Organization of hydrogen energy technologies training

I was attending training program on samples preparation at University of Poitiers, Metallurgic Physics Laboratory.

2007.03.10 – 03.30

Content of the report

• Surface preparation;• Surface roughness

measurements;• Vickers hardness test.

Surface preparation

The objective is to produce the surface for analysis. The following procedures are recommended for preparation of samples suitable for microscopy examination:

•Physical grinding;•Polishing.

Physical grinding

Grinding/polishing machine for 200 mm disc and 2 speeds, 150/300 rpm RotoPol - 22 Silicon carbide paper

Experimental resultsa b

c d

Sample (Ni based

superalloy) surface grinding parameters:

a)P800 5 min 5 N;

b)P1200 5 min 5 N;

c)P2400 15 min 5 N;

d)P4000 20 min 5 N.

Polishing

Aerosol spray made with polycrystalline diamond mixed with a liquid carrier. The carrier quickly evaporates after application, leaving a uniform layer of diamond particles on the cloth.

Non-woven textile buffed to eliminate high peaks, creating a flat polishing surface

Alumina Powder is specially treated to reduce the number of agglomerates

Experimental resultsa

dc

b

e

Sample surface after polishing with

a) 6 μm, 15 min

b) 3 μm, 15 min

c) 1 μm, 20 min

d) ¼ μm, 20 min

e) Al suspension (0.1 μm, 30 min)

Surface roughnessmeasurements

Talysurf CCI System

• 3D surface profiling with high accuracy

• Coherence Correlation Interferometer is non-contact and non-destructive

• suitable for profile peaks between 1nm and 100um in height

0.01nm resolution

• high speed data aquitision and analysis

How It Works

Optical schematic of interference microscope used to measurement for surface structure

Mirau interferometer

Experimental results

Sample surface after polishing with Al suspension

Sq = 0.05028 μm

Sa = 0.03854 μm

Experimental results

Sample surface after grinding with P4000 abrasive paper

Vickers Hardness Test experimental

technique

The CSM IndentationTesters

General principle of the nano indentation apparatus

Vickers Hardness Test

Nanoindentation testing

Surface profile after unload

Typical nanoindentation curve for an elastoplastic material

Experimental results

Micro hardness measurement graph of nonnitrided sample (500 mN)

Micro hardness measurement graph of nitrided sample (500 mN)

Experimental resultsMicrohardness measurements (Ni based super alloys)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 200 400 600 800 1000 1200

F, mN

HV

nitrided sample microhardness measurements

None nitrided sample microhardness measumrements

Microhardness measurements (Stainless steal 316L)

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700 800 900

F, mN

HV

Nitrided sample microhardness measurements

Penetration depth

nitrided (μm)

Penetration depth

nonnitrided (μm)

Normal force

Operation length

0.68 0.7 50 15 s

0.99 100

0.98 1.4 200

1.68 2.3 500

2.91 1000

Penetration depth (μm)

Normal force (μm)

Operation length

0.75 50 15 s

1.88 200

3.57 400

6.04 800

Conclusion

• After surface treatment with physical grinding and polishing we got quit flat surface which is proper for microscope examination.

• Microscope interferometer is effective and nondestructive method for determination of the surface profile

• Nano hardness tester let us know the mechanical properties of very small and localised regions of material surface.

• Nano hardness tester let us know mechanical properties of coatings and thin films without influence of substrate.

• From nano hardness measurements results we can make a conclusion that nitriding is effective way to improve mechanical properties of metals.