Alloying roles in high-speed steels (HSS) Assess the truth of the statement: “In high speed steels, vanadium adds to the property of red hardness and tungsten and chromium add to high wear resistance.”

Introduction / Context:
High-speed steels (HSS) retain hardness at elevated temperatures (“red hardness”) and resist wear due to stable carbide formers. Understanding the primary contributions of alloying elements guides selection of HSS grades for cutting tools.

Given Data / Assumptions:

• Typical HSS elements: W, Mo, Cr, V, Co.
• Red hardness refers to hot hardness retention during cutting.
• Wear resistance is linked to volume fraction and type of hard carbides (e.g., VC, M6C, M23C6).

Concept / Approach:
Tungsten and molybdenum are prime contributors to red hardness by stabilizing complex carbides and supporting secondary hardening during tempering. Cobalt also enhances hot hardness but does not form carbides. Vanadium primarily increases wear resistance and edge retention by forming hard, stable VC carbides and refining grain size. Chromium contributes to hardenability, corrosion/oxidation resistance, and forms M23C6 carbides, aiding wear resistance but is not the main source of red hardness. Therefore, the given statement misattributes roles, making it false.

Step-by-Step Solution:
Identify red-hardness drivers: W, Mo, and Co are key.Identify wear-resistance drivers: V (VC carbides) and Cr carbides contribute.Compare with statement: it assigns red hardness primarily to V and wear mainly to W and Cr—misleading.Therefore, mark the statement false.

Verification / Alternative check:
Tool steel datasheets and handbooks attribute hot hardness to W/Mo/Co systems and edge retention to vanadium carbides; performance trends across M and T series HSS corroborate this.

Why Other Options Are Wrong:
“True” contradicts accepted metallurgical roles; caveats about Mo or Co do not change the primary attributions.

Common Pitfalls:
Overgeneralizing that any strong carbide former automatically gives red hardness; the thermal stability of the matrix and secondary hardening behavior are crucial.

Final Answer:
False