Method for solution hardening of a cold deformed workpiece of a passive alloy, and a member solution hardened by the method

摘要

The invention relates to a method for method for formation of expanded austenite and/or expanded martensite by solution hardening of a cold deformed workpiece of a passive alloy, which method comprises a first step of dissolving at least nitrogen in the workpiece at a temperature T1, which is higher than the solubility temperature for carbide and/or nitride and lower than the melting point of the passive alloy, and a subsequent second step of dissolving nitrogen and/or carbon in the work piece at a temperature T2, which is lower than the temperature at which carbides and/or nitrides form in the passive alloy. The invention further relates to a member, such as a lock washer for securing bolts or nuts prepared using the method.

主权项

1. A method for formation of expanded austenite and/or expanded martensite by solution hardening of a cold deformed workpiece of a passive alloy based on iron, nickel and/or cobalt and comprising at least 10% chromium, which method comprises a first step of dissolving at least nitrogen using N2 gas in the workpiece at a temperature T1, which is at least 1050° C. and lower than the melting point of the passive alloy, wherein dissolution of nitrogen at temperature T1 is performed to obtain a diffusion depth in the range of 50 pm to 5 mm, and a subsequent second step of dissolving nitrogen and/or carbon in the workpiece at a temperature T2 in the range of 300° C. to 550° C., the method further comprising the intermediate step of cooling the workpiece after the dissolution step at temperature T1 to a temperature which is lower than a temperature at which carbides and/or nitrides form in the passive alloy, wherein the cooling from the temperature 900° C. to 700° C. is performed in less than 60 seconds, wherein the hardness of an expanded austenite zone or an expanded martensite zone is at least 1000 HV.