performs other inspections of system correctness:

- check of UV lamp,
- check of ambient light,
- check of white light intensity,
- check of the contamination of magnetic suspension,
- calibration of measuring instruments.

According to instructions for testing process control and RPS 700 Specification.

ULTRASONIC INSPECTION

       Inspections are performed by use of USM 25S ultrasonic device of Krautkramer manufacturer. Masters are used for measuring range adjusting. Aforesaid method is mostly used for testing of compressor rotor blade body, leading and trailing edge by use of test pieces - blade with artificial defects. Testing is performed by use of surface probes. Compressor rotor I stage disc is tested by special double probe of the device, and test pieces with artificial and actual defects are also used during the testing. Inspection of the testing process is performed by ORAO Laboratory Division.

X-RAY EXAMINATION, RADIOGRAPHY

In this way, metal parts (according to standard EN 444:2002) and welded joints (according to standards EN 1435:2001, EN 1435:A1:2003 and EN 1435:A2:2004) are tested.

Regeneration of parts involves the application of the following coatings:

- "High velocity oxy-fuel" coating process (HVOF)

- Plasma spraying procedure

- Flame spraying procedure

"High velocity oxy-fuel" COATING PROCEDURE (HVOF)

The HVOF process effectively uses high kinetic energy and controlled heating of the powder (coating material) to apply dense non-porous coatings, well bonded, with extremely fine roughness and low residual stresses. The process uses oxygen and a wide range of fuel gases (propane, propylene, hydrogen or natural gas) and air to produce a high-pressure cylindrical flame, which envelops the axially injected powder of the coating material. A cylindrical flame forms a jet of powder, to obtain uniform heating and melting. The flame and powder are accelerated by a convergent-divergent nozzle to supersonic speeds. Velocities above 2130 m/s move powder particles, which are plastically deformed and pasted when struck on the sample. The result of high kinetic energy, which is transmitted to the particles, are coatings with a fine homogeneous microstructure.

The application of the HVOF coating process is in the following industries:

• Aerospace - turbojet turbines, grooves, landing gear, actuators and flap runners.
• Energy - industrial gas turbines, hydroelectric pistons, water turbine blades, injectors and gas turbine blades.
• Automotive - transmission forks.
• Petroleum - pumps, latch valves, butterfly valves, exhaust pipes.
• Production of glass - pistons for casting glass.
• Others - replacement for chrome plating on many parts, agricultural equipment, electrical motors, protective sleeves ...

DEVICE: SULZER METCO Diamond Jet® 9MDE-DJ, hybrid 2600/2700.

Plasma coatings

DEVICES FOR DEPOSITION OF COATING BY THERMAL SPARAYING

DEPOSITION OF COATINGS BY PLASMA SPRAYING

In plasma spray procedure, DC ark is used to generate hot jet of ionized plasma gas, which is a source of heat for the process of spraying. Powdered coating material is entered into plasma jet by inert gas, where it is transformed into plasma gaseous state and at high velocity transferred onto the part being treated. Coatings of high quality are obtained by procedure of depositing coatings by plasma jet, because this is procedure where the combination of high temperatures, forceful energy source, relatively inert medium and high velocities are used.

The advantages of this procedure are as follows:

• Deposition of metals, carbides, or any other combination of these materials;
• Microstructure of coating consists of fine, scattered, axially oriented clusters;
• Possibility of forming homogenous coatings of constant thickness;
• Possibility of quick deposition of coatings (>5 kg/hour).

Deposition of coatings by plasma spraying:

• Deposition of tungsten carbide/cobalt coatings on wearing surfaces of jet engine compressor sealing labyrinth rings, cylinders, pins, etc;
• Deposition of zirconium based thermal barrier coatings (TBC) on combustion chambers and turbine rotor blades;
• Deposition of aluminum and chromium oxide on rollers for laser and diamond engraving;
• Deposition of molybdenum alloys onto piston rings of diesel engines

Primary gas in the process is argon (Ar), and secondary gas is hydrogen (H2) or nitrogen (N2).

