ICET
INTERNATIONAL CAVITATION EROSION TEST

a worldwide cavitation erosion research project co-ordinated by
the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences
(IMP PAN), Gdańsk, POLAND

Test Co-ordinator:	Dr Janusz Steller, IMP PAN	Test Panel Members:	Dr Tadeusz Krzysztofowicz, Technical University of Gdańsk, Poland
Test Secretary:	Dr Bolesław Gireń, IMP PAN		Dr Andrzej Lichtarowicz, University of Nottingham, U.K.
			Prof. Hartmut Louis, University of Hannover, Germany
			Prof. Marian Mazurkiewicz University of Missouri, Rolla, U.S.A marianm@umr.edu

Test Objectives

 compilation of data on design and operation of existing test rigs,

 comparison and correlation of the damage course and cavitation resistance assessments

 of selected groups of materials tested under different cavitation conditions,

 establishment of relationships between the damage course and the parameters defining

 cavitation load conditions,

 creation of the basis for further standardisation of the methods used to assess material

 resistance to cavitation damage.

Participating Laboratories

No.	Laboratory	Contributor
1.	Institute of Water Problems of the Bulgarian Academy of Sciences (IWP Bulg.Ac.Sci), Sofia, Bulgaria	Andon Nikolov
2.	China Ship Scientific Research Centre (CSSRC), Wuxi, China	Zhiye Ji
3.	Tsinghua University, Beijing, China	Jitang Huang
4.	Technical University of Ostrava (VSB), Ostrava, Czech Republic	Jaromir Noskiević¹⁾
5.	SIGMA Research Institute, Olomouc, Czech Republic	Alois Koutny²⁾
6.	VEAG United Power Plants Co., Hohenwarte II Pumped Storage Power Plant, Hohenwarte, Germany	Klaus Junghanß³⁾ Erich Dimter
7.	University of Hannover, Hannover, Germany	Hartmut Louis
8.	KSB AG, Frankenthal, Germany	Peter Hergt³⁾ Gerd-Heinz Bauer
9.	Fluid Control Research Institute (FCRI), Palghat, India	M.S.Konnur
10.	CISE S.p.A., Milan, Italy	Remo Martinella⁴⁾
11.	Hiroshima University, Higashi Hiroshima, Japan	Masanobu Matsumura
12.	Institute of Fluid-Flow Machinery of the Polish Academy of Sciences (IMP PAN) Gdańsk, Poland	Janusz Steller⁵⁾
13.	University of Cape Town, Rondebosch, South Africa	Anthony Ball⁶⁾
14.	University of Hull, Hull, United Kingdom	Robert D. James
15.	The City University, London, United Kingdom	Peter A. Lush

¹⁾	Professor Jaromir Noskievic died in 1997. Following his successor, Professor Jaroslav Janalik, nobody continues his cavitation erosion research at the VSB Chair of Hydraulic Mechanics and Equipment.
²⁾	The SIGMA concern was dissolved in 1990. According to Dr Alois Koutny all the cavitation erosion test facilities have been taken over by the ČKD Blansko Company. Dr A.Koutny is now a managing director of the LASER-TECH Ltd., Olomouc, Czech Republic.
³⁾	retired
⁴⁾	The CISE Company does not seem to exist any more. Our numerous attempts to contact Dr R.Martinella or his co-worker, Dr A.Fialdini, have failed completely.
⁵⁾	Dr Janusz Steller replaces Professor Kazimierz Steller who died in May 1992. Professor Kazimierz Steller was the ICET initiator and the first co-ordinator. He was also responsible for providing all the IMP PAN experimental data.
⁶⁾	Professor Anthony Ball passed some time after our seminar in 2000.

Test materials

general description	commercial name
Armco iron	E04
aluminium alloy	PA2
carbon steel	45
acid resistant steel	1H18N9T
single-phase brass	M63
polyamide 6 plastics	tarnamide

The ICET programme, proposed to the Potential Test Participants, has covered tests on 6 materials listed in the table on the left. Test materials have been selected in a way providing evident differentiation between their erosion curves - it can be easily noticed that two of them (Armco iron E04 and aluminium alloy PA2) are typical reference materials used in numerous erosion tests while the next three ones (carbon steel 45, stainless steel 1H18N9T, and single phase brass M63) are structural materials commonly applied in engineering practice. All the metallic materials were acquired at the CENTROSTAL Steel Storehouse, the main distributor of metals in Poland while the polyamide 6 plastics was obtained from the CHEMIPLAST EVG in Gliwice. Chemical composition, heat treatment conditions and values of some mechanical parameters of metallic materials as well as are to be found in the ICET documents.

