Stainless steels are the most commonly used materials for cavitation repair. The cavitation rates of selected materials, measured in accordance with ASTM G 32 vibratory cavitation test, are shown in Table 1. These rates should be used as an indication of relative-not absolute-wear rates. Several materials, such as cobalt and nickel-based Stellite® alloys and advanced iron based alloys such as Ireca, have superior cavitation resistance compared to stainless steel (Simoneau 1987, 1991). The detailed compositions of these and other materials are shown in Tables 2 and 3. Some of these alloys are now also available in powder form suitable for application by HVOF or plasma spray processes.
Source: Simoneau 1991.
The highly cavitation-resistant Ireca steel weld alloy, which was developed by Hydro Quebec and was marketed as Hydroloy® 913 by Stoody Corporation in the early 1990s, has been used with success on cavitation-prone areas of hydroelectric turbine runners. However, the alloy was difficult to weld and grind and is no longer marketed by Stoody. Hydro-Quebec's Ireca steel, following further research and alterations, is now marketed by Castolin Eutectic Corporation under the brand name CaviTec®1 (Fulton 1996).
Co |
Cr |
Mo |
Ni |
Mn |
Fe |
Si |
C |
W | |
Tribaloy® T-4002 |
Bal. |
8.50 |
28.5 |
1.5 |
1.5 |
2.6 |
<0.08 |
- | |
Tribaloy® T-7001 |
1.50 |
15.5 |
32.5 |
Bal. |
1.5 |
3.4 |
<0.08 |
- | |
Tribaloy® T-8001 |
Bal. |
17.5 |
28.5 |
1.50 |
1.5 |
3.4 |
<0.08 |
- | |
Stellite® 61 |
Bal. |
28 |
3 |
3 |
3 |
1.1 |
4 | ||
SAE 1020 |
0.2 |
Bal. |
0.2 |
0.2 |
|||||
430 Stainless
|
14-18 |
1.0 |
<0.5 |
Bal. |
<1.0 |
<0.12 |
|||
431 Stainless
|
15-17 |
1.0 |
1.25-2.5 |
Bal. |
<1.0 |
- | |||
308 Stainless Steel* |
20 |
2.0 |
8.9 |
Bal. |
0.83 |
0.04 |
- | ||
309 Stainless
|
22-24 |
2.0 |
12-15 |
<1.0 |
|||||
316 L |
17 |
2.5 |
13 |
Bal. |
1 |
0.03 |
- | ||
Metco 71 VF-NS-13 |
12 |
- |
- |
- |
1 |
- |
4 |
Bal. | |
Nistelle® C1 |
2.50 |
16.50 |
17.00 |
Bal. |
5.75 |
1.0 |
0.12 |
4.5 | |
Nistelle® D1 |
1.50 |
0.75 |
- |
Bal. |
2.0 |
9.25 |
0.12 |
- | |
Co |
WC |
||||||||
Sylvania Osram 150A |
17 |
83 |
|||||||
B |
Cr |
Mo |
Ni |
Fe |
Si |
C |
Cu | ||
NiCrBSi Alloy |
4.0 |
16.0 |
3.0 |
Bal. |
2.5 |
4.0 |
0.05 |
3.0 | |
Zr |
Al |
Ni |
|||||||
85-15 Zn-Al |
85 |
15 |
|||||||
Ni - 5 Al |
5 |
95 |
|||||||
* Simoneau 1991.
** Typical composition (Fontana and Green 1987).
Other advanced iron-based cavitation-resistant alloys that have recently entered the market include Hydroloy® 914, marketed by Stoody Corporation; NOREM®4, developed by the Electric Power Research Institute (EPRI); and D-CAV®5, marketed by Demand Arc, Inc. (Table 3). Compared to Hydroloy 913, Hydroloy® 914 contains higher silicon content (up to 5 percent) along with an increase in nickel to 2 percent (Menon, Moiser, and Wu, 1996). Hydroloy® 914 is presently available only as weld wire and not in powder form for thermal spraying.
NOREM® is a cobalt-free iron-based alloy originally developed for the nuclear industry, but has applications in the hydroelectric area as well. An advantage of NOREM® and D-CAV® is the lower cost compared to cobalt-based alloys. NOREM® is available in both wire and powder forms. D-CAV® is a proprietary austenitic stainless steel and is available only in wire form. Although some of these advanced materials are not currently available in powder form suitable for thermal spray application, their reported excellent cavitation resistance warranted inclusion in the test matrix. It is hoped that these alloys will be available in the future in powder form.
* Simoneau 1991.
** Menon, Moiser, and Wu 1996.
*** Orkin 1995.
1 Castolin Eutectic Corp., Charlotte, NC
2 Stoody Deloro Stellite, Inc., Goshen, IN
3 Sulzer Metco, Inc., Westburry, NY
5 Demand Arc, Inc., Chattanooga, TN