Mechanical Properties and Cutting Performance of Si ₃ N ₄ Ceramic Tools for CGI Turning at Different Speeds

ABSTRACT

The cutting performance and wear mechanisms of three types of Si ₃ N ₄ ceramic tools, namely, high‐hardness, high‐toughness/high‐strength, and high‐hardness/high‐toughness/high‐strength tools, were systematically investigated during compacted graphite iron (CGI) machining at cutting speeds of 200, 400, and 600 m/min. The results show that the dominant wear mechanism varies with cutting speed, resulting in different requirements for tool properties. Under low‐speed cutting conditions (200 m/min), abrasive wear dominates, and Si ₃ N ₄ ceramic tools with high hardness are more suitable. For medium‐speed cutting (400 m/min), intensified intermittent impacts promote fatigue spalling and adhesive wear, which act together with abrasive wear to accelerate tool failure; thus, tools combining high hardness, toughness, and strength are more appropriate. During high‐speed cutting (600 m/min), intensified oxidative wear and impact‐induced oxide‐layer spalling reduce wear resistance, making tools with superior toughness and strength essential for ensuring resistance to impact damage and fatigue chipping. This study provides a theoretical basis for selecting Si ₃ N ₄ ceramic tools under different CGI turning conditions.