The lanthanum influence on quality and operational properties of single crystal nickel base ZhS36-VI superalloy
The harmful influence of sulfur and phosphorus on heat resistant properties of ZhS36-VI alloy during stress rupture test on long base testing (500 and more hours) as well as on middle quantity of cycles to rupture upon MCF wasdetermined. The possibility to reduce the content of harmful influence of sulfur and phosphorus impurities or their neutralization through microalloing by lanthanum that positively influence on alloy properties recovery was investigated. The mechanism of lanthanum addition for neutralization of these impurities harmful influence was suggested whereby sulfur removes from the melt as refractory lanthanum sulfides by their adhesion on crucible walls during melting and on foam filter during casting. In contrast to sulfur the refractory phosphides with lanthanum don’t remove from the melt. The properties comparison of single crystal alloy cast on units of low- and high gradient direct solidification UVNK-9A and UVNS-5 is presented.