Abstract: A sliding member is sulphonitride by heating at 480.degree.-600.degree. C. in the presence of both 10-500 ppm of a hydrogen sulfide gas and a 20-70 vol % ammonia gas, or by a method which comprises performing a primary heat treatment on the sliding member at 450.degree.-540.degree. C. in the presence of 50-200 ppm of a hydrogen sulfide gas and a 10-70 vol % ammonia gas, then ceasing the supply of the ammonia gas, slowly reducing the temperature to a level of 200.degree.-350.degree. C., and performing a secondary heat treatment at that temperature level. By the either method, the sliding member having a FeS.sub.2 on its topmost surface can be obtained.

Abstract: A sliding member having a layer of FeS.sub.2 on its surface is formed by sulphonitriding the member by heatint it at 480.degree. C.-600.degree. C. in the presence of both 10-500 ppm of a hydrogen sulfide gas and 20-70 vol % ammonia gas. An alternate heating method involves performing a primary heat treatment on the sliding member at 450.degree.-540.degree. C. in the presence of 50-200 ppm of a hydrogen sulfite gas and a 10-70 vol % ammonia gas, then ceasing the supply of the ammonia gas, slowly reducing the temperature to between 200.degree.-350.degree. C., and performing a secondary heat treatment at that temperature level.

Abstract: A quenching method wherein an object to be quenched is sprayed with a mixed spray jet of a liquid and a gas. The diameter of droplets in the mixed spray jet is from 50 to 200 .mu.m, and the mixing ratio between the liquid and the gas is varied during the period from the start to the end of cooling. Also disclosed is a quenching apparatus having nozzles for spraying an object to be quenched with a mixed spray jet of a liquid and a gas, a liquid supply source for supplying a pressurized liquid, and a gas supply source for supplying a pressurized gas. Each of the nozzles has a liquid-jetting port formed in the surface opened to the atmosphere and a gas-jetting port annularly formed around the liquid-jetting port on the same plane. The liquid-jetting port is communicated with the liquid supply source, while the gas-jetting port is communicated with the gas supply source.