PDLP Chapter 113 Should We Do It?
Chapter 113 Should We Do It?
"That's to be expected. If it were interesting, it would be something like a stand-up comedy routine."
Sun Deming shook his head and continued eating. This time, he ate a little faster.
The forty-second experiment began on a cloudy morning.
The sky over Beijing was overcast and the clouds hung low, like a soaked quilt covering the city, making it hard to breathe. There was no wind; the air was still. The locust tree leaves were motionless, as if frozen in place. The locust blossoms on the ground were also still, clinging to the ground, wet and beginning to turn black.
The laboratory was on the first basement level, where the sky was not visible, but Jiang Cheng could feel the oppressive atmosphere—the air was not flowing, and the ventilation ducts were louder than usual, buzzing like a swarm of bees flying, or like someone crying in the distance.
He fixed the simulation sample to the worktable of the spraying equipment and carefully inspected each air film hole.
The simulator wasn't a real blade, but a simplified specimen shaped like a thickened leaf, with twelve tiny holes on its surface, each 0.5 millimeters in diameter, almost invisible to the naked eye. He took a fine needle and probed each hole one by one. The needle was a sewing needle, very thin, and even passing it through the holes was difficult. He aimed the needle tip at the air film pore, gently poked it in, felt the tip touch the bottom, and then pulled it out. He repeated this action for each hole to confirm it was clear. Then he cleaned the surface of the simulator with acetone, wiping it repeatedly with cotton balls soaked in acetone until no black residue remained on the cotton balls.
Afterward, it was wiped with alcohol, rinsed with deionized water, and finally dried with compressed air. The compressed air hissed as it blew onto the surface of the simulation part, dispersing the residual liquid and leaving a dry, clean surface.
"Let's begin." Chief Engineer Chen stood behind him, holding a notebook with a blue cover that was even more worn, the corners curled into a curve.
Jiang Cheng took a deep breath and entered the parameters on the control panel. His finger moved across the buttons, pausing to confirm each number after pressing it. Powder feed rate: 6.5 grams per minute. Spraying distance: 105 millimeters. Substrate preheating temperature: 120 degrees Celsius. Current: 650 amperes. Argon flow rate: 40 liters per minute. Hydrogen flow rate: 7.5 liters per minute.
"Parameters confirmed," he said, his voice steady, but he could feel his heart racing.
"Confirmed," Chief Engineer Chen said.
He pressed the start button. The plasma spray gun hummed, louder than usual, as if in protest. The arc ignited, and a blinding white flame shot out, like a lightning bolt locked in the muzzle. He preheated the spray gun, aimed the nozzle at the copper plate beside it, and the flame burned for more than ten seconds, turning the surface of the copper plate black with a layer of oxide film. Then he moved the spray gun above the simulation part and pressed the powder feeding button.
The powder was fed into the flame, instantly melting into tiny droplets that impacted the surface of the simulation part at high speed. The crackling sound was denser than raindrops, like sand being sprinkled onto an iron plate. Jiang Cheng controlled the robotic arm, moving the spray gun back and forth across the simulation part's surface. One layer, two layers, three layers. Each movement was executed with the trajectory as consistent as possible, at a uniform speed and a constant distance.
His eyes were fixed on the spray gun, afraid to blink, lest he miss something. Sweat slid down his forehead, flowing into his eyes, stinging, but he dared not wipe it away.
The spraying was finished. He turned off the equipment and waited for the spray gun to cool down. The laboratory was quiet, with only the hum of the ventilation pipes and the faint crackling sound of the spray gun as it cooled—the sound of the metal contracting.
Sun Deming stood beside him, barely daring to breathe, his palms sweating so much that the pen holder was soaked. Huang Deqing squatted in the corner, holding nothing, his eyes fixed on the simulation, like a leopard waiting for its prey.
Jiang Cheng used tweezers to pick up the simulation part and placed it under the microscope. He adjusted the focus, and the image in the eyepiece went from blurry to clear. The coating surface was smooth, without any graininess, bubbles, or cracks. The grayish-white coating shimmered softly under the light, like a thin layer of porcelain. He moved the stage to examine different parts of the simulation part—the center, the edges, and the transitions between curved surfaces. The coating thickness was uniform, with no obvious differences in thickness. He used an eddy current thickness gauge to measure five points, and the readings were 298, 302, 295, 301, and 299 micrometers, respectively. The designed thickness was 300 micrometers, and all readings were within the tolerance range.
"The surface is acceptable," he said.
Chief Engineer Chen leaned closer and glanced at the microscope. Her brows were neither furrowed nor relaxed. Her lips were still pursed, but not as tightly. She straightened up, picked up a thin needle from the table, and began to examine the air pores. The first pore went in, clear. The second, clear. The third, clear. She examined them one by one, slowly, pausing to check each pore after inserting it. All twelve pores were clear. Her finger paused on the last pore, then she withdrew the needle.
"The permeability is acceptable." Her voice was flat, but Jiang Cheng noticed that when she finished checking the last hole, her fingers paused for a moment. It was a very short pause, less than a second, but he saw it.
"Next, we'll conduct a bonding strength test," Chief Engineer Chen said.
Bond strength testing is a destructive test. A coated specimen is glued to a pull-out head with a special adhesive, then placed on a tensile testing machine. A tensile force perpendicular to the coating surface is applied until the coating detaches. The bond strength is calculated by dividing the tensile force by the coating area. The unit is megapascals (MPa), but it is commonly expressed in newtons (N).
Jiang Cheng cut the simulated sample into strips, then into small squares five millimeters wide and ten millimeters long. Each small square was cleaned with acetone and glued to the pulling head with a special adhesive. The adhesive was epoxy resin, which required heating and curing; he baked it in an oven for an hour. After an hour, he took out the sample and let it cool to room temperature. Then he fixed it on the tensile testing machine.
The tensile testing machine was a bulky piece of equipment, with a cast iron body painted dark green, featuring a handwheel and an analog dial. Jiang Cheng slowly turned the handwheel, moving the pull head upwards to apply tension. The pointer moved in small increments: 100 Newtons, 200 Newtons, 300 Newtons. The standard for the coating was 350 Newtons. At 350 Newtons, the coating did not peel off. He continued adding, 400 Newtons, 450 Newtons. The coating still did not peel off. When the pressure reached 500 Newtons, the substrate of the simulated part began to deform, with the edges slightly lifting, but the coating remained adhered, without peeling or cracking.
"It exceeds the standard," Sun Deming whispered from the side, his voice filled with barely suppressed excitement.
Jiang Cheng didn't speak, and continued adding oil. Six hundred Newtons, and the coating still hadn't peeled off. The substrate had bent, like a bow. He stopped.
"Should we add it?" he asked Chief Engineer Chen.