DEPOSITIONS OF COATINGS BY FLAME SPRAYING

 The procedure falls into a procedure group for deposition of coatings by thermal spraying. Coating material in this procedure is delivered into device in form of wire or powder. It is heated and transferred to workpiece where the coating is formed. The advantages of this procedure are that coatings are applied easily and are very cheap in comparison with other procedures for deposition of coatings. Burning of fuel-gas is used as the source of heat (usually acetylene or propane) and oxygen. Procedure of deposition of coatings by flame spraying is widely applied where lower prices are required and lower coating quality.

Some of typical applications are: 

• Overhaul of worn out shafts, especially on locations of bearings, with coatings of stainless steel and bronze based alloys. Since the coatings are porous, they keep lubricants and improve lubrication in this way.
• Protection against corrosion of structures and components (bridges, platforms, etc.) with aluminum and zinc coatings. Aluminum is more expensive, but is resistant to aggressive ambient with acid evaporations.
• Zinc is more resistant to alkaline corrosion. Furthermore, this procedure is used for deposition of thermo-plastic polymeric coatings that are resistant to corrosion.

DEVICE: SULZER METCO 14E

The position of the inertial axis of the rotor depends on the distribution of its elements around the circle. If the masses of all mounting units and parts are evenly distributed, the inertial axis coincides with the axis of rotation.

Such a rotor is called balanced. In most cases the masses are distributed unevenly, the inertial axis is movable with respect to the axis of rotation, an imbalance equal to the product of the unbalanced mass and its eccentricity occurs. Such a rotor is called unbalanced. In the case of unbalanced rotors, centrifugal forces proportional to the imbalance and the squaring of the speed of rotation occur.

Dynamic balancing of the rotor is performed on special devices that allow determining the weight and position of balanced weights in two correction planes. Correction planes are called planes perpendicular to the rotational axis and in which the imbalance of the rotor is compensated by removing or adding mass.

Static balancing in ORAO JSC  Bijeljina means balancing of individual disks of which one compressor rotor consists.

PLASMA DEPOSITION OF THERMAL BARRIER COATINGS BY PHYSICAL METHODS FROM VAPOUR STAGE (PVD)

DEPOSITION BY ARC EVAPORATORS

In PVD process, deposition of material is performed atom by atom, through condensation from gas Plasma State into solid state – formation of coating on the surface of workpiece.

Characteristics of electric arc, concentration of plasma column, which is in contact with discharge electrode, i.e. formation of area of extremely high current density on cathode surface called cathode spot, are used in the plasma process for depositing thermal barrier coatings. In area of cathode spot direct evaporation of material without melting occurs, because only local heating is performed and fast movement of one or more spots over the electrode surface. Good features of arc evaporators are high velocity of deposition, simple design, and high ionization level of particles in arc plasma (up to 50%). Therefore, it is possible to deposit quality coatings with very good adhesion on base of different materials. The deposition homogeneity on samples of complex space geometry is achieved by positioning more arc sources at various places inside the chamber and high ionization level of metal and gas vapor in contact with the sample surface.

DEVICE:    VPT-12M

Application of deposition by arc evaporators:

• deposition of thermal barrier coatings, M-Cr-Al-X coatings onto turbine rotor and stationary gas turbines blades, which are exposed to temperatures of 1600 ˚C.
• deposition of hard coatings onto various tools.
• deposition of decorative coatings.

"ORAO" JSC  performs complete equivalent, homologation and verification tests of aircraft engines and their components. We have two test cells for testing of turbojet engines.

The turbojet engine test cell in Bijeljina is equipped with a modern data acquisition system and is used for testing Rolls-Royce Vipers of all series, it is capable  to test engines up to 10,000 daN thrust.

The test cell for testing turbojet engines in Batajnica is equipped with a modern data acquisition system and is used for testing engines R13-300, R25-300 and RD-33 (II series), it is capable to test engines up to 12000 daN thrust.