טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEichenbaum Ari
SubjectSubsurface Thermal Damage for Aggressive Grinding of 17-4PH
Stainless Steel
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Emeritus Eli Altus
Professor Stephen Malkin
Full Thesis textFull thesis text - English Version


Abstract

The grinding process encompasses machining of components requiring smooth surfaces and precise tolerances (shallow grinding) or large material removals by one pass (Creep-feed grinding). Three main controlling parameters are: the depth of cut (a), the feed rate (vw) and the wheel velocity (vs).

The objective in this study is to find how the above parameters are related to the wheel wear, the consumed power, specific energy, surface temperatures, heat flux and energy partition, and most important, exploring thermal damage for aggressive grinding of 17-4 PH stainless steel. This material is commonly used for turbine blades in aerospace and power station industries.

Single pass straight grinding experiments were conducted with large depths of cut and various feed rates. The specific grinding energy was found to decrease toward a limit value as the removal rate was increased, except at very small removal rates where the opposite trend was observed.

At low removal rates, the maximum temperature estimated at the grinding zone was below the burnout limit of the cooling fluid, and no thermal damage was observed. The fraction of the grinding energy transported to the workpiece as heat was about 5%, which is consistent with previous findings.

At higher removal rates, much higher temperatures were found and thermal damage was observed in the form of a Heat Affected Zone (HAZ) with re-austenitization and re-hardening. The maximum HAZ temperature was about 900°C and insensitive to the grinding conditions.

The study proposes an optimal set of controlling parameters for aggressive grinding conditions which will cause minimum thermal damage.