Surface hardening of machine tool guideways — common industrial method Machine tool guide ways are usually surface-hardened by which of the following processes to provide a hard wear layer on a tough substrate?

Introduction / Context:
Guideways on lathes, milling machines, and grinders must resist wear while maintaining geometric accuracy. A hard surface on a tough core is ideal. Several surface and through-hardening processes exist, but workshops traditionally select methods suited to large, long castings.

Given Data / Assumptions:

• Components are large cast iron or steel beds and slides.
• Need localized hardening without major distortion.
• Economical shop-floor process preferred.

Concept / Approach:
Flame hardening uses an oxy-fuel flame to heat the surface rapidly followed by spray quenching, creating a martensitic case with minimal through-heating. It is well suited to cast iron guideways and large components. Induction hardening is also widely used, especially on steels with adequate carbon, but flame hardening remains a classical and common choice for machine tool beds because of equipment reach and simplicity for large sections.

Step-by-Step Solution:
Identify constraints: large size, need for localized treatment, minimal distortion.Match process: flame hardening offers flexible coverage on long guideways.Therefore, select flame hardening as the usual process.

Verification / Alternative check:
Manufacturing references note flame-hardened cast iron ways as a standard practice, with hardness often in the mid-50s HRC range on the surface.

Why Other Options Are Wrong:

• Vacuum hardening: a through-hardening method for alloy steels, not ideal for massive beds.
• Martempering: quench technique to reduce distortion, not a localized surface process.
• Induction hardening: viable and used, but the conventional textbook answer for large guideways is flame hardening.
• Carburizing and quenching: diffusion case hardening suited to gears and low-carbon steels, not typical for cast iron guideways.

Common Pitfalls:
Assuming one method fits all; practical selection depends on workpiece size, material, equipment, and desired case depth.

Final Answer:
flame hardening