Experimental rigs and photographs of eroded specimens

Almost a half of tests were carried out using vibratory rigs . The vibration frequency of these rigs is usually close to 20 kHz which corresponds to the ASTM G-32 Standard . An exception is the IMP PAN lab with a facility of 8 kHz vibration frequency. Much wider diversity can be noticed in vibration amplitudes, sizes and mounting methods of test samples. Vibration amplitudes smaller than those recommended by the ASTM G-32 Standard are often the case ( CSSRC, IWP Bulg.Ac.Sci., University of Hiroshima and Tsinghua University). Counter-samples are applied as a rule in 2 labs (Universities in Cape Town and Hull ). Three further labs (University of Hiroshima, IWP and the Technical University of Ostrava ) use stationary specimens occasionally. As it is generally known, this technique enables testing light and brittle materials. Vibrating specimen buttons are usually screwed in the horn (ASTM G-32 Standard). A specimen is screwed on the horn in the Czech Republic ( Czechoslovakian standard CSN-015082-76 ) whereas a mounting nut (Polish Standard PN-86/H-04427 ) is applied only in the IMP PAN.

Cavitation tunnels involved in the ICET programme show a significant differentiation in the test chamber design. Tests were conducted in two tunnels with cylindrical cavitator ( the Hohenwarte Pumped Storage Power Plant in Germany and the IWP in Bulgaria), two tunnels with wedge cavitators ( City University, London, and CSSRC, Wuxi, China) and two tunnels with barricade and counter-barricade systems (Universities of Hiroshima and Hannover ). The majority of cavitation tunnels are not used for tests of highly resistant materials.

From among four rotating disks involved in the ICET project, two facilities are of similar design. Both in the CSSRC and the SIGMA Research Institute (Olomouc, Czech Republic) cavitation has been generated by holes drilled in the disk upstream of the test samples. Cavitators in form of cylindrical bolts are applied in the IMP PAN and the KSB laboratory in Frankenthal (Germany). However, the samples are mounted at the disk in the IMP PAN and on the stagnator vanes in the KSB lab.

Cavitating jet tests have been carried out in the FCRI (Palghat, India) and at the University of Hannover. Both rigs follow exactly the design of Dr A.Lichtarowicz of the University of Nottingham ( ASTM G134-95 Standard).

It has been only the SIGMA Research Institute which has offered us tests carried out at a liquid impact device . As it is generally known this kind of a device was widely used in the past to assess the cavitation erosion resistance of materials.

Main parameters of the test rigs involved in the ICET programme are to be found in the ICET documents.

Test Programme

Test Participants have been asked to conduct erosion tests at least 2 specimens of each kind under specified steady state conditions. As usual, it was recommended to continue the tests as long as needed in order to attain the steady-state damage period. It was assumed that the data submitted on the Measurement Cards would comprise main operating parameters of the facility as well as tables of mass/volume losses in course of the test, final values of the mean and maximum depth of pits, data on microhardness distribution, photographs of damaged surfaces and their metallographic structure.

Most experimental results are available through the ICET database. Installation files of this database are attached to this document and the ICET Preliminary Report available from the Test Co-ordinator . This report was assumed to form a basis for discussion during the ICET Seminar held on June 1st and 2nd 2000 in the WDW Hotel Complex in Sopot. The main conclusions following from the test results and the discussions held during the Seminar will be summarised in the Final Report to be issued in the beginning of 2001.

Results - general survey

Most of the rigs were used to test all the metallic materials. However, some tests had to be abandoned. In few cases the Test Co-ordinator was not able to submit material samples of sufficient size and one cavitation tunnel appeared not suited for testing highly resistant materials, like carbon steel 45 or chromium-nickel steel 1H18N9T.

Severe difficulties occurred at numerous facilities when testing the polyamide 6 (tarnamide) plastics. Tests had to be abandoned at some vibratory rigs, including those designed according to the ASTM G-32 standard, as in view of extremely low density of the tarnamide plastics, there was no possibility to keep the horn/sample system in resonance at the prescribed frequency. Due to water absorbing properties of the tarnamide plastics no mass loss was observed during tests at low cavitation rates.

The scatter in test duration (from 30 minutes for aluminium at the liquid impact rig in Olomouc up to 365 hours for tarnamide in the cavitation tunnel in Hiroshima) can be attributed to a very wide spread of erosion rates. In spite of significant flexibility shown when selecting test duration, in numerous cases the steady-state period was not attained - sometimes due to the test having been stopped during the damage rate decrease, but quite often due to the deceleration period being immediately followed by a further rise of erosion rate.

Differences in cavitation intensities are manifested by an extremely wide range of absolute volume losses and mean depth of erosion after a comparable exposure period (e.g. 1.67 mm³ volume loss and 2.8 mm erosion depth in an aluminium specimen after a 1400 min test in the CSSRC cavitation tunnel and 1.32 cm³ volume loss and 2 mm erosion depth after a 1200 min test of the same material at the rotating disk in the IMP PAN lab).

