'The Effects of Processing Parameters on Microstructure and Properties of Laser Deposited PM Alloy 690N_2 Powder'

摘要

Powder Metallurgy (PM) Alloy 690N_2, the PM derivative of Inconel 690 (IN 690), has been shown to have a higher elevated temperature yield strength and superior stress corrosion cracking (SCC) resistance than conventionally processed IN 690. The property improvements seen in Alloy PM 690N_2 are due to interstitial nitrogen strengthening and precipitation hardening resulting from the formation of fine Titanium/ Chromium - nitrides. The application of Alloy PM 690N_2 has had limited use due to the high costs involved in producing wrought products from powder. Laser Powder Deposition (LPD) offers another technique to take advantage of PM 690N_2 properties. Three different variations of the Alloy 690 chemistry have been deposited, PM chemistry - nitrogen atomized (PM 690N_2), Ingot Metallurgy (IM) chemistry - nitrogen atomized (IM 690N_2), and IM chemistry - argon atomized (IM 690Ar). The microstructural and mechanical property variations of these LPD deposited materials are reported. Alloy PM 690N_2 powder was laser deposited at rates from.1 to over 12 cubic inches per hour at laser input powers ranging from 250 to 5000 watts using both CO_2 and Nd:YAG lasers. In all cases a fully dense material has been produced. There is a question however of how the properties of this material respond over such a wide range of parameters. An attempt has been made to correlate the processing conditions with the resultant microstructures and properties. The effects of LPD on the microstructural features and properties of Alloy PM 690N_2 are discussed.