Machining of CrNiCo alloys (chromium-nickel-cobalt)

The machining of CrNiCo alloys is particularly challenging due to their unique physical properties. The main factors that determine the machinability of these alloys are

Work hardening: CrNiCo alloys have a strong tendency to work harden during machining, which means that the material becomes harder as a result of the cutting process. This makes subsequent cuts more difficult and accelerates tool wear.

Heat generation and low thermal conductivity: Due to high strength and plastic deformation, an excessive amount of heat is generated in the cutting zone. CrNiCo alloys conduct heat poorly, which leads to localized temperature increases. The heat is concentrated at the tool-workpiece interface, which impairs both the service life of the tool and the workpiece quality.

Tool material and wear: The combination of high hardness, toughness and heat bonding in CrNiCo alloys leads to rapid tool wear and possible tool failure. The choice of cutting material (e.g. coated carbides or ceramics) is critical and may require frequent tool changes.

Cutting forces: The strength and toughness of these alloys require high cutting forces. Stable machine structures and powerful spindles are required to ensure dimensional accuracy and surface quality.

Cutting parameters and cooling lubricant: Optimization of cutting speeds, feed rates and cutting depths is essential. Lower speeds and higher feeds are often recommended. The use of optimally adjusted high-pressure coolant is crucial for heat dissipation and chip removal.

Surface quality and tool adhesion: The tendency of CrNiCo alloys to adhere to the tool (built-up edge formation) worsens the surface quality and also increases tool wear, especially with inadequate cooling or unsuitable tool geometries.

Summary: Careful planning, suitable tool selection, optimum cutting parameters and efficient coolant supply are essential for the successful machining of CrNiCo alloys.