What is claimed is:
1. A metallic material that can be worn away by abrasion, the material principally consisting of a metal alloy based on nickel andor cobalt which is (quasi) free of oxide or of a ceramic; said metal alloy or said ceramic having:
particles of solid lubricant distributed through its volume, in an amount that is 10% by volume or more; andor
closed pores distributed through its volume, said pores endowing said material with a porosity that is less than a percolation threshold; andor
recesses distributed in its surface, the walls of which are intended to undergo wear by abrasion.
2. The material according to claim 1, wherein said metal alloy or said ceramic has particles of solid lubricant and closed pores distributed through its volume.
3. The material according to claim 1, wherein said metal alloy or said ceramic has:
particles of solid lubricant and closed pores distributed through its volume; and
recesses distributed at its surface, the walls of which are intended to undergo wear by abrasion.
4. The material according to claim 1, consisting of an NiCrAl type metal alloy or a MCrAlY type metal alloy in which MNi andor Co.
5. The material according to claim 1, consisting of a ceramic based on zirconia (ZrO2), alumina (Al2O3) or silicon carbide (SiC).
6. The material according to claim 1, wherein the equivalent diameter of said particles of solid lubricant is in the range 5 m to 100 m.
7. The material according to claim 1, wherein said particles of solid lubricant consist of particles of boron nitride (BN) or graphite, said boron nitride (BN) not being used in a metal alloy containing nickel (Ni).
8. The material according to claim 1, wherein the equivalent diameter of said closed pores is in the range 10 m to 150 m.
9. The material according to claim 1, wherein the porosity of said metal alloy or said ceramic is 10% to 50% by volume.
10. The material according to claim 1, wherein the equivalent diameter of said surface recesses is in the range 0.5 mm to 3 mm.
11. The material according to claim 1, wherein said metal alloy or said ceramic comprises particles of a brazing material in an effective quantity, such that it is self-brazable.
12. The material according to claim 11, wherein said brazing material consists of silicon (Si) andor boron (B)
13. Parts, in particular of the flat or curved plate type, formed from a material according to claim 1.
14. Casings intended to contain revolving parts at high temperatures, wherein their inner surfaces are at least partially covered with plates according to claim 13 affixed to their inner surfaces by brazing or self-brazing.
15. A process for producing a material according to claim 1, the process comprising:
forming an intimate mixture of a powder of the metal alloy or the ceramic in question and an organic binder; said intimate mixture optionally additionally including an effective quantity of particles of solid lubricant andor particles of brazing material;
molding said mixture by pressing or injection into a mold which optionally exhibits protuberances that can generate surface recesses;
extracting the molded blank from said mold;
unbinding said unmolded blank;
at least partial densification by sintering of said blank following unbinding; said densification being carried out in a nonoxidizing atmosphere for the blank based on a metal alloy;
said particles of solid lubricant andor said mold protuberances andor carrying out partial sintering endowing the material with the desired abradability; said particles of brazing material, if used, rendering it self-brazable.
16. The process according to claim 15, wherein said metal alloy powder is constituted by grains with an equivalent diameter in the range 10 m to 70 m.
17. The process according to claim 15, wherein said ceramic powder is constituted by grains with an equivalent diameter in the range 1 m to 20 m.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of operating an agricultural vehicle to reduce the time taken for rotating components of the crop processing machinery driven by the vehicle engine to reach a standstill, which method comprises the steps of:
sensing when a signal is generated by the vehicle operator to disengage a drive from the engine to the rotating components;
reducing the engine speed in response to the sensed signal to a minimum value below a steady idling speed of the engine;
disengaging the drive to the rotating components after the engine speed has reached the said minimum value; and
increasing the engine speed to a value equal to or greater than the steady idling speed after the disengagement of the drive to the rotating components.
2. The method of claim 1, further comprising the step of emitting an audible alarm signal while components of the processing machinery are still rotating, the signal having a characteristic that varies with the speed of rotation of the components.
3. The method of claim 2, wherein the pitch of the audible signal varies with the speed of rotation of the components of the crop processing machinery.
4. The method of claim 2, wherein the pulse repetition frequency of the audible signal varies with the speed of rotation of the components of the crop processing machinery.
5. The method of claim 3, wherein the pulse repetition frequency of the audible signal varies with the speed of rotation of the components of the crop processing machinery.