Nitriding is a process of hardening steel by treating it in an atmosphere of

Options

A. `NH_(3)`
B. `N_(2)`
C. `O_(3)`
D. `H_(2)S`

Explanation

To solve the question regarding the process of nitriding and the atmosphere required for it, we can follow these steps:

### Step 1: Understand the Process of Nitriding
Nitriding is a heat treatment process used to harden steel. It involves the introduction of nitrogen into the surface of the steel to improve its hardness and wear resistance.

**Hint:** Nitriding is specifically aimed at enhancing the properties of steel through nitrogen infusion.

### Step 2: Identify the Atmosphere Used in Nitriding
The question lists several options: ammonia (NH3), nitrogen (N2), ozone (O3), and hydrogen sulfide (H2S). Among these, ammonia is known to be a common source of nitrogen for the nitriding process.

**Hint:** Think about which gas can provide nitrogen effectively for the hardening process.

### Step 3: Confirm the Role of Ammonia
In nitriding, ammonia (NH3) is dissociated to release nitrogen, which then diffuses into the steel surface. This process occurs at relatively low temperatures, allowing for the hardening of the steel without altering its core properties significantly.

**Hint:** Consider the chemical reactions involved in nitriding and how ammonia contributes to the nitrogen supply.

### Step 4: Analyze the Options
- **Ammonia (NH3)**: Correct, as it is used in the nitriding process.
- **Nitrogen (N2)**: While nitrogen is involved, it is not the direct source used in the process.
- **Ozone (O3)**: Not relevant to nitriding.
- **Hydrogen sulfide (H2S)**: Not used in nitriding.

**Hint:** Eliminate options that do not directly contribute to the nitriding process.

### Step 5: Conclusion
Based on the analysis, the correct answer to the question is that nitriding is a process of hardening steel by treating it in an atmosphere of ammonia (NH3).

**Final Answer:** Ammonia (NH3)