FIELD OF INVENTION

The present invention relates to a test unit for inspection of hardness of flame hardened zone in turbine blades. More particularly, the invention relates to an apparatus for testing flame hardness of a quench hardened steam turbine blade tip section to the inlet end of the steam.
BACKGROUND OF INVENTION
The steam inlet edge of a low pressure (LP) turbine moving blade continually erodes because of the collision of condensed water droplets mixed in flow loss. As a countermeasure for this erosion, a section of the blade material at the inlet end is preferred to be agreeing to have a high hardness to prolong blade life. Conventionally, the effects of this high hardness section were secured by many methods such as by silver brazing or welding process for mounting a high-hardness material HHM to the blade main body. Other popular and sought after procedures to have a high hardness blade section at the inlet end of the moving blade includes part hardening of the blade section by gas flame hardening process. However, flame hardening brings with it operational issues such as improper or insufficient pressure and temperature control, the ratio control of the combustion gas and oxygen in flame, the shape of the flame torch or the distance of the moving blade from the flame, the moving speed precise flame target and hard to control hardness range in a selective area such as the blade tip. Furthermore, when the leading

edge thickness is extremely thin, and this part is heated more than the other part of the required hardness of the possibility of the occurrence of a crack or even seizure.
The testing methods as per prior art included performing the hardness testing with setup which was rigid and the test being performed manually which not only naturally enhanced the system inaccuracy because of the degree of operator dexterity involved but also resulted in expensive time delays in blade and probe settings. The method previously known for hardness checking was being carried on Turbine blades by holding it manually either vertically or horizontally. At times holding the hardness measuring probe at right angles to the surface of the blade was difficult due to hand vibration, uneven hand pressure, complicated aerodynamic profile of the blades, uneven weight of the blade etc. resulting in erroneous measurement of hardness.
It is of utmost importance that the hardness measuring probe is kept at certain angles on the blade surface where hardness is being measured. Thus, in order to establish such rotor blade flame hardening process it is desired that a test setup be constructed for hardness inspection of flame hardened zone in turbine blades.
We have discovered that through the use of test setup as discussed herein will not only save cost expensive operation time but will also provide great and continuing accuracy inherent in its design and operation, ruggedness and simplicity in its construction.
OBJECTS OF THE INVENTION

Therefore it is an object of the invention to propose a test unit for inspection of hardness of flame hardened zone in turbine blades, which is capable of inspecting hardness of flame hardened zone of turbine blades.
Another object of the invention to propose a test unit for inspection of hardness of flame hardened zone in turbine blades, which is able to improve the reliability and service life of the flame hardened blades and hence of the turbine.
A still another object of the invention to propose a test unit for inspection of hardness of flame hardened zone in turbine blades, which eliminates the system inaccuracy caused by manual testing of holding the hardness measuring probe by hand in prior art.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The foregoing and other features of the invention, comprising test setup and associated method for hardness inspection of flame hardened zone in turbine blades together with the construction and relative arrangement of the several parts, will be apparent from the following more particular description of the invention, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different figures and subsequently incorporated in the subjoined claims.

The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention and in which:
Figure 1 shows a line representation of a flame hardened turbine blades, in
accordance with the present invention.
Figure 2 shows a line representation of test setup for hardness inspection of flame
hardened zone in turbine blades, in accordance with the present invention.
Figure 3 shows a line representation of head clamp arrangement of the test setup
for hardness inspection of flame hardened zone in turbine blades, in accordance with the present invention.
Figure 4 shows a line representation of tail clamp arrangement of the test setup for
hardness inspection of flame hardened zone in turbine blades, in accordance with the present invention.
Figure 5A,5B shows a line representation of probe clamp arrangement of the test setup for hardness inspection of flame hardened zone in turbine blades, in accordance with the present invention.

Figure 6 shows a line representation of T-Slots in base plate arrangement of the test
setup for hardness inspection of flame hardened zone in turbine blades, in accordance with the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Before describing in detail the present invention of a test setup and associated method for hardness inspection of flame hardened zone in turbine blades, it should be observed that the present invention resides primarily in a novel and non-obvious combination of hardware elements and method steps. Accordingly, these elements and steps have been represented by conventional elements and steps in the drawings, showing only those specific details that are pertinent to the present invention so as not to obscure the disclosure with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
Figure 1 shows the optimally flame-hardened blade surface that has been heat treated through a flame hardening process to exhibit uniform distributions of the hardness and residual compressive stress over the treated area 2 of length L and Width W. Hardness in depth of around 1 mm is required in turbine-rotor blade 1 at leading edge for better performance but by using flame hardening.

