Chapter 15 - Surface Hardening

Question 1

What is the purpose of surface hardening?

Answer 1

It helps to create a thin hardened water resistant layer on the surface of a material, maintaining a soft and ductile inner core.

Question 2

Why is surface hardening commonly called case hardening?

Answer 2

Surface hardening is commonly called case hardening because a hard metal case protects an unhardened core

Question 3

Name four different applications or components that require surface hardening.

Answer 3

• Bearings,
• piston pins,
• crankshaft and
• cams

Question 4

Describe the differences between carburizing and nitriding?

Answer 4

Carburizing is the process that puts carbon on the surface while nitriding injects nitrogen to the surface.

Question 5

What two surface-hardening processes use the principles of localized heating?

Answer 5

Flame hardening and

Induction hardening.

Question 6

Explain the process of pack carburizing?

Answer 6

It is the oldest and most basic surface hardening process where the parts to be hardened are packed into a metal box along with a carbonaceous material and heated.

Question 7

Name two advantages gas carburizing has over pack carburizing?

Answer 7

It is a faster process, and it requires less physical labor and handling.

Question 8

What type of carbon-rich liquid is typically used in liquid carburizing?

Answer 8

A molten salt bath is typically used in liquid carburizing.

Question 9

Of all the surface-hardening processes, which one is capable of producing the hardest case?

Answer 9

Nitriding.

Question 10

What range of heating temperatures is typically used in nitriding?

Answer 10

900-1000C

Question 11

What is carbonitriding?

Answer 11

It is the gaseous process that introduces both carbon and nitrogen to steel parts.

Question 12

Which surface-hardening process uses liquid to impregnate the surface of steel with carbon and nitrogen?

Answer 12

Cyaniding (Liquid Carbonitriding)

Question 13

What two surface-hardening processes do not involve the addition of wither carbon or nitrogen to steel?

Answer 13

• Flame hardening,

- induction hardening

Question 14

Explain the advantages of flame hardening over surface-hardening process.

Answer 14

• Inexpensive,
• more controlled, and
• case depth.

Question 15

What is the main disadvantage of cyaniding?

Answer 15

Very hazardous,

cyanide salts are poisonous.

Question 16

In induction hardening, what is the source of electromagnetic induction?

Answer 16

The source of electromagnetic induction is the coil of wire that surrounds the surface.

Question 17

Which surface-hardening process is considered to be the most accurate?

Answer 17

Induction hardening.