Low temp carbonitrided coatings - on iron alloys using partly dissociated ammonia at mos

摘要

The coatings are formed in an atmos. of partly, i.e. 35-90% dissociated NH3 at 550-750 degrees C, opt. with the addn. of 20-90% gas with high N2 and low H2 content, opt. 5-50% air or 0.2-10% O2, opt. 0.5-15% H2O vapour or 5-60% CO2 or other components contg. oxygen in amt. equiv. to 5-50% air. The carbonitrided coating, having a carbonitride or oxycarbonitride structure, is satd. with C during carbonitriding from the core of the carbonitrided Fe alloy contg. is not 0.1% C. The coating gives high resistance to (semi)dry abrasion and improves fatigue strength and contact fatigue resistance. Carbonitrides with relatively low thermodynamic activity are obtd. facilitating the diffusion of C from the core and giving good hardness, sliding properties and wear resistance. The core pref. consists of constructional steel with >0.1% C content or a pearlitic alloy.