Results of the preliminary analysis to be found in the ICET documents and other references can be summarised as follows:

Different design features and operating parameters of test rigs lead to differen-tiated assessment of cavitation resistance of materials. Inversions in material ordering between carbon steel 45 and chromium nickel steel 1H18N9T and between Armco iron and M63 brass resulting from assessments by means of single-number parameters appear to be quite a common case.
Mean depth of erosion penetration curves resulting from Armco iron, carbon steel and chromium nickel tests at different vibratory rigs confirm the amplitude effect although in case of the IMP PAN rig, vibration frequency seems to be of essential significance and in case of the facility in the Hiroshima University lab, the temperature effect should not be neglected.
The ratios between erosion rates at various facilities depend substantially on the material tested. In case of the IMP PAN rig, the effect can be attributed to an essential difference in the structure of cavitation impacts distribution. Straightforward correlations between scaling laws and erosion resistance should be avoided as the damage rate ratios for chromium nickel steel are much closer to the ratios for Armco iron than for carbon steel.
The scatter of Armco iron damage rates in cavitation tunnels and rotating disk facilities appears to be higher than that at vibratory rigs. The basic reason can be seen in different design of rigs. Erosion intensity in tunnels with a single ob-stacle is generally higher than in those with barricade-counterbarricade systems despite of lower undisturbed flow velocities applied. It can be suspected that the collapse of cavitating vortices shedding from a cylindrical bolt or wedge results in much more powerful pressure pulses at the wall perpendicular to their axis than the collapse of bubbles and vortices developing in downstream a slot parallel to a test specimen.
Cylindrical bolts appear to be effective cavitators at rotating disks as well. The highest erosion rate was obtained at the IMP PAN facility with cylindrical bolt used as cavitator and test specimen situated at the disk surface. Holes applied as cavitators (SIGMA, CSSRC) seem to be much less effective even if higher peripheral velocities are applied.
A general trend of damage rate differentiation rising with decrease of cavitation intensity for each kind of facilities can be observed. Some exceptions from this rule (IMP PAN vibratory rig, SIGMA rotating disk) can be attributed to substantial differences in design features and operating parameters resulting probably in a significant fraction of high amplitude impacts in the total cavitation loading.

ICET Seminar

ICET results and related topics were discussed during the ICET Seminar held on June 1st and 2nd 2000 in the WDW Hotel Complex in Sopot seaside resort. The Time Schedule of the Seminar included discussion on the Co-ordinator's Report, oral presentations by the Seminar Participants and workshop meetings. Priority was given to the following items:

experience following from the ICET results
experience on cavitation erosion test techniques
prospects of further development and/or standardisation of cavitation erosion test techniques and methods of assessing material resistance to cavitation
material performance prediction under field conditions

Seminar Proceedings are available from the Test Co-ordinator.

Documents

ICET Preliminary Report. Part I: Co-ordinator's Report. IMP PAN Rep. 19/1998
ICET Preliminary Report. Part II: Experimental Data. IMP PAN Rep. 20/1998
ICET database MS Excel files available directly from the download page
ICET Seminar Proceedings. IMP PAN Rep. 235/2000
Schematics of test facilities and photographs of some eroded specimens now available from this page.
Source data submitted by the Participating Labs to the Test Co-ordinator (available at the IMP PAN )

Other reports & publications

1. Steller J.: International Cavitation Erosion Test. Test facilities and experimental results, 2eme Journées CAVITATION, Societé Hydrotechnique de France, Paris 1992

2. Steller J.: International Cavitation Erosion Test. Survey of test facilities Int. Symp. on Cavitation and Erosion in Hydraulic Structures and Machinery, Nanjing (China) 1992, pp.51-59

3. Steller J.: Internationaler Versuch zur Kavitationserosion. Pump Congress Karlsruhe'92, October 1992, Paper B4-06, Fachgemeinschaft Pumpen im VDMA, Frankfurt/M. 1992

4. Matsumura M., Oka Y.I., Sakamoto A.: Quantitative prediction of erosion damage to metallic materials exposed to cavitation attack, Proc. 3rd Int. Conf. on Cavitation, Cambridge 1992, pp.81-85

5. Steller J.: International Cavitation Erosion Test - summary of results. Proc. 3rd Int. Conf. on Cavitation, Cambridge 1992, pp. 121-132

6. Steller J.: Międzynarodowy Kawitacyjny Test Erozyjny. Wyniki wstępne.[w:] "Problemy energetyki wodnej ze szczegółowym uwzględnieniem hydraulicznych maszyn wirnikowych". HYDROFORUM, Sympozjum'91, Wyd. IMP PAN, Gdańsk 1994, s. 177-198

7. Sakamoto A., Funaki H., Matsumura M.: Influence of galvanic macro-cells corrosion on the cavitation-erosion. Durability assessment of metallic materials. Wear 186-187(1995)

8. Klein M.: Relationship database of the International Cavitation Erosion Test. Description of the EROSION v.2.0/97 application. IMP PAN Int.Rep. no. 562/97 (in Polish)

9. Steller J.: International Cavitation Erosion Test and quantitative assessment of material resistance to cavitation. Wear, Vols. 233-235 (1999), pp.51-64

10. Steller J.: Ocena odporności kawitacyjnej materiałów konstrukcyjnych w świetle wyników Międzynarodowego Kawitacyjnego Testu Erozyjnego. [w:] HYDROFORUM 2000, "Hydrauliczne maszyny wirnikowe w energetyce wodnej i innych działach gospodarki", Czorsztyn, październik 2000. Materiały Konferencyjne, s.614-626