Hydro-quebec

Centre National De La Recherche Scientifique

Raynald Simoneau

Antonio Di Vincenzo

Jean-Marc Pelletier

Jean-Paul Boillot

Lucien Chincholle

An austenitic stainless steel alloy showing a high cavitation erosion resistance making it particularly useful for the manufacture and/or repair of hydraulic machine components. The alloy consists essentially of from 8 to 30% by weight of Co; from 13 to 30% by weight of Cr; from 0.03 to 2.0% by weight of C; up to 0.3% by weight of N; up to 5.0% by weight of Si; up to 1.0% by weight of Ni; up to 2.0% by weight of Mo; and up to 16% by weight of Mn, the balance being substantially Fe, with the proviso that at least one of the following conditions is satisfied: the amount of C is higher than 0.3%, and/or the amount of Si is higher than 3.0% and/or the amount of Mn is higher than 9.0%. Moreover, the amounts of the above mentioned elements that are respectively known as ferrite formers (Cr, Mo, Si) and as austenite former (C, N, Co, Ni, Mn) and amongst said austenite and ferrite formers, the amount of each of these elements that are respectively known to increase and lower the stacking fault energy, are respectively selected and balanced so that at least 60% by weight of the alloy is, at ambient temperature, in a face centered cubic phase having a stacking fault energy low enough to show a fine deformation twinning under cavitation exposure or, alternatively, to make this face centered cubic phase transformable under cavitation exposure to a hexagonal close pack .epsilon.-phase and/or a .alpha.-martensitic phase showing such a fine deformation twinning.

Austenitic stainless steel with high cavitation erosion resistance

A soft, austenitic stainless steel alloy showing a high cavitation erosion resistance making it particularly useful for the manufacture and/or repair of hydraulic machine components. The alloy comprises from 8 to 30% by weight of Co; from 13 to 30% by weight of Cr; from 0.03 to 0.3% by weight of C; up to 0.3% by weight of N; up to 3% by weight of Si; up to 1% by weight of Ni; up to 2% by weight of Mo; and up to 9% by weight of Mn; the balance being substantially Fe. The amount of the above mentioned elements that are respectively known as ferrite formers (Cr, Mo, Si) and as austenite formers (C, N, Co, Ni, Mn) and, among said austenite and ferrite formers, the amount of each of the elements that are respectively known to increase and lower the stack fault energy, are respectively selected and balanced so that at least 60% by weight of the alloy is, at ambient temperature, in a metastable, face centered cubic phase having a stack fault energy low enough to make it capable of being transformed under cavitation exposure to a fine deformation twinning, hexagonal close pack .epsilon.-phase and/or .alpha.-martensitic phase.

Co containing austenitic stainless steel with high cavitation erosion

Method and device for quantitatively measuring the intensity of erosive cavitation present in an aqueous solution such as, for instance, fresh water. According to the method, a set of measuring electrodes is placed in the liquid, these electrodes including a reference electrode, at least one auxiliary electrode and at least one working electrode made of a metal selected from those capable of forming highly insulating oxide films capable of becoming thicker by ionic mobility under the action of an electric field, this metal being preferably titanium. The auxiliary and working electrodes are located in the zone where it is desired to measure the cavitation and a constant anodic voltage is applied across the working electrode by means of the auxiliary and reference electrodes. The intensity of the anodic current is then measured and any variation in the intensity of this current is detected and measured. The variation thus measured is, in terms of the appropriately selected constant anodic voltage applied, directly proportional to the intensity of erosive cavitation in the measure zone. This method as well as the device for carrying it out may particularly be useful in the design of hydraulic machines; during the testing of models or prototypes such as during tests on pumps, turbines, propellers or water valves, as well as for the supervision of machines in operation in hydraulic, thermo or nuclear plants, or in pumping stations for fresh or salt water.

Method and apparatus for detection of erosive cavitation in an aqueous

A circuit for controlling the power supply to an electrode of the shielded type, such as that used in a shielded metal arc welding process (SMAW) whereby to protect a user from electric shocks. The control circuit is a protection circuit which serves to protect welders against electric shocks by decreasing the circuit voltage between the electrode tip and the workpiece to be welded. An AC or DC power supply may be used to feed the electrode. The control circuit is comprised of a high impedance voltage source applied to the electrode, a detection circuit for determining the level value of the impedance appearing between the electrode and the workpiece. The detection circuit compares the impedance thus detected with a threshold impedance and generates a control signal when the detected impedance is lower than the threshold impedance. The control signal operates a driver circuit which energizes a power feed device serially connected between the electrode power supply and the electrode itself. The predetermined threshold impedance value is set at about 500 ohms whereby a wet human body will not be subjected to an electric shock by contacting the electrode and the workpiece simultaneously.

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St-Bruno, Canada

Raynald Simoneau