Tool materials: Stellite (cobalt-base alloy) preserves its hardness up to approximately what temperature?

Introduction / Context:
Hot (red) hardness indicates a tool material’s ability to retain hardness at elevated temperature. Stellite, a cobalt-based alloy with chromium and tungsten, bridges the gap between high-speed steels and carbides for heat resistance and wear properties in certain applications.

Given Data / Assumptions:

• Comparative ranges: HSS retains hardness roughly up to 550–650°C, stellite higher, straight carbides even higher (near 1000–1100°C depending on grade and binder).
• Conventional cutting without advanced coatings.

Concept / Approach:
Stellite grades exhibit very good hot hardness and abrasion resistance, retaining useful hardness up to about 850–900°C. This makes them suitable for high-temperature cutting of hard or scale-forming materials where HSS softens, though carbides usually surpass both for high-speed conditions.

Step-by-Step Solution:

Verification / Alternative check:
Toolmaterial data sheets list stellite hot-hardness resistance around the stated range, aligning with shop experience in hard, hot cutting tasks.

Why Other Options Are Wrong:
350°C/500°C: too low; even HSS exceeds these limits.1100°C: characteristic of certain carbides/ceramics rather than stellite.650°C: closer to HSS red-hardness region.

Common Pitfalls:
Confusing stellite with cemented carbide; overlooking that selection also depends on toughness, not only hot hardness.

Final Answer:

900°C