Hardness of these blades are checked at plurality of distal locations from outer diameter of the blade profile, where L is the length of hardened Zone in close proximity from the transition zone of the treated area 2.
The present test setup is constructed which can not only hold the blade rigidly at required angles for hardness inspection of flame hardened zone in turbine blades which will improve the reliability and service life of the flame hardened blades, and of the turbine thereof.
Referring now to figure 2, the basic method is to flexibly hold all the sub parts of the inventions together to workbench 20. The T-Slots 21 are specially shaped channels that run along the length of the workbench 20. As shown in figure 6, a plurality of T-slot 21 are generally configured into the solid material 22 of the table 20. The T-Slots affords the machinist user with the limited ability to attach vises and other work holding devices. Tools such as T-Nuts, Step Blocks, and Threaded Rods etc. are used to securely clamp the work holding devices or the likes to the planar surface 26 of workbench 20.
Atleast a hole 25 is provided to threadedly hold the workbench 20 on other more ergonomic or more technological means such as a test table, if required.
For standardization of hardness inspection of flame hardened zone in turbine blades, this test unit 10 is provided with blade holding clamping arrangements 30, 40 to rotatably support and hold turbine blade 1 during the inspection process. These clamps 30, 40 hold the blade and provide the blade an initial angular orientation with reference

to the inspection probe 60. The provisions for holding, and accurately positioning, the probe 60 to test the hardness in treated area 2 are provided through probe clamping means 50 which provide a further orientation of the inspection probe 60 with respect the flame hardened blade surface.
Referring now to figure 3 in detail, threaded means such as T-Nuts are used to securely clamp the base 39 of the head clamp means 30 to the planar surface 26 of workbench 20. To provide strength and stability to the head clamp and to provide a stable base for hanging blade load during inspection, stiffeners 32 are welded on base plate 39. While the threaded lock 35 is untightened, the blade leading edge 2 is first held securely in clamp pads 36 of clamp 31 by different sides by tightening blade locking means 37. Once the blade is held, set of gear arrangement in frame 33 is operated by the test operator through rotary lever 34 connected at one end of the frame while the other end of the frame is connected to clamp means 31 through bracket member 38. When a selective rotary input is provided through rotary lever, it rotates the blade 1 to provide it the required angular orientation with respect to the test probe in probe clamping means in order to expose the treated area 2 of the blade for inspection purposes. At this angular orientation, thread locks 35 are tightened to lock the blade 1.
Referring now to figure 4 in detail, threaded means such as T-Nuts are used to securely clamp the base 45 of the tail clamp means 40 to the planar surface 26 of workbench 20. While the threaded lock 42 of rotary unit 46 is loose, the clamping unit 41 is provided with a selective initial rotation to adjust the orientation of clamping unit with

respect to the blade. The blade root 4 is mounted at this angular position between the clamp pads 41. When threaded means 44 are tightened it actuates clamp pads 41 to hold the blade root rigidly in clamping unit 41.
Referring to figure 5 in detail, a probe clamping means 50 is shown positioned across the blade axis. Threaded means such as T-Nuts secure the base 53 of the probe clamping means 50 to the T-slots on planar surface 26 of workbench 20. The base plate 53 of the probe securing means 50 is provisioned with atleast one slot 53’ towards the center and along the length of the base plate. The probe clamp means 50 is provisioned to perform on the basis of atleast two rotary inputs, provided through rotary handles 51, 52 to control the position of the test probe 60 with respect to the flame hardened blade surface 2 of the blade clamped in clamping means 30, 40.
The clamps 30, 40 and 50 and workbench 20 are made of aluminium or steel. Once the base plate 53 is secured on the workbench 20, a rotational to linear translational drive system 61 such as a lead screw block or the likes having an internal threaded portion is threadedly positioned across the length of base plate 53 to threadedly receive rotatable lead screw 55A using threaded means 63, as shown in figure 5. The distal end of the lead screw 55A pushes a movable unit 57 across the length of blade.
The movable unit 57, adapted to travel along the lead screw 55A, is made up of flexibly connected bracket members 57A, 57B, 57C. The rectangular base plate 57A is placed upon base plate 53. Threadedly mounted upon said base plate 57A are vertically

