Experimental Study on Performance Evaluation and Effect of Cobalt content in Cryogenic Treated Cemented Carbide Tool Material

Abstract

Machining of metals that has superior mechanical properties require newlineadvanced tool materials with exceptional properties. Coating and alloying are the newlinetraditional methods that improve the life of the tool. But the processes are newlinecomplex and expensive. So, tool manufacturers are in search of a simple and cost- newlineeffective technique that can improve the properties of the tool. Literature shows that cryogenic treatment has a positive influence on the newlineperformance of conventional tool materials like steel and its alloys. In Steel, the newlinetransformation of retained austenite and precipitation of secondary carbide are the newlinekey mechanisms responsible for the performance improvement. In tungsten newlinecarbide, densification of cobalt binder and formation of eta (and#951;) carbides are the newlinelikely phenomenon reported. But some literature contradicts these findings and newlinereports that cryogenic treatment has no impact on the tungsten carbide tools. This newlineshows that research in the cryogenic treatment of cemented carbide is with newlineuncertainties which need a comprehensive study. Hence, in this study, attempts had been made to study the performance of newlinecryogenic treated cemented carbide tools with focus on tools with 6%, 9% and newline25% cobalt content. Uncoated samples were selected to avoid variables like newlinecoating thickness and coating uniformity. The inserts were subjected to cryogenic treatment (CT) and cryogenic treatment and tempering (CTT). Tempering was newlineperformed to relieve the internal stress formed during the process. Turning tests were conducted on steel and cast iron with 6% and 9% cobalt newlinegrades, at 100 m/min and 125 m/min cutting speeds. At both the selected cutting newlinespeeds, cryogenically treated inserts and cryogenic treated and tempered inserts newlineshowed comparatively lesser flank and nose wear than the untreated inserts. Cemented carbide samples with 25% cobalt were exclusively made for the newlinestudy. As, such high-cobalt grade cannot be rotational speeds.