Components of a rotary piston machine

Abstract

The friction surface of a cast iron side wall member for a rotary piston engine is hardened by iontriding in an electrical glow discharge in a gas atmosphere containing nitrogen, after coating the areas not to be hardened, to inhibit glow discharge at those areas.

What is claimed is: .[.1. A trochoid housing for a rotary piston machine, made of cast iron and provided with ionirided hardened areas limited to the wiped surfaces; charcterized in that the hardened areas throughout the wiped areas are provided with an iron nitride zone reduced to less than 10 microns thickness, with a surface roughness not exceeding R a  = 0.8 micron, with a corrosion resistance relative to fuel combustion residues increased by at least 300 percent, with a thermal resistance up to 500°C over long periods and, respectively, up to 800°C over short periods and with a ductility reduced by not more than 10 percent as compared to the basic material..]. .[.2. A method of producing a cast iron trochoid housing for a rotary piston machine in which ionitriding is performed by means of an electrical glow discharge in a gas atmosphere containing nitrogen at elevated temperature in a treatment chamber, the said housing being provided with means inhibiting the electrical glow discharge on the surfaces outside the wiped areas proper prior to ionitriding, characterized in that the said areas are ionitrided after insertion in the treatment chamber during at least 5 hours at a gas pressure in the range of 0.1 - 5 mmHg and an operating voltage of more than 500 volts, the operating voltage and the gas pressure being so controlled that the sputtering of metal particles from the surface of the wiped areas partly reduces the iron nitride zone and keeps it below 10 microns..]. .Iadd. 3. Trochoid housings, side and central units for a rotary piston machine, made of a material selected from the group consisting of iron and steel, particularly cast iron, and provided with ionitrided hardened areas limited to the wiped surfaces; characterized in that the hardened areas throughout the wiped areas are provided with an iron nitride zone reduced to less than 10 microns thickness, with a surface roughness not exceeding R a  = 0.8 micron, with a corrosion resistance relative to fuel combustion residues by at least 300 per cent, with a thermal resistance up to 500°C over long periods and, respectively, up to 800°C over short periods and with a ductility reduced by not more than 100 per cent as compared to the basic material. .Iaddend..Iadd. 4. A method of producing trochoid housings, side and central units for a rotary piston machine made of a material selected from the group consisting of iron and steel in which ionitriding is performed by means of an electrical glow discharge in a gas atmosphere containing nitrogen at elevated temperature in a treatment chamber, said trochoid housings, side and central units being provided with means inhibiting the electrical glow discharge on the surfaces outside the wiped areas proper prior to ionitriding, characterized in that the said areas are ionitrided after insertion in the treatment chamber during at least 5 hours at a gas pressure in the range of 0.1 - 5 mmHg and an operating voltage of more than 500 volts, the operating voltage and the gas pressure being so controlled that the sputtering of metal particles from the surface of the wiped areas partly reduces the iron nitride zone and keeps it below 10 microns. .Iaddend.