and parallel disposed support slotted plates 57B which may likewise be of metal. Top plate 57C is suitably clamped utilizing the slots 57’ in slot plates 57B to form a carriage or movable unit 57.
Over the carriage 57 is a within which may be secured a specimen, schematically indicated at 38, in line with the axis x-x of the source of radiations and the window of the detector.
Rectilinear motion to a movable carriage along linear guide means by a rotatable lead screw positioned parallel to said guide means, a carriage drive mechanism connecting said carriage to said lead screw for providing said motion independently of irregularities in said lead screw, said carriage drive mechanism comprising.
Thus the movable provide in this manner execute the probe movement across the blade as the system 61 is used or translation of rotary input from lever 55A to require linear movement.
The rotary handle 51 provides fine adjustments in linearly traversing the test probe in a direction across the width of the blade through an input to lead screw 55 while the rotary handle 52 along with vertical column 53 helps in performing finer adjustments in spatial position of the test probe 60 on a vertical axis. The test probe 60 is threadedly clamped in clamping pads of probe securing means 54. The probe securing means 54 is threadedly clamped on threaded vertical column 53 so that the height of probe can be adjusted when a rotary input is provided by handle 52. The probe securing means 54 are

also connected to a threaded kinematic pair means 55 so as to provide it, or in turn to the test probe secured in it, a lateral motion towards and away from the blade 1 when a selective rotary inputs is being provided through handle 51. On the column by using this arrangement the surface of the blade and probe can be made perpendicular to each other.
The system 61 provides a relatively maintenance free mechanism with low starting torque and high positional accuracy.
The hardness test such as UCI Method Ultrasonic Contact Impedance (UCI) is performed in which when the Vickers diamond in the probe held in probe clamp 50 contacts the flame hardened area 2 the resonant frequency changes. This change happens in relation to the size of the indent area from the Vickers diamond. The size, in turn, is a measure for the hardness of the treated or hardened area 2 of the blade 1.
The rotary input from lever 34 for angular orientation of the blade and the linear input to the probe 60 by probe clamping means 50 are iteratively provided for fine adjustment of the trated over with reference to the probe and vice versa.
The flexibility in the clamping arrangement makes it extremely easy to quickly orient the blade surface of the blade and the test probe relative to each other as per the testing requirements thus making it a perfect position to check the hardness accurately and correctly while the flexibility in positioning of clamps 30, 40 makes test unit 10 more robust to cater to a wide variations and configuration of blade.

This flexibility in angular orientation of blade and movement and fine adjustment control not only provide a test setup that ensures repeatability of hardness tests but also caters to the requirements of performing hardness test at a range of inspection angles as the leading edge 2 is particularly skewed to conform to the complex aerofoil 3 design of the hardended blade.
The clamps 30, 40, 50 as well as workbench 20 is manufactured from aluminum or steel material. Other materials, well known to those designing and constructing machine tool accessories may be substituted without departing from the spirit or intent of this application.
Further, it will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

WE CLAIM:-

1. A test unit (10) for inspection of hardness of flame hardened zone in turbine blades, the said test unit comprising;
a workbench (20) for holding flexibly all the sub parts of the testing unit;
a head clamp means (30) with its base (39) rigidly fixed by threaded means to the planar surface (26) of workbench (20), the said clamp means (30) disposed for holding the blade (1) and for receiving selective rotary input from a rotary lever (34) to orient the blade (1) for providing the required angular orientation with respect to the test probe (60) to expose treated area (2) of the blade for inspection;
a tail clamp means (40) with its base (45) rigidly fixed by threaded means to the planar surface (26) of the workbench (20), the said clamp means (40) disposed for holding the other side of the blade (1), a clamping unit (41) providing a selective initial rotation for adjusting the orientation of clamping unit (40) with respect to the blade;
a probe clamping means (50) with its base (53) rigidly fixed by threaded means to the planar surface (26) of workbench (20), the said clamping means (50) is actuated on the basis of the rotary inputs provided through rotary handles (51, 52) for controlling the position of the test probe (60) with respect to the flame hardened blade surface (2) of the blade (1) clamped by clamping means (30, 40).

2. The test unit (10) as claimed in claim 1, wherein the rotary handle (51) is configured
for fine adjustments in linearly traversing the test probe (60) in a direction across the width of the blade (1) through an input to lead screw (55).
3. The test unit (10) as claimed in claim 1, wherein the rotary handle (32) along with
vertical column (53) is configured for making finer adjustments in spatial of the test probe (60) on a vertical axis.
4. The test unit (10) as claimed in claim 1, wherein the test probe (60) is threadedly
clamped in clamping pads of probe securing means (54), the said probe securing means (54) is threadedly clamped on threaded vertical column (53) so that the height of probe (60) can be adjusted when a rotary input is provided by handle (52).